Service Manual For Yuchai Diesel Engine.pdf

Service Manual for WD10 Mechanical Pump Series Engine

YUCHAI Engine Service Manual

Preface All technical information and pictures in this manual are based on Operation and Maintenance manual of YUCHAI products, part drawings, and design and manufacturing technics of YUCHAI products. This manual introduces disassembling and assembling process of YUCHAI engine, provides service technologies and technical requirements of diesel engine to help serviceman profoundly understand disassembly and assembly methods of the engine, also lays a solid technical foundation for serviceman to do troubleshooting. This manual is organized as follows: Chapter 1

General

This chapter mainly introduces precautions for maintenance of the diesel engine, significance of all kinds of symbols used in this manual and tightening torque of common bolts. Chapter 2

Disassembly of Diesel Engine

This chapter tells the serviceman/user how to disassemble each component by step correctly, and precautions need to be noted during the disassembly. Chapter 3

Assembly of Diesel Engine

This chapter tells the serviceman/user how to assemble each component step by step correctly, and precautions need to be noted during the assembly. Chapter 4

Inspection & Debugging

Chapter 5

Diagnosis and Elimination of Engine Common Faults

This chapter introduces diagnosis and elimination of engine common faults. Chapter 6

Engine Parameters

ATTENTION The parts and components that mentioned in this manual may change along with product improvement, but we do not promise to inform the changes of products that have been sold, please consult or ask Shandong Lingong Construction Machinery Co. Ltd for the updated details.

YUCHAI Engine Service Manual 880×1230 mm

16#

1st Edition in 2014. 7

18pieces 1st Print

SHANDONG LINGONG CONSTRUCTION MACHINERY CO.，LTD Address: Linyi Economic Development Zone Tel: 86-0539-8785688 Fax: 86-0539-8785698 Postal code：276023 Website：www.sdlg.cn Services Tel：8008607999 4006587999 0539-8785800 Services Fax：86-0539-8785671

YUCHAI Engine Service Manual

CONTENTS 1 General.................................................................................................................... 1 11 Safety Precautions .................................................................................................. 1 12 Marks ...................................................................................................................... 4 13 Tools and Gauges ................................................................................................... 4 14 Application of YUCHAI Engine ............................................................................ 5 15 Composition and Significance of YUCHAI Engine Model ................................... 5 2 Disassembly of Diesel Engine ................................................................................ 6 21 Disassembly of Outer Parts .................................................................................... 6 211 Disassembly of Crankcase Ventilation Device .............................................. 6 212 Disassembly of Fan ........................................................................................ 6 213 Disassembly of Turbocharger......................................................................... 7 214 Disassembly of Silencer, Exhaust Pipe and Water Outlet Pipe ..................... 7 215 Disassembly of Air Filter ............................................................................... 8 216 Disassembly of High Pressure Fuel Pipe ..................................................... 10 217 Disassembly of Fuel Coarse Filter ............................................................... 11 218 Disassembly of Hand Fuel Pump ................................................................. 11 219 Disassembly of Fuel Fine Filter ................................................................... 12 2110 Disassembly of Engine Oil Inlet/Return Pipe of Fuel Injection Pump13 2111 Disassembly of Transmission Belt and Generator Assembly ............. 14 2112 Disassembly of Fuel Injection Pump Assembly ................................. 15 2113 Disassembly of DC Starter Motor ....................................................... 16 2114 Disassembly of Engine Oil Cooler...................................................... 16 2115 Disassembly of Water Pump Assembly .............................................. 17 2116 Disassembly of Pulley Damper ........................................................... 17 22 Disassembly of Cylinder Cover Components ...................................................... 19 221 Disassembly of Cylinder Cover Shield ........................................................ 19 222 Disassembly of Rocker arm Assembly ........................................................ 20 223 Disassembly of Fuel Injector ........................................................................ 22 224 Disassembly of Valve Lock Clamp, Valve Spring and Valve ..................... 23 225 Disassembly of Cylinder Cover.................................................................... 24

YUCHAI Engine Service Manual

23 Disassembly of Gear Housing and Camshaft ....................................................... 25 231 Disassembly of Gear Housing ...................................................................... 25 232 Disassembly of Camshaft ............................................................................. 25 233 Disassembly of Idle Gear and Idle Gear Shaft ............................................. 26 234 Disassembly of Air Compressor and Air Compressor Idle Gear ................. 28 24 Disassembly of Engine Oil Sump, Engine Oil Strainer and Engine Oil Pump .... 30 241 Disassembly of Engine Oil Sump ................................................................. 30 242 Disassembly of Engine Oil Strainer ............................................................. 31 243 Disassembly of Engine Oil Pump ................................................................. 31 25 Disassembly of Flywheel and Flywheel Shell...................................................... 33 251 Disassembly of Flywheel.............................................................................. 33 26 Disassembly of Piston Connecting Rod, Crankshaft and Cylinder Sleeve .......... 34 261 Disassembly of Piston Connecting Rod ....................................................... 34 262 Disassembly of Crankshaft ........................................................................... 35 263 Disassembly of Cylinder Sleeve ................................................................... 37 3 Assembly of Diesel Engine .................................................................................. 39 31 Selection of Cleaning Fluid .................................................................................. 39 311 Cleaning of Oil Dirt ...................................................................................... 39 312 Removal of Carbon Deposit ......................................................................... 40 313 Removal of Water Scale ............................................................................... 41 314 Removal of Rust ........................................................................................... 42 32 Assembly of Engine Block ................................................................................... 43 321 Cleaning of Engine Block............................................................................. 43 322 Inspection of Engine Block .......................................................................... 44 323 Assembly of Engine Block ........................................................................... 48 324 Elimination of Engine Block Common Faults ............................................. 53 33 Assembly of Crankshaft ....................................................................................... 56 331 Cleaning of Crankshaft ................................................................................. 56 332 Inspection of Crankshaft ............................................................................... 56 333 Assembly of Crankshaft ............................................................................... 59 334 Maintenance of Crankshaft ........................................................................... 63 34 Assembly of Piston Connecting Rod Assembly ................................................... 66 341 Cleaning of Piston Connecting Rod Assembly ............................................ 66 342 Inspection of Piston Connecting Rod Assembly .......................................... 67

YUCHAI Engine Service Manual

343 Assembly of Piston Connecting Rod Assembly .......................................... 69 344 Common Faults of Piston Connecting Rod Assembly ................................. 74 35 Assembly of Engine Oil Pump ............................................................................. 76 351 Cleaning of Engine Oil Pump....................................................................... 76 352 Inspection of Engine Oil Pump .................................................................... 76 353 Assembly of Engine Oil Pump ..................................................................... 79 354 Common Faults of Engine Oil Pump ........................................................... 79 355 Assembly of Engine Oil Cooler ................................................................... 80 36 Assembly of Gear Housing Cover Plate, Camshaft, Idler Shaft and Gearing Housing ................................................................................................................. 82 361 Assembly of Gearing Housing Cover Plate ................................................. 82 362 Assembly of Camshaft and Camshaft Gear ................................................. 82 363 Assembly of Idler Shaft and Timing Gear ................................................... 84 364 Assembly of Gear Housing .......................................................................... 87 37 Assembly of Air Compressor ............................................................................... 88 371 Cleaning of Air Compressor ......................................................................... 89 372 Inspection of Air Compressor ...................................................................... 89 373 Installation of Air Compressor ..................................................................... 89 374 Common Faults of Air Compressor ............................................................. 90 38 Assembly of Fuel Injection Pump ........................................................................ 92 381 Cleaning of Fuel Injection Pump .................................................................. 92 382 Inspection of Fuel Injection Pump ............................................................... 92 383 Installation of Fuel Injection Pump .............................................................. 93 384 Common Faults of Fuel Injection Pump ...................................................... 96 385 Installation of Fuel Injection Pump Timing Gear ...................................... 101 39 Assembly of Damper .......................................................................................... 103 310 Assembly of Engine Oil Sump and Components Inside ............................ 105 3101 Oil Strainer Assembly ....................................................................... 105 3102 Assembly of Engine Oil Sump .......................................................... 105 311 Output End Components (Flywheel, Clutch and Flywheel Shell) ............. 106 3111 Flywheel and Gear Ring Assembly .................................................. 106 3112 Clutch ................................................................................................ 106 3113 Installation of Flywheel Shell ........................................................... 107 312 Assembly Of Cylinder Cover and Its Parts ................................................ 109 313 Assembly Of Water Pump, Fan and Steering Pump .................................. 124 314 Assembly of A/C Generator and Starter Motor ......................................... 129

YUCHAI Engine Service Manual

315 Assembly of Intake and Exhaust Pipes and Turbocharger ......................... 134 316 Assembly of Intercooler ............................................................................. 140 317 Assembly of Fuel Filter, Engine Oil Filter, Fuel Cut-off Solenoid Valve and Other Components .............................................................................................. 142 4 Inspection & Debugging ..................................................................................... 144 41 Inspect Engine Parts and Components for Intactness and Fastening Condition 144 42 Inspection of New Engine .................................................................................. 146 43 Testing of Engine Technical Indexes ................................................................. 149 5 Diagnosis and Elimination of Engine Common Faults ...................................... 151 51 Diagnosis and Analysis of Engine Faults ........................................................... 151 52 Engine Common Faults ...................................................................................... 154 53 Emergency Handling Methods for Engine Common Faults .............................. 172 6 Engine Parameters .............................................................................................. 173 61 Engine Technical Parameters ............................................................................. 173 62 Fitting Clearance of Main Parts and Components .............................................. 182 63 Tightening Torque of Main Bolts ....................................................................... 196

YUCHAI Engine Service Manual

1 General 11 Safety Precautions Important Safety Notes Maintenance and repair is vitally important for safety operation of the machine. This manual mainly expounds techniques about how to correctly disassemble and assemble the machine. To protect related personnel against injury, this manual uses

as safety label, for

precautions marked with this label, please be careful during the operation and must never on any account be negligent. For operations that possible dangers are involved, firstly pay attention to your own safety and necessary security measures shall be taken.

Safety Tips In the process of assembly and disassembly, wrong operation method may damage the parts or components, shorten the service life and deteriorate the performance of the machine, even brings potential safety hazard. Therefore, when assembling and disassembling the components, please read related content in this manual carefully. Disassembly: 1.

Choose suitable site for the disassembly, standard service shop is preferred, and at least choose clean cement floor. If the disassembly has to be done in the field, you must use wood board or hardboard to place the removed parts, in order to keep the parts clean and protect them from contamination and lost.

2.

Drain out all engine oil and coolant (pay attention to prevent pollution of the environment), clear away the dust and oil dirt on the machine.

3.

Pay attention to operation procedures and methods, use the tools correctly and apply your strength wisely. Follow the disassembling steps strictly and do not strike or pry the machine at will, to avoid damaging the parts or tools.

4.

Place the removed parts reasonably: It’s better to use parts rack, at least place the parts on clean wood block. Pairing parts (such as connecting rod, piston, bearing shell, shaft cap and injector) should be placed orderly and marked in pair, the joint of some important parts should be covered with dust cap. Parts of each cylinder should be placed together orderly, so that no more 1

YUCHAI Engine Service Manual running-in is needed after reassembly. It’s better to assemble the nuts and screws to their original positions, to avoid misplacement or lost. 5.

For part that cannot be disassembled easily due to wrong operation or serious rust, try to take assist measures: wet the part with engine oil or diesel oil, or heat the part, or attach adapter by welding.

6.

In the process of disassembly, always pay attention to personnel safety and equipment safety. Pay special attention to fire safety.

Assembly: 7.

Strictly comply with processes and steps specified in related technical documents to perform the assembly.

8.

Each part should be rinsed and inspected by visual before assembling, the part should be free of sand hole, flash and blur, and no crack, bumping damage, corrosion, residual sealant and other defect is allowed.

9.

All oil galleries, oil chambers, water channels and deep holes of each part should be clean and free of any residue.

10. All parts must have a certification or proof mark. Old part must be inspected and proved qualified before reuse. 11. When assembling, pay attention to the mark of pairing parts. 12. Pay attention to special assembling requirements of connectors, safety locking plate and sealing devices. For parts with tightening torque requirements, the specified tightening order and tightening torque should be strictly complied with. For parts that connected with two or more bolts/nuts, the bolts or nuts should be tightened evenly and crosswise in two or more steps. In addition to special requirements, choose tightening torque according to table 1-1. Table 1-1 Reference table for tightening torque of common bolts Bolt (mm)

specification

Tightening (Nm) Bolt (mm)

torque

specification

Tightening (Nm)

torque

M6

M8

M10

M12

M14

M16

10-20

20-30

30 -40

60-70

120-140

180-200

Z1/8

Z1/4

Z3/8

Z1/2

Z3/4

Z1

8-14

24-34

47-68

47-68

68-95

88-102

13. In the process of assembling, adjusting or parameter measuring should be performed by complying with requirements in operation manual or related maintenance documents. 14. In the process of assembling, if incorrect structure or installation is found and modification is 2

YUCHAI Engine Service Manual necessary, please be sure to ask the manufacturer for permission or consult professionals in advance, do not alter it at will. 15. Choose sealant reasonably. Specifications for sealant selection and application: (1) The sealing surface and thread should be clean and free of oil dirt before applying sealant. (2) Thread sealant (262, 242 sealant) is suitable for locking of thread, also exerting a part of sealing effect. The sealant should be applied on mid-front area of the effective contact section of the thread. (3) Pipe thread sealant (545 sealant) is suitable for sealing and locking of tapered thread (NPT) on pipe, pipe joint and plug screw. The sealant should be applied on mid-front area of the effective contact section of the thread. (4) Bowl-shape plug sealant (11747 sealant), the sealant should be applied on effective section of sealing tape, make sure the sealant is evenly distributed and without discontinuity. (5) Sealing gasket sealant (515 sealant) is suitable for plane (with or without gasket). the sealant should be applied on inner side of gasket hole, sealant trace should be continuous and with width of 1~2mm. Under special requirements, it is allowed to apply two sealant traces. (6) Before tightening the plug, joint or bolt that is applied with sealant, be sure screw-in the sealant part by hand firstly. When applying the sensor transition joint with sealant, make sure the sealant is evenly applied on middle-rear part of the joint thread and no sealant on the sensing end. 16. Spare parts must come from the original manufacturers to ensure installation quality. Note:YC4D80 engine Oil pressure 0.25-0.6MPa Injection timing 18±2° Valve clearance 0.34-0.36mm At first 250h,check the valve clearance, and every 500h check the valve clearance.

3

YUCHAI Engine Service Manual

12 Marks In order to emphasize the significance of safety and quality visually, and help the user make best use of this manual, we design the signs in table 1-2 as marks. Table 1-2 Marks

Items

Notes Be careful for the safety during the operation.

Safety

Attention

Be quite careful for the safety if there is pressure inside during the operation. Emphasize the technical requirements to ensure that the operation can meet the requirements of standard during operation. Weight and installation way of parts or device.

Weight Carefully select hanging tools and the operation gesture. Tightening torque

Pay more attention to the tightening torque of assembly parts.

Coating

Carefully note the parts need to be coated with grease or adhesion agent.

Oil, water

Fill a certain amount of water, oil and fuel.

Draining

Be careful for the parts where water and oil need to be drained, and judge their volume.

13 Tools and Gauges Table 1-3 Name

Application

Feeler gauge

Used to measure fitting clearance

Pulley damper disassembling tools

Used to disassemble pulley damper

Pulley damper press-in tools

Used to assemble pulley damper

Piston-rod assembly assembling tools

Used to assemble

XB-A rotary type filter wrench

Used to disassemble rotary type engine oil filter

Socket 1-1/8

Used to disassemble damper kingbolts

Socket 1-2

Used to disassemble rear oil seal seat and fuel injection pump gear

Socket 3-8

Used to disassemble cylinder cover shield and gear housing cover plate

Cylinder sleeve disassembling tools

Used to disassemble cylinder sleeve 4

YUCHAI Engine Service Manual

14 Application of YUCHAI Engine Table 1-4 Engine model

Application

YC4108G

LG918

YC4D80-T20

LG920

YC4A105Z-T20

LG926

YC6J125Z

LG933L/LG936L/LG936L (downhole)

YC6J125Z

LG936L/LG936L (downhole)

YC6M220Z-T20

LG953

15 Composition and Significance of YUCHAI Engine Model

YC 4 D 80 – T2 0 Major improvement code Emission standard Power code Series code Number of cyinders Corporate identify Table 1-5 Parameter list of series code Series code

Cylinder bore × stroke (mm)

A

108×132

B

108×125

C

108×120

D

108×115

E

110×112

F

92×100

G

112×132

J

112×132

M

105×125 5

YUCHAI Engine Service Manual

2 Disassembly of Diesel Engine 21 Disassembly of Outer Parts 211 Disassembly

of

Crankcase

Ventilation Device 1.

Take the exhaust breather and its vent pipe out from cylinder cover shield or engine block.

ATTENTION The exhaust breather is usually installed on top of cylinder cover shield, while for some engine models, the breather is installed on engine block side, and different breather has different structure.

1 Fig. 2-1 1 Exhaust breather

212 Disassembly of Fan 1.

Remove the 4 fixing bolts of fan, take the fan assembly down.

ATTENTION Three kinds of fan are equipped on different YUCHAI products, i.e. steel plate fan, engineering plastic fan and silicone oil clutch fan. Fan of different engine model has different mounting position, some are

1

installed on water pump shaft, some are

Fig. 2-2 1 Fixing bolt

installed on independent support and some are installed on crankshaft small end.

6

YUCHAI Engine Service Manual

213 Disassembly of Turbocharger 1.

Disconnect turbocharger oil inlet pipe and oil return pipe, remove the 4 base fastening nuts and the two connecting pipes, take the turbocharger down.

ATTENTION The 4 nuts are special nuts that made of heat-resisting material, which shan’t be lost or wrongly installed. Most turbochargers are installed with bypass valve, and do not touch the adjusting rod in the process of disassembly to prevent affecting engine

Fig. 2-3 1 Turbocharger 2 Bypass valve 3 Oil inlet pipe bolt 4 Oil return pipe weldment 5 Base fastening nut

intake pressure. Be sure not to take the turbocharger actuator as lifting eye to move the turbocharger.

214 Disassembly of Silencer, Exhaust Pipe and Water Outlet Pipe 1.

Remove the fixing bolts of silencer assembly, take down the assembly.

1 2 Fig. 2-4 1 Silencer 3 Exhaust pipe

3 2 Bolt

7

YUCHAI Engine Service Manual 2.

Screw off the fixing bolts of exhaust pipe, take down the pipe and put it aside.

1 Fig. 2-5 1 Bolt

2 2 Exhaust pipe 3.

Remove the connecting bolts between water outlet pipe and cylinder cover, disconnect water outlet pipe from water pump and take down the pipe.

1 Fig. 2-6 1 Water outlet pipe

215 Disassembly of Air Filter 1.

1 Fig. 2-7 1 Fastening nut

8

Screw off the fastening nut of air filter.

YUCHAI Engine Service Manual 2.

Remove the fixing nut of outer filter element, take the filter element out.

1 Fig. 2-8 1 Outer filter element 3.

Remove the fixing nut of inner filter element, take the filter element out.

1 Fig. 2-9 1 Inner filter element 4.

Loosen the connecting clamp between air filter and intake pipe, and remove the connecting bolts. Take the filter down.

1 Fig. 2-10 1 Bolt

2 2 Clamp

9

YUCHAI Engine Service Manual 5.

Remove the connecting bolts between air inlet adapter and intake pipe, take down the adapter.

ATTENTION According to requirements of different engine model, intake pipe is divided into unitary

structure

type

and

split-type

(two-section) structure type (only applies to engine without turbocharger).

2 Fig. 2-11 1 Bolt

2 Air inlet adapter

216 Disassembly of High Pressure Fuel Pipe 1.

Disconnect the connection between each high pressure fuel pipe and injector.

1 Fig. 2-12 1 High pressure fuel pipe joint 2.

Disconnect the connection between each high pressure fuel pipe and injection pump, screw off the fixing bolts of clamp that used to fix intake pipe on engine block. Take down high pressure fuel pipe.

1 2 Fig. 2-13 1 High pressure fuel pipe joint 2 Pipe clamp 10

YUCHAI Engine Service Manual

217 Disassembly of Fuel Coarse Filter 1.

Remove the fixing bolts of fuel pipes that connected to the filter, take down the pipes. Screw off the filter fixing bolts and put the filter aside.

1 2 3 Fig. 2-14 1 Bolt 2 Coarse filter to fuel tank pipe 3 Coarse filter to hand fuel pump pipe

218 Disassembly of Hand Fuel Pump 1.

Remove the fixing bolts of coarse filter to hand fuel pump pipe. Screw off the 3 fixing nuts of hand fuel pump and take the pump down.

1 2 3 Fig. 2-15 1 Breather 2 Nut 3 Hand fuel pump

11

YUCHAI Engine Service Manual

219 Disassembly of Fuel Fine Filter 1.

Remove the fixing bolts of fuel injection pump to fuel fine filter pipe.

1

2

Fig. 2-16 1 Fuel injection pump to fine filter pipe 2 Fuel fine filter 2.

1 Fig. 2-17 1 Fixing nut

12

Remove the fixing nuts of fuel fine filter.

YUCHAI Engine Service Manual

2110 Disassembly

of

Inlet/Return

Pipe

Engine of

Oil Fuel

Injection Pump 1.

Remove the engine oil pipe between injector and fuel injection pump.

1

2

Fig. 2-18 1 Engine oil return pipe

2 Bolt 2.

Remove the engine oil inlet pipe and return pipe of fuel injection pump.

1

2

Fig. 2-19 1 Engine oil inlet pipe of fuel injection pump 1 Engine oil return pipe of fuel injection pump

13

YUCHAI Engine Service Manual

2111 Disassembly of Transmission Belt and Generator Assembly 1.

Loosen the adjusting bolt of generator assembly.

1 2 3 Fig. 2-20 1 Adjusting bolt 2 Generator assembly

3 Fixing bolt 2.

Remove the transmission belt by hand. Screw off the fixing bolts of generator assembly, take the assembly down.

1 Fig. 2-21 1 Transmission belt

14

YUCHAI Engine Service Manual

2112 Disassembly of Fuel Injection Pump Assembly 1.

Remove the connecting bolts between advance device and air compressor.

1 2 3 Fig. 2-22 1 Connecting bolt 2 Connecting flange 3 Fluted connecting plate 4 Advance device

4

2.

Remove the bolts that used to fix fuel injection pump bracket on engine block, take the pump and its bracket down together.

ATTENTION Before disassembling the fuel injection pump, rotate the pump shaft until cylinder 1 is in “fuel supply” state and mark this 1

position to prevent wrong fuel supply

2

timing caused by incorrect reassembling.

Fig. 2-23 1 Fixing bolt 2 Fuel injection pump bracket

15

YUCHAI Engine Service Manual

2113 Disassembly of DC Starter Motor 1.

Remove the connecting bolts between starter motor and flywheel shell, take the starter down.

ATTENTION For some engine models, a pad is installed between starter motor and engine flywheel shell, do not lose it. 1 Fig. 2-24 1 Connecting bolt 2 Starter motor

2

2114 Disassembly of Engine Oil Cooler 1.

Disconnect the oil inlet pipe and outlet pipe from engine oil cooler. Remove the fixing bolts of oil cooler, take the cooler down and put it aside.

1 2 3 4 Fig. 2-25 1 Cooler oil inlet pipe 2 Cooler oil outlet pipe 3 Engine oil cooler 4 Fixing bolt

16

YUCHAI Engine Service Manual

2115 Disassembly

of

Water

Pump

Assembly 1.

Remove the connecting bolts between water pump and engine block, take pump assembly down.

1 Fig. 2-26 1 Water pump assembly

2116 Disassembly of Pulley Damper 1.

Remove the connecting bolts between the pulley and damper.

1 Fig. 2-27 1 Pulley 2.

1

2

Fig. 2-28 1 Damper compression bolt

2 Damper 17

Remove the damper compression bolt.

YUCHAI Engine Service Manual 3.

Push the damper out with two jackscrews. Jackscrew: M12

1 Fig. 2-29 1 Damper

2

2 Jackscrew

18

YUCHAI Engine Service Manual

22 Disassembly of Cylinder Cover Components 221 Disassembly of Cylinder Cover Shield 1.

Loosen the fastening nuts of cylinder cover shield.

ATTENTION In the process of removing cylinder cover shield, please lift the shield up gently to prevent damaging the shield gasket.

1 Fig. 2-30 1 Nut

2 2 Cylinder cover shield

YC6L and YC6112 engine adopt unitary cylinder cover shield (1 shield for 6 cylinders), as shown in Fig. 2-31.

Fig. 2-31 YC6L, YC6112 cylinder cover shield YC6108

and

YC6105

engine

adopt

semi-integral cylinder cover shield (1 shield for 3 cylinders), as shown in Fig. 2-32.

Fig. 2-32 YC6108, YC6105 cylinder cover shield 19

YUCHAI Engine Service Manual YC6M engine adopts independent cylinder cover shield (1 shield for 1 cylinder), as shown in Fig. 2-33. Fig. 2-33 YC6M cylinder cover shield

222 Disassembly

of

Rocker

arm

Assembly 1.

Remove the two lubricating oil (engine oil) pipes.

ATTENTION Lubricating of rocker arm shaft: For YC6105 and YC6108 engine, engine oil pipe on cylinder cover is connected to rocker arm seat for lubricating; For YC6M engine, engine oil flows into rocker arm seat

1 Fig. 2-34 1 Engine oil pipe

through

tappet,

pushrod

and

valve

adjusting screw for lubricating; For other engine models, oil gallery is designed to connect cylinder cover and rocker arm seat for lubricating.

2.

Remove rocker arm shaft fixing nuts. Remove the two rocker arm shafts and take out the pushrods.

1 Fig. 2-35 1 Fixing nut

20

YUCHAI Engine Service Manual

ATTENTION Type of rocker arm shaft: One shaft for one cylinder (for instance, YC6L and YC6M engine)

Fig. 2-36 YC6L engine valve tappet assembly 1 Tappet 2 Pushrod bottom ball 3 Pushrod 4 Pushrod head 5 Rocker arm seat bolt 6 Rocker arm shaft bolt 7 Adjusting bolt 8 Rocker arm 9 Linkage ball 10 Exhaust valve 11 Intake valve

One shaft for all cylinders (YC6112, YC4112, YC4108, YC4110 engine)

Fig. 2-37 YC6112 engine valve mechanism 1 Bolt 2 Rocker arm shaft 3 Exhaust valve 4 Exhaust valve race 5 Valve spring 6 Valve rod oil seal 7 Exhaust valve spring seat 8 Exhaust valve spring teleflex 9 Valve lock clamp

21

YUCHAI Engine Service Manual One shaft for three cylinders (YC6108, YC6105 engine)

Fig. 2-38 YC6108ZLQB valve assembly 1 Big end cover 2 Transmission control valve

tappet

223 Disassembly of Fuel Injector 1.

Remove the fastening nuts of the six fuel injectors. Take the injectors and nuts down.

ATTENTION Copper gaskets should be placed together with corresponding injectors, paste the gaskets with grease to prevent lost, and injectors 1 2 Fig. 2-39 1 Nut

should

be

marked

corresponding cylinder numbers. 2 Fuel injector YC4112 fuel injector assembly

Fig. 2-40 YC4112 fuel injector assembly 1 Injector gasket (used to adjust protrusion) 2 Bolt of fuel return pipe joint

22

with

YUCHAI Engine Service Manual YC6L fuel injector assembly

Fig. 2-41 YC6L fuel injector assembly 1 Injector nut 2 Hemispheric compression gasket 3 High pressure pipe connecting port 4 Fuel return port

224 Disassembly of Valve Lock Clamp, Valve Spring and Valve Valve lock clamp disassembling and assembling tool

1.

Valve Valve spring

Before lifting down the cylinder cover, use valve

lock

clamp

disassembling

and

assembling tool to remove valve lock clamp, valve spring and valve seat. Bind the valve lock clamp groove with rope to prevent valve falling into cylinder sleeve.

Fig. 2-42

ATTENTION When replacing the valve spring, the corresponding cylinder piston should be turned to TDC position to prevent the valve falling into cylinder.

23

YUCHAI Engine Service Manual

225 Disassembly of Cylinder Cover 1.

Take two steps to remove cylinder cover bolts.

1 Fig. 2-43 1 Bolt

ATTENTION Disassembling order of YC6112 cylinder cover bolts.

Fig. 2-43 Disassembling order YC6112 cylinder cover bolts

of

Disassembling order of YC6105 cylinder cover bolts.

Fig. 2-43 Disassembling order YC6105 cylinder cover bolts

of

2.

Install the two middle cylinder cover bolts and lifting eyes. Lift the cylinder cover up slowly, in the meantime knock the four corners of cylinder cover with copper hammer so that it can be detached from engine block easily. Take down cylinder gasket

ATTENTION 1 Fig. 2-46 1 Cylinder cover 3 Locating sleeve

2

Locating sleeves are used to position

3

cylinder cover and engine block, do not lose 2 Cylinder gasket

the locating sleeves.

24

YUCHAI Engine Service Manual

23 Disassembly of Gear Housing and Camshaft 231 Disassembly of Gear Housing 1.

Remove all peripheral fastening bolts and nuts of gear housing, knock the gear housing with copper hammer and take down the gear housing cover plate and gasket.

1 Fig. 2-47 1 Gear housing cover plate

232 Disassembly of Camshaft 1.

Rotate camshaft gear, loosen the two fastening bolts of camshaft thrust plate through the hole on the gear.

Fig. 2-48 1 Woodruff key 2 Spacer bush 3 Camshaft thrust plate 4 Camshaft timing gear 5 Bolt 6 Gasket 7 Bolt

25

YUCHAI Engine Service Manual 2.

Hold camshaft gear with hands, rotate the camshaft and pull it outward slowly to remove it in the meantime.

ATTENTION No big impact is allowed while pulling camshaft out, to avoid damaging camshaft or camshaft hole.

Fig. 2-49 1 Fastening bolt 2 Camshaft thrust plate 3 Camshaft gear 3.

If the camshaft gear needs to be disassembled in the meantime: Remove the gear fixing bolts and gaskets, and then reassemble the fastening bolt and pull the gear out with drawing tools.

ATTENTION The woodruff key on the camshaft mustn’t be damaged or lost. 1 2 Fig. 2-50 1 Fastening bolt

2 Gasket

233 Disassembly of Idle Gear and Idle Gear Shaft ATTENTION If abnormal noise is heard from gear housing before the disassembly, then you should check axial clearance of idle gear first. Refer to 36 Assembly of Gear Housing Cover Plate, Camshaft, Idle Gear Shaft and Gear Housing for details. 26

YUCHAI Engine Service Manual Disassembling method of YC6112, YC4112, YC4110 engine: Only need to remove the fastening bolt of idle gear shaft.

Fig. 2-51 1 Anti-wear plate 2 Idle gear 3 Idle gear sleeve 4 Idle gear shaft 5 Fastening bolt of idle gear shaft

Disassembling method of YC6L, YC6108, YC6105 and YC4108 engine: 1.

Remove the locking plate and fixing bolts of idle gear, take down the pressing plate and idle gear.

1 Fig. 2-52 1 Locking plate 3 Pressing plate

2

3

4 2 Bolt 4 Idle gear

27

YUCHAI Engine Service Manual 2.

1 Fig. 2-53 1 Bolt

Remove the two hexagon bolts.

2 2 Idle gear shaft

234 Disassembly of Air Compressor and Air Compressor Idle Gear 1.

Remove the fixing nut of air compressor idle gear.

1

2

Fig. 2-54 1 Fixing nut 2 Air compressor idle gear 2.

1 Fig. 2-55 1 Air compressor idle gear 28

Take down air compressor idle gear.

YUCHAI Engine Service Manual Disassembling method of YC6108, YC6112, YC6L engine: Air compressor idle gear seat and idle gear are installed on gear housing cover plate. You just need to loosen the idle gear seat bolt and remove the two M6 sunk screws. Fig. 2-56 10 Air compressor idle gear seat 11 Idle gear sleeve 12 Idle gear 13 Anti-wear plate 14 Idle gear bolt 15 Sunk screw

3.

Remove the connecting bolts between air compressor and gear housing, take down the air compressor.

1 Fig. 2-57 1 Bolt

29

YUCHAI Engine Service Manual

24 Disassembly

of

Engine

Oil

Sump, Engine Oil Strainer and Engine Oil Pump 241 Disassembly of Engine Oil Sump ATTENTION Engine oil sump fastening type of YUCHAI products is divided into two kinds: for the first kind, the sump is fastened on engine block with bolts, as shown in Fig. 2-58. 1.

Remove the fastening bolts and take down engine oil sump pressing plate (for YC6112 engine) and the sump.

Fig. 2-58 1 Engine oil pump 3 Safety valve 4 Bolt 6 Filter screen 8 Bolt

2 Bolt 4 Bolt 5 Bolt 7 Oil drain plug 9 Rotor

For the second kind, a bearing seat plate is connected between engine oil sump and engine block (YC6M adopts this structure), as shown in Fig. 2-59. 2.

Loosen the fastening bolts 3 to remove the oil sump. Remove fastening bolts 2, and you can take down bearing seat plate.

ATTENTION Fig. 2-59 1 Crankshaft 2 Fastening bolt 3 Bearing seat plate 4 Pressing block 5 Engine oil sump 6 Fastening bolt 7 Engine block

A magnet is place in oil drain plug on bottom of the sump, do not lose it when cleaning the sump.

30

YUCHAI Engine Service Manual

242 Disassembly

of

Engine

Oil

Strainer 1.

As shown in Fig. 2-60, remove the strainer fastening bolts and strainer support fixing bolts

ATTENTION Strainer support is vulnerable to rupture, please pay attention to check it during normal use.

Fig. 2-60

243 Disassembly of Engine Oil Pump ATTENTION The engine oil pump adopted by YUCHAI products is rotor pump Pump

of

YC4110,

YC4112,

YC6105,

YC6112, YC6M engine is shown in Fig. 2-61.

Fig. 2-61 1 Engine oil pump shaft sleeve 2 Gasket 3 Engine oil pump cover 4 Outer rotor 5 Engine oil pump shaft 6 Safety valve 7 Bolt 8 Safety valve spring 9 Adjusting screw of safety valve spring 10 Bolt 11 Gear 12 Sleeve 13 Inner rotor

31

YUCHAI Engine Service Manual Gear pump of YC6108 and YC6L engine is shown in Fig. 2-62, the pump is installed on front end of engine block.

Fig. 2-62 1 Engine oil pump pressure-limiting valve 2 Pressure-limiting valve spring 3 Engine oil pump driving gear 4 Driving shaft 5 Engine oil pump cover 6 Engine oil pump idle gear 7 Engine oil pump gear 8 Bolt 9 Anti-wear plate 10 Bolt 11 Driven gear shaft 12 Engine oil pump idle gear shaft 13 Locating sleeve YC6105 engine oil pump is installed on the first bearing cap of engine block; YC6M engine oil pump is installed on front end of engine block, small end of crankshaft is taken as engine oil pump shaft, as shown in Fig. 2-63.

Fig. 2-63 1.

Remove the connecting bolts between the first bearing cap of engine block and engine oil pump.

1 2 Fig. 2-64 1 Engine oil pump

2 Bolt 32

YUCHAI Engine Service Manual

25 Disassembly of Flywheel and Flywheel Shell 251 Disassembly of Flywheel 1.

Put the engine on suitable place, remove the connecting bolts between compression plate and flywheel, press the compression plate out with jackscrews and put it aside. Jackscrew: M16

1 2 3 Fig. 2-65 1 Bolt 2 Jackscrew 3 Compression plate 2.

Remove

the

connecting

bolts

between

flywheel and engine block, take down the flywheel and put it aside.

1 Fig. 2-66 1 Forward low gear clutch assembly 3.

Remove

the

connecting

bolts

between

flywheel shell and engine block, take down the shell and oil seals

ATTENTION Do not damage the oil seals.

1 Fig. 2-67 1 Bolt

2 2 Oil seal 33

YUCHAI Engine Service Manual

26 Disassembly

of

Piston

Connecting Rod, Crankshaft and Cylinder Sleeve 261 Disassembly of Piston Connecting Rod REQUIREMENTS (1) The removed piston connecting rod assembly

should

be

marked

with

cylinder number and placed orderly. (2) Connecting rod bolts, connecting rod cap and connecting rod bearing shells should be assembled together in their original way. (3) To

prevent

damaging

thread

of

connecting rod bolts, please don’t screw off the bolts with pneumatic impact wrench.

1.

Place

the

engine

upside

down.

Rotate

crankshaft until the to-be removed piston connecting rod assembly reaches BDC (bottom dead center), remove connecting rod bolts with torque spanner and socket crosswise and stepwise, take down the connecting rod cap.

12 Fig. 2-68 1 Connecting rod bolt 2 Connecting rod cap

34

YUCHAI Engine Service Manual 2.

Hold up the big end of connecting rod with soft metal (such as copper and aluminum) plate or clean wood board and then push piston connecting rod assembly out with soft metal bar or wood hammer.

ATTENTION Be careful not to bump or scratch the crankshaft journal, connecting rod journal

1 2 Fig. 2-69 1 Connecting rod assembly 2 Piston

and

cylinder

sleeve

hole

during

the

operation.

ATTENTION For YC6L and YC4110 engine, clearance fit is adopted between cylinder sleeve and engine block. When disassembling piston connecting rod assembly, you must fasten a cylinder bolt on engine block with a piston pin or compression plate between them to

Fig. 2-70

block the cylinder sleeve, only in this way can the piston connecting rod assembly be pushed out.

262 Disassembly of Crankshaft REQUIREMENTS (1) In the process of failure predication, if you suspect that the poor fit failure between bearing shell and bearing journal may be caused by insufficient torque of bearing cap fastening bolts, then before the disassembly, you should check whether fastening torque of each bolt is in required range, and use it as a 35

YUCHAI Engine Service Manual basis for fault analysis. (2) Clearance

fit

is

adopted

between

bearing cap and bearing seat for YC4108, YC6105, YC6108 engine, two locating sleeves in bolt holes on bearing cap are used for positioning. While for other engine models, interference fit is adopted, and positioning is ensured by machining of engine block bearing seat, so when disassembling bearing cap, you may encounter some difficulty, please proceed with caution, as shown in Fig. 2-71. For YC6L engine, a threaded hole Fig. 2-71

is processed in the middle of bearing cap, which is used for lifting. For YC6M engine, all bearing caps are designed as a whole (unitary structure), two locating pins on two ends are used for positioning. (3) The removed bearing shells should be placed

together

with

their

corresponding bearing caps to prevent confusion. 1.

Take two steps to loosen bearing cap fastening bolts with torque wrench according to the order marked in Fig. 2-72, take down the caps respectively.

Fig. 2-72

36

YUCHAI Engine Service Manual 2.

Lift the crankshaft out slowly and put it on clean support.

1 Fig. 2-73 1 Crankshaft

263 Disassembly of Cylinder Sleeve ATTENTION (1) Cylinder sleeve of YUCHAI products is divided into wet type and dry type, YC6105, YC6108, YC4108, YC6L and YC6M engine adopt wet-type cylinder sleeves, clearance fit is adopted between cylinder sleeve and engine block, you just need to push the sleeve from lower end with soft metal bar or wood bar to remove it.

(2) YC4112 and YC4110 engine applies

Dry-type cylinder sleeve disassembling tool

dry-type cylinder sleeves. For YC4112, Cylinder block

interference fit is adopted; while for YC4110, clearance fit is adopted. When Dry-type cylinder sleeve

disassembling

cylinder

sleeves

of

YC4112 engine, special cylinder sleeve Disassembling accessory

disassembling tool is needed, as shown in Fig. 2-74.

Fig. 2-74

37

YUCHAI Engine Service Manual (3) YC6112 is cylinder sleeve-free engine, whose piston directly fits with cylinder hole. engine

Exceptionally, is

equipped

some

YC6112

with

dry-type

cylinder sleeve (applies bottom-dead structure), as shown in Fig. 2-75. Special cylinder sleeve disassembling tool is also needed to disassemble the cylinder sleeves. Tips: if no cylinder sleeve disassembling tool is available, you can put the engine block on boring machine and bore the to-be replaced cylinder sleeve to remove it. But be careful not to damage the bottom-dead shoulder.

Fig. 2-75

38

YUCHAI Engine Service Manual

3 Assembly of Diesel Engine 31 Selection of Cleaning Fluid Before reassembling the engine, all removed parts must be cleaned carefully, including cleaning part surface, oil dirt in inner cavity, carbon deposit, water scale and rust.

311 Cleaning of Oil Dirt Generally, volatile solvent is used to dissolve and clear away oil dirt on pats, such as gasoline, diesel oil and kerosene. These solvents are easy to buy and convenient to use, no damage to the parts and cleaning effect is good, but their cost is high, what’s more, volatile solvent can easily lead to fire hazard. Thus, these solvents are usually used to clean precision parts with high cleaning requirements. Another cleaning fluid that used to clean oil dirt is alkaline solution (prepared with alkali or alkalic salt), which is mainly used to clear away oil dirt on steel/iron parts. Formula of commonly used alkaline solution is listed in table 3-1. Because strong alkalinity is highly corrosive to nonferrous metals, when cleaning nonferrous metal parts, use the alkaline solution listed in table 3-2. Table 3-1 Formula of alkaline solution for cleaning of oil dirt on steel/iron parts Formula Category

Caustic soda (g)

Sodium carbonate (g)

Sodium silicate (g)

A

7.5

50

10

B

20

50

Liquid soap (g)

Trisodium phosphate (g)

Water (g)

1.5

1000

30

1000

Table 3-2 Formula of alkaline solution for cleaning of oil dirt on nonferrous metal parts Formula Category

Sodium carbonate (g)

A

10

B

4

Sodium silicate (g)

1.5

Sodium dichromate (g)

Water (g)

0.5

1000

30

1000

When cleaning the parts with alkaline solution, you should heat the solution to 80~90oC in advance. After all oil dirt is cleared away, wash the parts with hot water to get rid of the residual alkaline solution to prevent corroding the parts, and dry them with compressed air at last. We recommend you to use GF-III metal cleaning fluid for normal circumstances, which is convenient, safe and effective. 39

YUCHAI Engine Service Manual

ATTENTION The chemicals listed in the tables above are corrosive, please operate with great caution and take protective measures.

312 Removal of Carbon Deposit Carbon deposit is poor combustion product and combustion product of bursting engine oil, mainly appears on parts around combustion chamber. Harm to the machine caused by carbon deposit: Inflexible movement, larger resistance and power reduction. If there is too much carbon deposit on part surface, radiating performance will be greatly affected, overheating will occur. Too much carbon deposit on piston and piston ring will result in scuffing of cylinder bore. Too much carbon deposit in fuel injector will block the injector, and engine will not work normally. Thus, when maintaining the engine, you should pay serious attention to carbon deposit problem. Tools to remove carbon deposit: scraping knife, perching knife and wire brush. Fig. 3-1 represents removal of valve carbon deposit, Fig. 3-2 represents removal of piston top carbon deposit. This method is simple and practicable, but the removal isn’t clear enough, and easy to leave scratch on part surface.

Fig. 3-1 Removal of valve carbon deposit

Fig. 3-2 Removal of piston top carbon deposit

Another method to remove carbon deposit is to use decarbonizer. The way to do this is: keep the part (with carbon deposit) immersed in decarbonizer (80~90oC) for 2~3h, after the carbon deposit gets soft, wipe it off with brush or cleaning cloth, wash the part with hot water and dry it with compressed air at last. Formula of decarbonizer for removal of carbon deposit on steel/iron parts and aluminum alloy parts is list in table 3-3 and 3-4.

40

YUCHAI Engine Service Manual Table 3-3 Formula of decarbonizer for removal of carbon deposit on steel/iron parts Sodium Formula Caustic soda carbonate Category (g) (g) A

25

B

100

C

25

Sodium Sodium Liquid soap dichromate silicate (g) (g) (g)

Water (g)

1.5

1000

31

8.5

5 31

1000

5

10

5

1000

Table 3-4 Formula of decarbonizer for removal of carbon deposit on aluminum alloy parts Formula Sodium Sodium Sodium silicate Liquid soap (g) Category carbonate (g) dichromate (g) (g) A

18.5

B

20

5

C

10

5

Water (g)

18.5

10

1000

8

10

1000

10

1000

313 Removal of Water Scale A layer of yellowish-white water scale will be deposited on inner wall of cylinder cover cooling water jacket and radiator after long-time using cooling water (not coolant). Water scale can block circulating water channel and result in engine overheating. If hard water is used in the engine, the water scale problem could get even worse. Formula of descaling agent is listed in Fig. 3-5. Prepare the descaling agent (A/B) according to the formula listed in Fig. 3-5 and filter it, fill enough descaling agent into engine cooling system and let it stand for 10~12h, and then start the engine, increase the engine speed to a little higher than idle speed and run it for 10~15min to heat the descaling agent to 80oC or higher and then stop the engine. After the temperature drops to 60oC or lower, start the engine again and run it idly for 2min, and then stop the engine, drain the descaling agent out. Then fill clean water and start the engine to clean engine cooling system. Table 3-5 Formula of descaling agent Formula Sodium carbonate Hydrous sodium Category (g) carbonate (g) A B

10 100

Kerosene (g)

Water (g)

15

1000

50

1000

Advantages of this method are: efficient, less corrosive to copper and welded joint, but you should 41

YUCHAI Engine Service Manual note that harmful gas will be generated when acid solution reacting with water scale, protective measures shall be taken.

314 Removal of Rust Steel/iron parts can be easily rusted by water and oxygen in the air, rust will directly affect surface quality of the parts and must be thoroughly removed. Common tools to remove rust: steel wire, scraping knife, perching knife and abrasive cloth. Be careful not to damage the finished surface of the part.

42

YUCHAI Engine Service Manual

32 Assembly of Engine Block 321 Cleaning of Engine Block Before the cleaning, you should preliminarily check the engine block and ensure it is in good condition for use. Check the engine block for casting flaws like crack and sand hole, check whether machining processes is complete, check the finished surfaces for bumping damage. 1.

Remove the peripheral dirt on engine block with high pressure water, and then clear away the oil dirt, burnt-on sand and carbon deposit and sediment on inner and outer surface of engine block, oil gallery and water channel with cleaning agent.

Fig. 3-3 2.

Clean each oil gallery (especially main oil gallery and auxiliary oil gallery, this two oil galleries must be cleaned with clean cloth pieces), inner cavity, main bearing holes, camshaft bearing holes, main bearing bolt holes and cylinder cover bolt holes, and dry them with compressed air. Inspection and qualification of engine block cleanliness:

Fig. 3-4

The white cloth shouldn’t turn black after getting through oil gallery, check each oil gallery and inner cavity with strong magnetic rod, which should be free of iron particle.

43

YUCHAI Engine Service Manual 3.

If there is too much deposited water scale in water channel and water cavity, descaling agent should be used to remove it. No iron particle and debris is allowed in each shaft hole and bolt hole, carbon deposit and sealant should be removed with perching knife. Dry engine block with compressed air at last.

Fig. 3-5

322 Inspection of Engine Block 1.

Measure main bearing seat bore diameter: As shown in Fig. 3-6, assemble main bearing cap on engine block and tighten the bolts to required torque. Calibrate the bore dial indicator (division value 0.01mm) and use it to measure diameter of main bearing seat bore working section in x and y direction, group the measured results according to table 3-6.

Fig. 3-6 Measuring of main bearing seat bore diameter Table 3-6 Main bearing seat bore diameter grouping table for each engine model (mm) Group

2.

Engine model YC6112, YC4112, YC 6105, YC6108, YC4110 YC4108

YC6113

A (Φ)

92.055~92.065

91~91.018

92~92.018

B (Φ)

92.065~92.075

91.018~91.035

92.018~92.035

YC6M

10~108.022

Method to measure diameter of main bearing hole (with bearing shells): Refer to Fig. 3-6. Install the corresponding main bearing shells on each main bearing seat and bearing cap according to grouping condition of main bearing seat bore diameter, and then measure the diameter of main bearing hole according to the method exposed in 1, the measured results 44

YUCHAI Engine Service Manual should meet the requirements listed in table 3-7. Table 3-7 Standard diameter of main bearing hole (with bearing shells) for each engine model (mm) Engine model

YC6112, YC4112, YC4110

YC6105

YC4108

YC6108

YC6M

YC6108ZLB

Diameter 85.721~85.765 85.06~85.105 85.06~85.122 85.05~85.115 108~108.022 87.05~85.115 (Φ) 3.

For the convenience of calculating circular degree and cylindricity deviation of cylinder sleeve hole, when measuring cylinder sleeve bore diameter, measure it in the vertical direction of the highest point and lowest point of the second piston ring, as shown in Fig. 3-7, the measured value should be in the range listed in table 3-8, otherwise, the sleeve should be replaced. For cylinder sleeve-free engine (YC6112 engine), replace the engine block, bore the cylinder hole or add a cylinder sleeve to solve the out-of-tolerance problem.

4.

Measure the protrusion of cylinder sleeve (to engine block top surface), as shown in Fig. 3-8 and Fig. 3-9. Cylinder sleeve of YC4110 engine is free of waterproof ring, while that of other engine models is designed with waterproof ring.

Fig. 3-7 Measuring of cylinder sleeve bore diameter

Fig. 3-8 Measuring of cylinder sleeve protrusion

Table 3-8 Specified value of cylinder sleeve bore diameter, circular degree, cylindricity deviation and protrusion for each cylinder model (mm) Cylinder sleeve Item bore diameter

Cylinder sleeve circular degree

Cylinder sleeve cylindricity deviation

Cylinder sleeve protrusion

Specified value

Specified value

Specified value

Specified value

YC6112

111.778~111.816

0.01

0.01

0.02~0.09

YC4112

111.778~111.816

0.01

0.01

0~0.08

YC6105

105~105.022

0.01

0.01

0.07~0.11

YC6108

108~108.035

0.01

0.01

0.02~0.08

Engine model

45

YUCHAI Engine Service Manual YC4108

108~108.022

0.01

0.01

0.04~0.08

YC4110

110~110.035

0.015

0.015

0~0.08

YC6L

113~113.022

0.01

YC6M

120~120.022

0.01

0.105~0.155 0.01

0.02~0.08

Cylinder sleeve protrusion

Pay attention to clear away carbon deposit and burr on this surface when replacing the sleeve Engine block Cylinder sleeve

Fig. 3-9 Measuring of cylinder sleeve protrusion

ATTENTION Adjusting of cylinder sleeve protrusion can be done by switching the cylinder sleeves, protrusion difference of two adjacent cylinder sleeves should not exceed 0.04mm. 5.

Removed main bearing caps should be assembled to their original position, do not interchange them, side face of each engine block is casted with casting number, and bottom surface is printed with processing number, engine number is printed on side face of engine block too; each bearing cap is printed with processing number, installation number and installing direction (arrow) on the bottom. Refer to Fig. 3-10 and Fig. 3-11. Bearing cap Processing number Casting number

Engine number

Fig. 3-10 YC6105 engine block 6.

Bearing shell locating grooves 4 are processed on fitting surfaces of bearing seat and bearing cap, the two grooves should be on the same side after assembling. As shown in Fig 3-11.

46

YUCHAI Engine Service Manual

1 Cylinder number A/B mark

2 Installing direction (arrow) 3 Processing number 4 Bearing shell locating grooves 5 Threaded hole (should be clean and free of dirt) 6 No burr on the edge 7 Oil hole A- Represents matching with red shell B- A-Represents matching with blue shell

Fig. 3-11 Main bearing cap 7.

C-

Measuring of camshaft sleeve bore diameter Refer to Fig. 3-6 for measuring method. Specified camshaft sleeve bore diameter and fitting clearance between camshaft and camshaft sleeve for each engine model are listed in table 3-9

Table 3-9 Specified camshaft sleeve bore diameter and fitting clearance between camshaft and camshaft sleeve for each engine model (mm) YC6108Z YC6105 Engine model YC6112 QB 6108ZQ YC4108 YC4110 Value YC4112 YC6108Z 6108ZQN LQB Specified camshaft 60.744~ 55.5~ 60.0~ 58.5~ 60.744~ sleeve bore diameter (Φ) 60.769 55.53 60.03 58.53 60.770 0.0762~ 0.06~ 0.06~ 0.03~ 0.076~ Fitting clearance 0.127 0.109 0.109 0.09 0.128 Fitting limit reference 0.152 0.25 0.25 0.25 0.152 value

YC6L

YC6M

60.0~ 60.03 0.06~ 0.109

60.01~ 60.06 0.04~ 0.12

0.25

0.25

ATTENTION If the measured value is not in the specified range listed in table 3-9, then the sleeve should be replaced.

47

YUCHAI Engine Service Manual

323 Assembly of Engine Block Parts that installed on engine block are numerous, only parts with special assembling requirements are listed below.

Fig. 3-12 YC6108 cylinder block assembly (1) 1 Bearing cap

2 Cylinder block

3 Main bearing bolt

4 Locating sleeve

5 Timing idle gear

6 Idle gear bearing

7 Idle gear bearing

8 Idle gear shaft sleeve

9 Idle gear baffle

10 Locking plate

11 Small bolt

14 Water seal ring

15 Cylinder sleeve

18 Engine oil pump intermediate drive gear

19 Bearing

27 Cylinder gasket

29 Breather

34 Adjusting gasket

37 Sphere gasket

40 Bracket bolt 44 Main oil gallery sealing plug

33 Engine oil pump bracket

48

YUCHAI Engine Service Manual

Fig. 3-13 YC6108 cylinder block assembly (2) 1 Camshaft sleeve

2 Intermediate main bearing cap

3 Main bearing cap

4 Main bearing bolt

5 Pin

15 Low oil pressure alarm

8 Camshaft end cover bolt

18 Pressure regulating valve assembly

1.

20 Oil pressure alarm

Installation of water block and main gallery oil block

Refer to Fig. 3-14 for installing of water block, installation requirements: sealing surface of water block should be applied with 11747 sealant; after assembling, outer end face of water block should be level with or lower than engine block.

Fig. 3-14 Installation of engine water block Installation of main gallery oil block: Main gallery oil block includes front oil block and rear oil block, front oil block of YC4110, YC4112 and YC6112 engine is bowl-shape plug, while rear oil block is hexagonal socket head plug. 49

YUCHAI Engine Service Manual Front oil block of YC4108, YC6105, YC6108, YC6L and YC6M engine is sealing plug (with O-ring), while rear oil block is bowl-shape plug, as shown in Fig. 3-15. Hexagonal socket head plug O-ring Sealing plug Bowl-shape plug

Fig. 3-15 Main gallery oil block

INSTALLATION REQUIREMENTS: (1) Middle section of plug screw should be applied with 545 sealant and tightened with socket head wrench. (2) Add an O-ring to install the sealing plug, be careful not to damage the O-ring. (3) After assembling, outer end face of plug or sealing plug should be a little lower than engine block end face. (4) 2.

When assembling, knock-in with soft metal.

Precautions for installation of camshaft sleeve. Refer to Fig. 3-16. Camshaft sleeve

Rear end chamfer

Rear end of engine block

Fig. 3-16 Installation of camshaft sleeve (1) Only rear end of camshaft hole is processed with chamfer, so when installing the sleeve, insert it from the rear end of engine block, as shown in Fig. 3-16. (2) Oil hole on the sleeve must be aligned to oil inlet hole on engine block. ATTENTION: Not every camshaft sleeve is designed with oil hole, for YC6105 and YC6108 engine, the third 50

YUCHAI Engine Service Manual and sixth (cylinder number) sleeves are designed with one oil hole respectively that connected to rocker arm seat; for YC6M engine, only one oil hole needs to be aligned (because there is oil groove processed on bearing shell); for YC4108 engine, the second and fourth (cylinder number) sleeves are designed with one oil hole respectively that connected to rocker arm seat; for other engine models, only the first (cylinder number) sleeve is designed with one oil hole that connected to rocker arm seat. You should pay special attention to this when assembling. (3) After the installation, horizontal boring machine should be used to process the sleeve to specified dimension (refer to table 3-9). 3.

Precautions for installation of cylinder sleeve. (1) Rust and carbon deposit on cylinder sleeve shoulder must be cleared away. (2) Check whether the cylinder sleeve bore diameter meets the requirements listed in table 3-8 before installing. (3) Install waterproof ring on cylinder sleeve (YC6112 (with cylinder sleeve), YC4112 and YC4110 engine apply dry-type cylinder sleeve, no waterproof ring is needed), as shown in Fig. 3-17. (4) When assembling the cylinder sleeve to engine block, you should apply some engine oil on the waterproof ring first, rotate the sleeve while press it in the meantime. If fail to press it in by hand, place a wood board on the sleeve and knock it in place, as shown in Fig. 3-18. Interference fit is adopted between cylinder sleeve and engine block for YC4112 and YC4112 engine, so the sleeve should be cooled in liquid nitrogen for 10min before assembling. Clearance fit is adopted for YC4110 engine. (5) After the installation, cylinder sleeve protrusion should be measured according to the method exposed in Fig. 3-8. For YC6L engine, the protrusion can be adjusted by adding or reducing number of adjusting gaskets (chamfer side upward). When matching cylinder sleeves, the color of selected cylinder sleeve should be the same as engine block grouping color, i.e. red to red, blue to blue (or A to A, B to B).We won't elaborate here.

TIPS In principle, grouping assembling is applied between fitting of cylinder sleeve and engine block.

51

YUCHAI Engine Service Manual

Fig. 3-17 Installation of waterproof ring 1 Waterproof ring 4.

2 Cylinder sleeve

Fig. 3-18 Installation of cylinder sleeve 3 Adjusting gasket

Installation of engine oil cooled nozzle and hook. Refer to Fig. 3-19 and Fig. 3-20.

Installation method of engine oil cooled nozzle/hook and precautions (1) Nozzle material is oil-resisting high-temperature engineering plastic, when installing, you just need to press it into the fitting hole on main bearing seat. The nozzle should be pressed in place and no protrusion to the fitting hole. After the installation, fill diesel oil with grease gun to perform injection test: when the piston gets to TDC, the fuel spray must be injected on cylinder inner wall, and the fuel spay mustn’t be forked.

ATTENTION When disassembling the oil sump of a long-time used engine, you should pay attention to check whether the nozzles are aged and damaged, replace if necessary. (2) Engine oil cooled hook is steel tube weldment, and positioned by locating pin when assembling, fastened on engine block with bolts. Before assembling, you should check whether pressure-limiting valve ball is flexible, whether oil hole on the weldment is unblocked. For engine that requires fuel must be injected into engine oil cooled gallery on piston (ensured by machining precision of the weldment), this should be checked. And no interference is allowed between the hook and piston skirt or crankshaft counterbalance

ATTENTION The piston for assembling must be processed with hook back-off opening. Refer to Fig. 3-19.

52

YUCHAI Engine Service Manual Applicable to YC6112, YC4110 and YC4108 engine

Applicable to YC4112, YC6105, YC6108, YC6L and YC6120 engine Fastening bolt Pressure spring Nozzle Hook

Ball valve

Locating pin Hook

Piston engine oil cooled nozzle Fig. 3-19 Installation of engine oil cooled nozzle

Fig. 3-20 Installation of engine oil cooled hook

324 Elimination of Engine Block Common Faults 1.

If there is sand hole or crack on engine block and the sand hole or crack is not on main oil gallery, water channel or engine block stress surface, the sand hole or crack can be fixed by welding with cast iron electrode or inlaying with aluminum strip after being enlarged. As shown in Fig. 3-21. Welding repair

Crack

Sand hole Engine block

Fig. 3-21 Repair of engine block 2.

Fig. 3-22 Shape of cylinder bore shoulder

Main bearing cap damage. Replace the bearing cap, in principle, you can only use half-finished bearing cap (fasten it on the matching cylinder to specified torque and then bore it to specified dimension listed in table 3-6. If boring the bearing cap is not available, you can choose a suitable old bearing cap and fit by grinding the bearing shells (the requirements are: ensure crankshaft can rotate flexibly and no engine oil pressure reduction is caused).

3.

Fit camshaft sleeve The method to fit camshaft sleeve is boring and reaming, which has been exposed previously. 53

YUCHAI Engine Service Manual Here we introduce how to fit when a sleeve is damaged and replaced: press the new sleeve into the fitting hole according to the method previously exposed, clear away the blur on sleeve, wipe out the camshaft and fit it into the sleeve and check the flexibility. It is qualified if the camshaft can rotate flexibly. If the camshaft cannot rotate flexibly (the fitting is too tight), then coat the sleeves with red lead powder, reassemble and check the flexibility again, bore or ream to fit. Camshaft sleeve fitting hole of YC6108 and YC6105 engine applies open structure and can use a scraping knife to fit; while fitting hole of other engine models apply closed structure, only fit by sanding with waterproof abrasive paper and polishing. 4.

After assembling cylinder sleeve, if the protrusion exceeds specified value listed in table 3-8, then you can interchange the sleeves to meet the requirements, never process the engine block step surface to prevent damaging the reasonable fitting condition. As shown in Fig. 3-22.

ATTENTION Clear away the blur and carbon deposit on the step surface, contact area should be more than 80%. Poor fitting and large protrusion are the main causes for breakage of cylinder sleeve journal. 5.

Abrasion of cylinder sleeve: if abnormal premature wear is happened to the cylinder sleeve, you should find out the cause as soon as possible: (1) Check engine oil quality and check whether cooling and ejecting of engine oil is normal; (2) Improperly maintained air filter or short circuit; (3) Long-term low-temperature (66oC or under) low-speed running; (4) Disqualified cylinder sleeve material (in this case, abrasion of piston and piston ring is not serious).

6.

Cavitation of cylinder sleeve: common cylinder sleeve cavitation is partial, main causes are: cylinder sleeve is too close to cylinder wall, poor circulating of cooling water leading to overheating, bubbles come out from high temperature water, explode and continuously impact cylinder sleeve outer wall under the vibration of cylinder sleeve. Handling method: properly grind or polish engine block failure area (protruding area), but without affecting cylinder block strength.

TIPS For the planeness problem of engine block upper surface, so far, we didn’t find any engine failure caused by oversize planeness error, so please do not casually polish this surface to prevent affecting plane quality of the engine block. 7.

Inlay-fit cylinder sleeve: only for YC6112 engine. As shown in Fig. 3-23.

54

YUCHAI Engine Service Manual 0.8×45

Knurling depth of surface A: 0.008~0.012mm Cross angle: 30~60° Area: 50%~70%

Half-finished cylinder sleeve Cylinder sleeve fitting hole

Inlay-fit cylinder sleeve

Fig. 3-23 Inlay-fit YC6112 cylinder sleeve

55

YUCHAI Engine Service Manual

33 Assembly of Crankshaft 331 Cleaning of Crankshaft Crankshafts of YUCHAI products have basically the same structure, only the accessories on front and rear ends are different, here we take YC6108 for example to describe. As shown in Fig. 3-24.

Colored position

Fig. 3-24 YC6108 crankshaft and flywheel assembly 1 Bolt

2 A/C pulley

3 Pulley

4 Silicone oil damper

6 Thrust plate

7 Bearing gasket

9 Flywheel bolt

10 Locating pin

1.

5 Crankshaft timing gear 8 Bearing

Clear away oil dirt and anti-rust oil on crankshaft with kerosene. Wash crankshaft external surface and all threaded holes with soft hairbrush. Rust on the journal should be rubbed with 120-mesh fine sandpaper and polished with sand belt.

2.

Spray-wash the oil galleries and oil holes with metal antirust cleaner repeatedly, and poke-wash them with clean cloth strips to ensure the oil gallery unblocked.

3.

Check the oil galleries and oil holes with strong magnetic rod, if there are iron particles, clean it again according to step 2.

4.

Finally, rinse the crankshaft with clean water to remove residual cleaner and dry the galleries and holes with compressed air, apply suitable engine oil on crankshaft finished surface for protection timely.

332 Inspection of Crankshaft Inspection items are: main journal diameter, diameter of crankshaft connecting rod journal, journal 56

YUCHAI Engine Service Manual roughness, thrust surface roughness, dynamic unbalance value, distance between center lines of main journal and crankshaft connecting rod journal, and crankshaft run-out, etc. 1.

Measure main journal diameter and diameter of crankshaft connecting rod journal, calculate the cylindricity error. Refer to table 3-10 and Fig. 3-25.

Fig. 3-25 Measuring of main journal diameter and crankshaft connecting rod journal diameter Table 3-10 Required diameter value and cylindricity error of main journal and crankshaft connecting rod journal for each engine model. (mm) YC YC411 YC610 YC Engine 6112, 0 5 6108 model YC Item 4112 Main journal (Φ) Crankshaft connecting rod journal (Φ) Main journal cylindricity error Crankshaft connecting rod journal cylindricity error 2.

85.631~85.656 69.84~69.86

YC 4108

YC 6113

84.965~85

YC 6M

YC611 2, YC 4112

86.965 ~87

99.978 ~100

65.97 ~66

69.97 ~70

69.978 ~70

65.97 ~66

79.97 ~80

81.978 ~82

0.0664

0.005

0.006

0.01

0.006

0.01

0.005

0.006

0.0664

0.005

0.005

0.008

0.005

0.008

0.005

0.006

Inspection of surface roughness

Main check points are: surface of main journal and crankshaft connecting rod journal, connecting rod journal shoulder, round corner of main journal and crankshaft connecting rod journal, finished surface of front and rear ends. Inspection method: a. Compare to sample plate by visual, main journal and crankshaft connecting rod journal should be free of scratch, the round corner should be 100% polished and the transitional area should be smooth. b. Measure with roughness detector. 3.

Measuring of dynamic unbalance value. Every crankshaft has passed tests regarding dynamic unbalance value before delivery, so you don’t have to perform this inspection under normal circumstance, but if the engine vibrates excessively during normal use, this inspection must be 57

YUCHAI Engine Service Manual done. Measuring of dynamic unbalance value should be performed on a dynamic balancer, crankshaft dynamic unbalance value for each engine model is listed in table 3-11. If the crankshaft need to be weight-reduced, you can drill holes on circumference surface of balancing block to remove the material, it is required that the hole diameter should be less than 15mm, depth should be less than 30mm and hole edge space should be greater than 5mm. Table 3-11 Crankshaft dynamic unbalance value for each engine model Engine model YC6112 YC4112 YC6105 YC6108 YC4108 YC4110

YC6L

YC6M

≤50

≤40

Item Crankshaft dynamic unbalance value (g•cm) 4.

≤36

≤20

≤50

≤50

≤20

≤20

Measure crankshaft bending error, refer to Fig. 3-26.

Fig. 3-26 Measuring of crankshaft bending error Measure the bending error between main journal on two ends and the fourth main journal, the error value should be in the range listed in table 3-12. Table 3-12 Crankshaft bending error value Engine 6-cylinder engine Value

4-cylinder engine

Specified value

≤0.05

＜0.04

Limit value

＜0.15

＜0.13

5.

Measure crank radius

If no special gauge is available, measure according to the method exposed in Fig. 3-26, half of the measured value difference when the connecting rod journal in the lowest point and highest point is crank radius, which should be in the range specified in table 3-13.

58

YUCHAI Engine Service Manual Table 3-13 Crank radius YC6112 Engine YC4108Z YC6108ZQB YC6105 model LQ YC6108ZQLB YC6108 Value YC4112 Crank radius

66.04±0.05

66±0.05

YC4108 YC4110 YC6L

YC6M

62.5±0.05 57.5±0.05 56±0.05 70±0.06 72.5±0.06

333 Assembly of Crankshaft 1.

Assembly of crankshaft gear:

Interference fit is adopted between crankshaft timing gear and crankshaft small end, you should heat the gear with electromagnetic induction heater (or other way) to about 120oC when assembling, install the heated gear on crankshaft small end immediately based on its locating requirements (crankshaft of different engine model has different locating requirement, pin locating: YC6105ZLQ, YC6108ZLQB and YC6L; key locating: YC4110, YC4112, YC6105QC and YC6108QC; fixture locating: YC6112), ensure the gear is properly fitted with crankshaft shoulder. As shown in Fig. 3-27.

Heat to 120oC

Fig. 3-27

TIPS The timing gear is assembled on crankshaft by the manufacturer before delivery, and without dedicated tools, the gear is difficult to be disassembled. So when replacing the parts, the gear and crankshaft should be replaced together. Tips: some crankshaft timing gears that delivered in the second half of 2003 are free of locating pin or key, if valve timing of engine equipped with this kind of crankshaft gear is changed, check if the gear is loose first. 2.

Installation of crankshaft rear end bearing and bearing sleeve. For YC4110 engine, only bearing 59

YUCHAI Engine Service Manual sleeve needs to be installed; for YC4108, YC6105, YC6108 and YC6L engine, firstly install the sleeve and then install the 6205-Z bearing; while for YC4112, YC6112 and YC6M engine, the bearing is installed on flywheel. Refer to Fig. 3-28 and Fig. 3-29.

Fig. 3-28 Installation of crankshaft bearing

Bearing Sleeve

Fig. 3-29 Crankshaft bearing and bearing sleeve

TIPS Crankshaft bearing and bearing sleeve should be assembled in place (no clearance to the stop shoulder). For crankshaft bearing, the side with end cover should face outward, and fully-enclosed bearing is free of lubricating oil. As engine model varies greatly, assembling requirements of crankshaft bearing and bearing sleeve were chosen according to transmission box type, please recover them without change after maintenance. 3.

Steps to lift and assemble crankshaft and precautions (1) Install main bearing shells: when assembling a new engine, color mark on the bearing shell should be the same as that on main journal. This is not mandatory in normal maintenance, but you must ensure the fitting clearance is specified range. Bearing shell locating grooves are processed on fitting surfaces of bearing seat and bearing cap, the bearing shell lip should be aligned to the grooves after assembling. In the meantime, oil hole on bearing 60

YUCHAI Engine Service Manual shell should be aligned to that on bearing seat too, refer to Fig. 3-11 (for YC6L engine, because there is oil groove processed on bearing seat, no oil hole needs to be aligned when assembling. As shown in Fig. 3-30) Oil groove Oil inlet hole Locating groove Upper bearing seat

Fig. 3-30 YC6L engine bearing seat (2) Apply suitable engine oil bearing seat oil holes and bearing shells. (3) Lift and install crankshaft: place the crankshaft slowly and correctly, apply suitable engine oil on main journal and journal oil holes, rotate the crankshaft and make sure it is flexible. After placed the crankshaft, install the thrust plates. For YC6105 and YC6108 engine, the thrust plates should be installed on the fourth bearing seat; For YC4108 engine, the thrust plates should be installed on the third bearing seat; For YC6M engine, the thrust plates should be installed on the second bearing seat. Other engines apply thrust shoes, for YC6L engine, the bearing shoes should be installed on the fourth bearing seat; for YC4110 and YC4112 engine, the bearing shoes should be installed on the third bearing seat; for YC6112 engine, the bearing shoes should be installed on the fifth bearing seat. Correct installation of thrust plate: as shown in Fig. 3-31.

61

YUCHAI Engine Service Manual Thrust plate Upper bearing seat

Locating lug Crankshaft Thrust plate groove

Lower thrust plate Axial clearance

Crankshaft

Fig. 3-31 Installation of thrust plate (4) Install lower bearing shells. Similarly, when assembling a new engine, color mark on the bearing shell should be the same as that on journal. In the meantime, install the lower thrust plates on upper bearing caps. Apply suitable engine oil on the shells. (5) Refer to Fig. 3-10 to assemble the main bearing caps, knock them in place with copper hammer. Apply suitable engine oil on thread of bearing cap bolts and screw-in the bolts by hand for a few circles. Take three steps to tighten the bolts from the middle to both ends orderly. As shown in Fig. 3-32.

ATTENTION After each tightening step, you should rotate the crankshaft by hand and ensure it is flexible, otherwise, find out the cause and solve the problem. Tightening torque of main bearing cap bolts for each engine model is listed in table 3-14. Table 3-14 Tightening torque of main bearing cap bolts for each engine model Engine model

YC4108

YC4110

YC4112

YC6105

YC6108

YC6112

YC6L

YC6M

Tightening torque 220~260 180~260 190~220 220~300 220~260 190~220 220~260 250~270 (Nm) 62

YUCHAI Engine Service Manual (6) Measuring of crankshaft axial clearance, refer to Fig. 3-31 and Fig. 3-33. The measured value should meet the requirements listed in table 3-15.

Fig. 3-32 Tightening of main bearing cap bolts Fig. 3-33 Measuring of crankshaft axial clearance Table 3-15 Specified crankshaft axial clearance for each engine model Engine model Axial clearance (mm)

YC6112

YC6L

YC6105

0.10~0.20

YC6108

0.10~0.27

YC4108

YC4112

YC4110

0.07~0.20

YC6M

0.06~0.22

During the inspection, if the measured value is far from specified range in table 3-15, you can select thrust plates with different thickness to meet the requirements. Wear limit should be less than 0.4mm.

TIPS It is better to measure crankshaft axial clearance after the first tightening step of main bearing cap bolts, in case a problem occurs.

334 Maintenance of Crankshaft 1.

If the crankshaft is slightly scratched or burnt (the damage is not obvious), you can polish with abrasive cloth (600 grade) to remove the defect, and method to polish is shown in Fig. 3-34.

2.

If the crankshaft is severely scratched or burnt (the damage is obvious), you can grind the crankshaft to remove the defect and fit with an enlarged shell (+0.25). But when grinding, the requirements regarding crankshaft journal transition fillets (R3 and R5.1) must be addressed. As shown in Fig. 3-35.

3.

When replacing with a new crankshaft, it better to measure dynamic unbalance value with flywheel and clutch assembled. 63

YUCHAI Engine Service Manual Vibration of the engine is mainly caused by oversized dynamic unbalance value of crankshaft module. Including: Crankshaft, flywheel, clutch and pulley damper, these parts have passed tests regarding dynamic unbalance value before delivery. But if the vibration problem is serious, you must check them one by one. Cloth strip

Crankshaft journal

Abrasive cloth

Fig. 3-34 Polishing of crankshaft journal 4.

Fig. 3-35 Machining of crankshaft journal

Deformation of crankshaft: In the process of assembling crankshaft, if found that rotation of crankshaft is not flexible (bearing shells and the shafting fitting hole are in good condition), then the crankshaft may have deformation problem, you should measure crankshaft bending error (refer to Fig. 3-26), if the whole bending error is greater than 0.15mm, the crankshaft should be replaced.

5.

Burning of bearing shell and crankshaft journal.

TIPS If the crankshaft is scratched in peripheral-radial direction (not axially), and the damage length is within 2mm, the crankshaft can be reused after being polished. For most engine models, there are 205 bearing and bearing sleeve installed in crankshaft big-end fitting hole, so please pay attention to this when replacing the crankshaft, do not neglect or misplace. Refer to Fig. 3-29. General rules for select-fit crankshaft bearing shells: When matching crankshaft bearing shells, the color (or color mark) of selected bearing shell should be the same as that of crankshaft main journal, i.e. red to red, blue to blue (or A to A, B to B). According to the A/B color mark on top of main bearing cap, select red bearing shell for A mark and blue for B mark. As shown in Fig. 3-11 and Fig. 3-24. For YC4110, YC4112 and YC6112 engine, because the oil seal seat is installed on engine block to 64

YUCHAI Engine Service Manual fit crankshaft rear oil seal, while for other engine models, the seat is installed on flywheel shell. So the oil seal seat of YC4110, YC4112 and YC6112 engine can be installed at this point. Precautions: (1) Rear oil seal seat gasket should be applied with sealant. Refer to Fig. 3-36. (2) Tighten the bolts according to the order exposed in Fig. 3-37. (3) Clearance between oil seal seat bottom surface and oil sump fitting surface should within 0~0.08mm to prevent oil leaking from oil sump gasket. (4) Apply suitable engine oil on big end of crankshaft when assembling, place a pressing plate and knock it into oil seal seat. As shown in Fig. 3-38. Sealant application

Fig. 3-36 Sealant application position

Rear oil seal

Fig. 3-37 Tightening order of oil seal seat bolts

Pressing plate

Oil seal seat Fig. 3-38 Installation of rear oil seal

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YUCHAI Engine Service Manual

34 Assembly of Piston Connecting Rod Assembly 341 Cleaning of Piston Connecting Rod Assembly Clean the oil holes on connecting rod small end, wipe off the carbon deposit on piston ring grooves and top of piston ring groove, clear away the dirt in engine oil holes connecting rod bolt holes. Refer to Fig. 3-39 and Fig. 3-40.

Fig. 3-39 YC6L piston connecting rod assembly 1 Surface (when connecting rod bolt is loose, this surface will be polished) 3 Oil hole

4 Oil groove

2 Processing number

5 Installing direction mark of connecting rod (face forward)

6 For a few connecting rods, processing number is printed in 7 7 Weight (or weight difference) mark of connecting rod big and small ends

Fig. 3-40 Engine oil gallery in piston 1 Cylinder sleeve

2 Piston

3 Oil gallery

4 Piston hook back-off opening 66

5 Hook

YUCHAI Engine Service Manual

342 Inspection of Piston Connecting Rod Assembly 1.

Inspection of connecting rod (1) Weight difference of connecting rod: allowed weight difference of connecting rod big end, small end, total weight difference and allowed weight difference for the same engine are listed in table 3-16. Refer to Fig. 3-39 for weight (or weight difference) mark of connecting rod big and small ends, choose according to table 3-16 during maintenance.

Table 3-16 Allowed weight difference of connecting rod (g) Engine model YC4108 YC4110 YC4112 YC6105 YC6108 YC6112 Big end allowance Small end allowance Total allowance Allowance for the same engine

YC6L

YC6M

10

10

10

16

16

16

16

16

8

8

8

12

12

12

12

12

15

15

15

20

20

20

20

20

23

(2) Refer to table 3-17, Fig. 3-41 and Fig. 3-42 for measuring of connecting rod big end and small end bore diameter (with shells), and specified value for each engine model

Fig. 3-41 Measuring of big end bore diameter Fig. 3-42 Measuring of small end bore diameter Table 3-17 Specified value of connecting rod big and small end bore diameter (with shells) (mm) Engine model

YC6112, YC4112

YC6105

YC6108

YC4108, YC4110

YC6L

Big end bore diameter Small end bore diameter

74.706~ 74.727 44.452~ 44.459

75~ 75.03 38.01~ 38.02

75~ 75.022 40.01~ 40.02

71~ 71.022 38.01 ~38.02

85~ 85.022 45.01 ~45.02

YC6M 88~88.022 50.01 ~50.02

(3) Measuring of connecting rod distortion error and bending error: refer to Fig. 3-42 and Fig. 3-44.

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YUCHAI Engine Service Manual

Feeler gauge

Piston lock Connecting rod tester Fig. 3-43 Measuring of connecting rod distortion error

Feeler gauge Connecting rod tester

Piston pin

Fig. 3-44 Measuring of connecting rod bending error Distortion error and bending error of connecting rod doesn’t need to be measured under normal circumstance, unless the rod is being hit. Distortion error and bending error of connecting rod should be less than 0.05mm/100mm, while the limit is 0.15mm. 2.

Inspection of piston (1) Piston skirt dimension: Refer to table 3-18 and Fig. 3-45.

Feeler gauge

Fig. 3-45 Measuring of piston skirt dimension 68

YUCHAI Engine Service Manual Table 3-18 Specified piston skirt dimension for each engine model (mm) Engine model

YC6112 YC4112

YC6105

YC6108 YC4108

YC4110

YC6L

YC6M

Diameter of Φ111.634~ piston skirt Φ104.86±0.01 Φ107.87±0.01Φ109.86±0.01Φ112.88±0.07 Φ119±0.01 Φ111.672 biggest circle Wear limit No more than 0.12mm (2) Specified values for diameter of piston pin and piston pin hole are listed in table 3-19. Refer to Fig. 3-46 and Fig. 3-47 for measuring methods. Table 3-19 Specified values for diameter of piston pin and piston pin hole (mm) Engine model

YC6112 YC4112

YC6105 YC6108

YC4108 YC4110

Pin hole Φ44.455~44.461 diameter Pin diameter Φ44.437~44.442 Hole diameter limit Pin diameter limit

YC6M

<0.05 <0.04

Fig. 3-46 Measuring of piston pin hole diameter 3.

YC6L

Fig. 3-47 Measuring of piston pin diameter

Inspection of piston ring should be performed in the process of assembling of piston connecting rod assembly.

343 Assembly of Piston Connecting Rod Assembly 1.

Assembling requirements for piston connecting rod and piston rings: Different engine model has different piston structure, also the incision on connecting rod big end has flat-type structure and oblique-type structure. Section form of piston ring also varies, but a uniform requirement must be met when assembling the assembly. Refer to Fig. 3-48 and Fig. 3-49.

69

YUCHAI Engine Service Manual

View A

View B

Fig. 3-48 Piston connecting rod assembly 1 Mark on top of piston

2 Connecting rod journal

3 Direction of motion

4 Connecting rod number

5 Locating lip and locating groove are on the same side

6 When connecting rod bolt is loose, this surface will be polished 7 Do not interchange or substitute connecting rod bolts 8 Connecting rod cap number (in the same position as connecting rod number) 9 Direction of motion

10 Connecting rod journal

11 This side face has “O” mark (face forward) 12 Hook back-off opening should be on the same side as hook 13 Swirl chamber (no eccentricity for YC6L engine) should be aligned to fuel injectors, view A and View B show the moving direction of connecting rod journal when the piston is in BDC

ATTENTION 1.

If the incision on connecting rod big end has flat-type structure, no facing forward or facing backward problem needs to be addressed (YC4110 engine).

2.

View B in Fig. 3-48 is suitable for assembling of YC6112 and YC4112 engine connecting rod with oblique-type incisions. While view A is suitable for other engines.

70

YUCHAI Engine Service Manual Piston ring No. First piston ring EngineRing type

Second piston ring

Third piston ring

Comment

model YC6108ZQ, YC6112, YC4112, YC6105ZLQ

Double-side Cushion spring Taper-face ring trapezoidal ring oil ring

Ditto YC6108ZLQB, YC4108, YC6L

The first piston ring is chrome-plated, the second piston ring is phosphatized

Ditto

Ditto

Inner chamfer upwards Ditto

Ditto

Ditto

Ditto

Ditto

Ditto

TOP upwards

YC4110

Pin hole

Pin hole Opening of cushion spring Opening of cushion spring

Suitable for YC6113 Engine

Suitable for YC4112 Engine

Pin hole Opening of cushion spring

Suitable for YC6108, YC6105 and YC4108 Engine Fig. 3-49 Installation of piston rings

ATTENTION 1, 2, 3 in the figure above represent piston ring openings. When installing piston ring, you must measure the fitting clearance between piston ring and cylinder sleeve, piston ring and piston ring groove respectively. Measuring method: press the piston 71

YUCHAI Engine Service Manual ring into cylinder sleeve (the cylinder must in TDC position), as shown in Fig. 3-50. Measure the opening clearance with feeler gauge, the measured value must meet the requirements listed in table 3-20. Measure the axial clearance between piston ring and piston ring groove, as shown in Fig. 3-51, the measured value must meet the requirements listed in table 3-20.

Fig. 3-50 Measuring of piston ring opening clearance

Fig. 3-51 Measuring of piston ring axial clearance

Table 3-20 Specified value for piston ring opening clearance and axial clearance (mm) Third piston First piston ring Second piston ring Piston ring opening Engine model ring axial axial clearance axial clearance clearance clearance YC6112, 0.12~0.175 0.105~0.155 0.05~0.1 0.35~0.65 YC4112 YC6108 YC4108

0.065~0.135 0.085~0.135

YC4110 YC6105

0.09~0.125

0.03~0.065

First piston ring 0.4~0.6 Second piston ring 0.35~0.55 0.032~0.065 Third piston ring 0.3~0.55

0.09~0.125 0.05~0.085 0.09~0.13

0.07~0.11

0.04~0.08

First piston ring 0.35~0.55 Second piston ring 0.5~0.7 Third piston ring 0.32~0.55

YC6L

0.108~0.172

0.06~0.11

0.03~0.08

First piston ring 0.30~0.45 Second piston ring 0.60~0.85 Third piston ring 0.32~0.55

YC6M

0.109~0.180

0.075~0.115

0.05~0.09

First piston ring 0.35~0.59 Second piston ring 0.60~0.8 Third piston ring 0.25~0.45

ATTENTION Piston ring opening clearance limit for each engine model is 2mm, and that of piston ring axial clearance is 0.2mm. 2.

Assemble piston connecting rod assembly into engine block. After assembled piston, connecting rod, piston rings and connecting rod bearing shells, install the assembly into engine block according the method exposed in Fig. 3-52. Requirements: 72

YUCHAI Engine Service Manual (1) Connecting rod bearing shells should be applied with clean engine oil. (2) Put the assembly into cylinder sleeve according to the “face forward” mark on piston top surface or connecting rod body. If the mark cannot be read, refer to Fig. 3-48 view A or view B for assembling, ensure swirl chamber in piston is aligned to injectors. (3) Tighten connecting rod bolts to specified torque listed in table 3-21, ensure rotation of crankshaft is flexible, and connecting rod journal can move axially for more than 1mm, and ensure the rod can be stirred easily and flexibly.

Fig. 3-52 Installation of piston connecting rod assembly

ATTENTION In the process of assembling, you must support the big end of connecting rod with special tool or clean board to prevent bumping cylinder sleeve and connecting rod journal. Table 3-21 Specified tightening torque of connecting rod bolts for each engine model (Nm) YC6112 YC6108 Engine model YC6115 YC4110 YC6L YC6M YC4112 YC4108 Step 1 50~80 50~70 60~80 60~90 60~80 Tightening Step 2 100~130 100~120 110~130 100~120 120~150 110~140 torque Step 3 160~190 190~270 180~200 150~230 180~220 160~200 3.

Measure piston protrusion (to engine block upper surface) and adjust TDC scale of cylinder 1. As shown in Fig. 3-53.

Pulley damper assembly

TDC scale Fig. 3-53 Adjust TDC scale of cylinder 1 73

YUCHAI Engine Service Manual Rotate the engine until piston of cylinder 1 reaches TDC, measure the piston protrusion (to engine block upper surface) of each cylinder with dial gauge, which should be 0.15~0.45mm, piston protrusion difference between two cylinders should be less than 0.15mm. If the measured values have big difference, then volume of combustion chamber will be affected, even leading to piston bumping problem.

TIPS When only some connecting rods need to be replaced, you can select-fit according to table 3-17.

344 Common Faults of Piston Connecting Rod Assembly 1.

Connecting rod. (1) Breakage of connecting rod bolts: connecting rod bolts are special purpose parts, you mustn’t replace them with bolts made of other materials. For bolts that have been blued by bearing shell burning or have been tightened and loosened 3 times should be replaced. Breakage of connecting rod bolts is mainly caused by insufficient tightening torque, which made the bolts subject to severe impact repeatedly. At this point, the contact surfaces between bolt head and connecting rod cap are usually brightened and smoothed because of abrasion. Refer to Fig. 3-39. If the connecting rod bolts are burnt blue due to high temperature, then the bolts are deteriorated. (2) After replacing piston pin sleeve (note that oil hole on the sleeve should be aligned to the engine oil gathering hole on connecting rod small end), if fitting clearance between pin and pin hole is too small, you can grind the sleeve or ream/ broach the pin hole to meet the requirements. When reaming, it is better to fix the connecting rod on vertical drill or vertical boring machine and correct perpendicularity of the sleeve hole. Otherwise, parallelism between center line of connecting rod big end hole and that of sleeve hole will be out of tolerance. (3) The connecting rod mustn’t be reused if either of the following situation occurs: connecting rod body turned blue due to piston pin burning or bearing shell burning, connecting rod big end hole is seriously worn due to rotating of bearing shells. (4) Connecting rod bearing shell burning.

TIPS Connecting rod bearing shell burning is mainly caused by poor machining that leading to undersized fitting clearance, as shown in Fig. 3-54. When machining the shell, the section marked with 0.3 and 15 in Fig. 3-54 needs to be removed, which means middle part of the 74

YUCHAI Engine Service Manual shell is thinner than two ends. Test to check whether the shell is qualified: install and tighten the shell to specified torque, sprinkle some read lead on inner surface of the shell and then rotate the crankshaft for a few circles. Disassemble and check the shell: the section marked with 0.3 and 15 in Fig. 3-54 should be free of abrasion, while the processed section near the locating lip should be subject to abrasion. Otherwise, the fitting clearance is too small. Solution: Polish with 180-mesh waterproof abrasive paper. 2.

Piston (1) Scratch on piston skirt: mainly caused by poor lubrication and poor engine oil cooling effect (low engine oil pressure or blockage of hook oil hole, turbocharger-free engine isn’t equipped with this device), which result in engine overheating. Cylinder-scuffing, burn or fracture of piston upper part (above piston ring), causes: bad atomization of fuel injector, even dripping diesel oil (Blockage of fuel injector, low fuel opening pressure), oversized fuel feeding angle, long-time overload low-speed high-temperature running, too much carbon deposit, poor heat dissipation, etc. (2) Piston ring jamming: mainly caused by undersized axial clearance between piston ring and piston ring groove, poor machining of piston ring groove, severe gas carry-over and carbon deposit problem around the piston.

3.

Piston ring (1) Premature wear of piston ring will result in gas carry-over problem in the cylinder (at this point, exhaust gas pressure in engine block increases and some exhaust gas infiltrates into the breather) and engine oil bursting into combustion chamber burning problem (blue exhaust gas, engine oil consumption increased markedly), the main causes are: dirty intake air, long-time overload running or long-time low-speed running. Sometimes this problem will also occur if the piston ring or cylinder sleeve is just replaced, this is because the new piston ring or cylinder sleeve hasn’t been properly run in, and things will get better after working for a while. (2) Breakage of piston ring, primary cause: the piston ring gets stuck and couldn’t rotate any more, at this point, engine oil consumption problem is even severe, working condition of this cylinder getting worse until the ring gets sintered and broken.

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YUCHAI Engine Service Manual

35 Assembly of Engine Oil Pump 351 Cleaning of Engine Oil Pump 1.

If the engine oil pump needs to replaced, you should pour clean diesel oil into the new pump and clean it for a few times, and then pour clean engine oil into the pump to perform the last cleaning (rotate the rotor in this process).

2.

For an old engine oil pump, in addition to clean with diesel oil, all parts must be disassembled and rinsed if necessary.

ATTENTION When disassembling engine oil pump pressure-limiting valve, pay attention to mark the original position of the adjusting plug, for the convenience of assembling.

352 Inspection of Engine Oil Pump YUCHAI products apply two kinds of engine oil pump, namely rotor pump (suitable for YC6112, YC4112, YC4110, YC6105, YC4108 and YC6M engine) and gear pump (suitable for YC6108ZQB and YC6L engine). As shown in Fig. 3-55 and Fig. 3-56.

Fig. 3-55 Structure chart of YC4110 engine oil pump assembly 1 Engine oil pump shaft sleeve (II)

2 Engine oil pump cover

3 Outer rotor

4 Engine oil pump spindle

5 Pump body

6 Safety valve

7 Bolt

9 Safety valve screw

10 Bolt

12 Engine oil pump shaft sleeve (I)

13 Inner rotor

8 Safety valve spring

11 Engine oil pump driven gear

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YUCHAI Engine Service Manual

Fig. 3-56 Structure chart of YC6L engine oil pump assembly 1 Gasket

2 Engine oil pump pressure-limiting valve plug

3 Pressure-limiting valve spring

4 Engine oil pump drive gear

5 Engine oil pump drive gear shaft

7 Engine oil pump idle gear

8 Engine oil pump gear

10 Engine oil pump idler shaft

11 Locating sleeve

6 Engine oil pump cover

9 Engine oil pump driven gear

Main inspection items of engine oil pump: 1.

Meshing clearance between inner rotor and outer rotor (or gears), refer for to Fig. 3-57 and Fig. 3-58.

Fig. 3-57 Measuring of meshing clearance between inner rotor and outer rotor

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YUCHAI Engine Service Manual Reference value 0.025~0.15

Fig. 3-58 Measuring of meshing clearance between gear pump drive gear and driven gear 2.

Clearance between rotor and pump shell end face, refer to Fig. 3-59.

3.

Fitting clearance between rotor and pump shell, refer to Fig. 3-60.

Wear limit of the three above-mentioned clearances should be no more than 0.08mm.

Fig. 3-59 Measuring of clearance between rotor and pump shell end face

Fig. 3-60 Measuring of fitting clearance between rotor and pump shell

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YUCHAI Engine Service Manual

353 Assembly of Engine Oil Pump Engine oil pumps of different engine models are not interchangeable. For YC4112, YC4110 and YC4108 engine, engine oil pump is installed on front end of engine block; for YC6M engine, the pump is installed on front end of engine block, but driven by crankshaft small end, meshing clearance of these engines is guaranteed by machining precision of engine block. For YC6112, YC6105, YC6108 and YC6L engine, the pump is installed on the first main bearing cap or lower surface of engine block, the meshing clearance can be adjusted via the gaskets of engine oil sump fastening bolts. As shown in Fig. 3-61. Adjusting gasket

Meshing clearance 0.045~0.065

Meshing clearance 0.07~0.3

Fig. 3-61 Meshing clearance adjusting of YC6105 engine oil pump

354 Common Faults of Engine Oil Pump 1.

Premature wear of rotor or drive gear and driven gear. Inner and outer rotors (or gears), engine oil pump end cover and shaft sleeve tend to wear prematurely, which will result in engine oil leakage problem and reduce oil pressure. Premature wear is mainly caused by inferior engine oil or unclean engine oil, or engine oil filter failure.

2.

Engine oil leakage caused by loose pump end cover shaft sleeve. This fault is mainly caused by loose fitting between shaft sleeve and the sleeve fitting hole (on pump end cover) or undersized fitting clearance between pump shaft and shaft sleeve, the sleeve gets stuck and rotates along with the shaft.

3.

Engine oil pump body is installed with engine oil pressure safety valve (except YC6105 engine oil pump), you don’t need to adjust this valve under normal circumstance. If you suspect that the pump is in failure after all other oil circuits are confirmed in good condition, you can try to adjust the valve opening pressure, as shown in Fig. 3-55, screw-in the adjusting screw 9 to raise 79

YUCHAI Engine Service Manual engine oil pressure. 4.

Engine oil pump oil inlet joint flange gasket 1 should be flat and free of wrinkle, as shown in Fig. 3-56.

355 Assembly of Engine Oil Cooler Plate-fin engine oil cooler is applied by YUCHAI products, the inner core plate 6 is engine oil circulating cooling passage. A by-pass valve is installed on the cooler, its opening pressure is 0.55MPa. The chamber between core plate 6 and cooler housing is filled with circulating water from water tank to reduce engine oil temperature. As shown in Fig. 3-62.

Fig. 3-62 YC6112 engine oil cooler 1 Cooler cap

2 Gasket (III)

3 Bolt M10×35

4 Gasket (I)

6 Core plate

7 Oil outlet joint

8 Cooler housing

10 By-pass valve spring

11 By-pass valve plug 1.

5 Gasket (II)

12 By-pass valve ball

Cleaning: Focus on the oil passage in core plate 6. Fill the passage with diesel oil and waggle around for a few times, disassemble the by-pass valve and clean the valve spring and inner hole. Record the number of screw-out turns when disassembling the valve, be sure to screw-in the same turns when assembling to avoid changing the valve opening pressure.

2.

Inspection: If engine oil is found in the water during normal use, pay attention to check whether the core plate is loose-welded. The method is: block the oil outlet port of core plate, put the core plate into water and inflate the plate with 0.3MPa air from the oil inlet port to check for air leakage.

3.

Installation: Engine oil cooler is long component, note that the sealing gasket cannot be distorted when assembling, take two steps to fasten the bolts from middle to two ends orderly. 80

YUCHAI Engine Service Manual 4.

Common fault of engine oil cooler is oil leakage problem of the core plate, and there will oil in water under this circumstance, the fault is caused by loose-weld or fake-weld core plate copper pipe joint. Another fault is housing crack or sealing gasket damage.

ATTENTION In cold days, be sure to discharge all water in the cooler to avoid frost cracking.

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36 Assembly of Gear Housing Cover Plate, Camshaft, Idler Shaft and Gearing Housing 361 Assembly of Gearing Housing Cover Plate Gear housing cover plate steel-plate part, two pins are used to locate it on engine block, and fastened on engine block with M8 bolts. When assembling, apply 515 plane sealant on cover plate and fasten the bolts crosswise.

362 Assembly of Camshaft and Camshaft Gear 1.

Cleaning of camshaft Structure and installation method of camshafts applied by YUCHAI products are basically the same. Here we take YC6112 for example, refer to Fig. 2-48. When cleaning the camshaft, focus on oil dirt on camshaft and deposit sediment in the oil holes. For camshaft of YC6105 and YC6108 engine, the oil holes are processed on the third-cylinder and sixth-cylinder position (used to feed oil to rocker arm); for camshaft of YC4108 engine, the oil holes are processed on the second-cylinder and fourth-cylinder position, for camshaft of YC4110, YC4112, YC6112 and YC6L engine, only one oil hole is processed on the first-cylinder position; YC6M camshaft is free of oil hole.

2.

Inspection: check camshaft journal and cam appearance, which should be free of burn damage and scratch, the key groove should be intact. (1) Check camshaft journal diameter, specified camshaft journal diameter for each engine model is listed in table 3-22. Refer to Fig. 3-63 for measuring method.

Fig. 3-63 Measuring of camshaft journal diameter

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YUCHAI Engine Service Manual Table 3-22 Specified camshaft journal diameter for each engine model (mm) Engine model

YC6112 YC4112

YC6105 YC6108

Camshaft journal diameter

Φ60.642~60.688

YC4108

YC4110

YC6L

YC6M

(2) Check camshaft straightness: refer to Fig. 3-64. The straightness error should be no more than 0.05mm.

Fig. 3-64 Measuring of camshaft straightness 3.

Installation of camshaft For the convenience of measuring camshaft axial clearance, generally before installing the camshaft, you should install camshaft timing gear first (refer to Fig. 2-48). Note that fitting clearance between the woodruff key and key groove should not be too big, and fasten camshaft timing gear compression bolt (bolts). Apply engine oil on camshaft journal, hold the camshaft and timing gear with two hands and turn camshaft left and right, push the gear to the right position, the camshaft should be flexible and properly fit. Tighten camshaft timing gear bolts and camshaft thrust pad bolts. Measure camshaft axial clearance according the method exposed in Fig. 3-65. And the measured value should meet the requirements in table 3-23.

Axial clearance

Fig. 3-65 Measuring of camshaft axial clearance

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YUCHAI Engine Service Manual Table 3-23 Specified camshaft axial clearance for each engine model (mm) Engine model Axial clearance Limit 4.

YC6112 YC4112

YC6105

YC6108 YC6L

YC4108

YC4110

YC6M

0.104~0.22

0.16~0.26

0.08~0.20

0.10~0.20

0.05~0.22

0.06~0.22

0.4

Common faults of camshaft Camshaft is a durable part, whose service life is more than 500 thousand kilometers. A few may have problem like burnt by bearing shell. Main causes are: undersized fitting clearance between camshaft and bearing shell or a certain bearing shell is severely worn, severe leakage problem occur and leading to lack of oil of camshaft sleeve. Besides, excessive clearance between camshaft key and key groove will bring severe impact during working, which can affect engine valve timing.

363 Assembly of Idler Shaft and Timing Gear 1.

Installation of idler shaft (1) Clean idler shaft: idler shafts adopted by YUCHAI products are illustrated in Fig. 3-66. Each idler shaft is designed with oil holes and passages to lubricate idler shaft sleeve, make sure these points are unobstructed and clean.

Suitable for YC6108ZLQB, YC6105ZLQ, YC4108ZLQ and YC6L engine

Suitable for YC6112, YC4112 and YC410 engine Anti-wear plate

This oil hole should be aligned to oil hole on engine block when assembling

Oil outlet port

Oil outlet port

Bolt * 3

The bigger chamfer should face engine block

Figure A

Figure B

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YUCHAI Engine Service Manual Suitable for YC6108ZQ and YC6105QC engine

Suitable for YC6M engine

Oil outlet port

Oil outlet port

Oil inlet port

This oil hole should be aligned to oil hole on engine block when assembling Oil outlet port

Figure C

Figure D Fig. 3-66 Structure diagram of idler shaft

(2) Inspection: measure idler shaft diameter and idler shaft sleeve fitting hole diameter, which should meet the requirements listed in table 3-24, each gear tooth face should be free of bumping damage and severe abrasion. Table 3-24 Specified idler shaft sleeve fitting hole diameter and idler shaft diameter (mm) Engine model

Idler shaft sleeve fitting hole diameter/Idler shaft diameter

Fitting clearance

Clearance limit

YC6112 YC4112, YC4110 YC6105

Φ50.813~50.838/Φ50.757~50.770

0.043~0.081

0.2

Φ50.775~50.8138/Φ50.757~50.770

0.05~0.056

/

0.025~0.075

/

0.03~0.09

/

0.043~0.081

0.12

YC6108 YC6L YC4108 YC6M 2.

Installation of idler shaft and timing gear In Fig. 3-66, the idler shaft in Figure C can be assembled independently, while the other idler shafts must be assembled together with idle gear. Here we take YC6112 engine for example, as shown Fig. 3-67.

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YUCHAI Engine Service Manual

Fuel injection pump gear Timing mark

Camshaft timing gear

Steering pump gear Camshaft intermediate gear (idle gear) Crankshaft timing gear Engine oil pump intermediate gear

Engine oil pump gear

Fig. 3-67 YC6112 engine gear transmission

ATTENTION Idler shaft is fixed on engine block with bolts, when assembling idle gear and injection timing gear, pay attention to the following items: (1) Crankshaft timing gear, idle gear, camshaft gear and fuel injection pump gear (except for YC6L fuel injection pump timing gear) are printed with timing mark, these marks should be aligned accordingly when assembling. (2) In Fig. 3-66, idler shaft in Figure A is processed with oil inlet hole, this hole should be aligned to the related oil hole on engine block when assembling. (3) In Fig. 3-66, the anti-wear plate in Figure B should be installed first before assembling the idler shaft, the side with bigger chamfer should face engine block. (4) For Figure A and Figure C in Fig. 3-66, the idler shaft fastening bolt end is installed with baffle plate and locking plate, while the idler shaft in Figure D only installed with baffle plate, and the idler shaft in Figure B takes the shoulder as baffle plate. Install the idle gear on idler shaft and tighten the fastening bolt to specified torque, check the axial clearance between baffle plate and idle gear front end, which should be 0.05~0.38mm. As shown in Fig. 3-68.

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YUCHAI Engine Service Manual Idle gear

Anti-wear plate Support

Tighten the bolt to 203~224Nm

Cylinder block 0.05~0.38mm

Fig. 3-68 Idler shaft axial clearance 3.

Common faults of idler shaft and idle gear (1) Premature wear of idle gear copper sleeve. The main cause is bad lubrication. (2) Idler shaft fastening bolt gets loose, which makes the idle gear swing severely and gear housing produce abnormal noise.

364 Assembly of Gear Housing ATTENTION Gear housing is thin-wall iron casted part, fitting area is large, so pay attention to the following items when assembling: (1) Gear housing sealing gasket should be free of distortion and damage, apply sealant on the gasket when assembling. (2) When assembling crankshaft front oil seal, be sure to fit the seal properly and apply engine oil on the oil seal inner bore. (3) Take two steps to tighten gear housing fastening bolts crosswise and evenly.

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YUCHAI Engine Service Manual

37 Assembly of Air Compressor The air compressor adopted by YUCHAI product varies in engine model, some are wind-cooled, and the others are water-cooled. But their installation methods are generally the same, all fastened on gear housing with three or four bolts. Air compressor intake and exhaust structure is illustrated in Fig. 3-69 and Fig. 3-70.

Fig. 3-69 Helical-spring type air compressor intake principle diagram 1 Valve plate

2 Guide holder

4 Exhaust connecting nut

Valve seat board

Exhaust

Intake

Air intake valve plate

3 Valve seat

5 Cylinder cover

Air exhaust valve plate

Piston

Fig. 3-70 Leaf-spring type air compressor working principle diagram Structure and working principle of the two air compresses in Fig. 3-69 and Fig. 3-70 are similar except the intake valve plate, exhaust valve plate and valve seat, thus installation and maintenance method are basically the same.

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YUCHAI Engine Service Manual

371 Cleaning of Air Compressor Clean the intake and exhaust valve plates, valve seat and piston ring, wipe off the carbon deposit on piston ring. These structures are critical for normal operating of air compressor and demand absolute cleanness.

372 Inspection of Air Compressor Check whether the air compressor intake and exhaust valves are normal. Checking method: 1.

When the air compressor is not working, blow air into the intake pipe on cylinder cover by mouth, the air intake valve is normal if the intake valve plate can open; conversely, absorb air from the intake pipe on cylinder cover by mouth, the air intake valve is normal if no air can be absorbed (intake valve plate cannot open). Checking method for exhaust valve is similar, the air exhaust valve is normal if air cannot be blown into exhaust pipe but can be absorbed from the pipe. For the air compressor in Fig. 3-69, poke the intake valve plate with iron wire, stroke of the valve plate controlled by spring should be 1~1.5mm, otherwise, there must be too much carbon deposit or foreign matters on the valve plate.

2.

When the air compressor is working, block the air intake port by hand and you should feel being absorbed other than pushed, otherwise the intake valve plate is not fully closed. For a normal compressor, the air pressure should reach 0.7MPa or above after about 5min intermediate-speed working. If fail to reach this pressure in 10min, then the compressor is in failure.

3.

Fitting clearance between woodruff key and key groove on air compressor shaft should not be too big, otherwise, the key groove can be easily damaged and cause incorrect fuel supply advance angle.

373 Installation of Air Compressor Air compressor of different engine model is installed on different position, connection type between air compressor gear and intermediate idle gear is different too. For YC6105 and YC4110 engine, air compressor gear is directly connected with intermediate idle gear; for YC4112, YC6108ZLQ, YC6112 and YC6L engine, air compressor intermediate gear is connected with camshaft gear and intermediate idle gear; for YC6M engine, air compressor gear is connected with intermediate gear via camshaft gear.

ATTENTION (1) When assembling air compressor, ensure meshing clearance between each gear pair 89

YUCHAI Engine Service Manual is within 0.07~0.25mm, check and adjust the meshing clearance before fully tightening air compressor fastening bolts. (2) For engine for fuel injection pump is installed on rear end of air compressor (such as YC6105ZLQ), ensure air compressor gear and intermediate idle gear are properly engaged when assembling. (3) When assembling YC4108 air compressor, note that the fastening bolt near engine block is fine tooth thread bolt, do not make mistake.

374 Common Faults of Air Compressor 1.

Premature wear of air compressor piston ring. Service life of a new air compressor piston ring is generally more than 100 thousand kilometers under normal working condition. If the compressor is hard to compress air in 55 thousand kilometers or under, then it can be considered that air compressor piston ring is prematurely worn. The main cause is unclean intake air. Firstly, as an air filter is designed to filter the intake air, improper maintenance of the filter or air leakage problem in intake pipe joint will cause this fault; secondly, poor lubricating of air compressor can accelerate the wear process; thirdly, frequently long-time working of air compressor together with high engine oil temperature can easily cause premature wear.

2.

Too much carbon deposit on intake and exhaust valve plates and valve seat will cause the valve plate unable to close fully. In this case, air compressor cannot work normally and required compression pressure cannot be attained. The main causes are: firstly, unclean air intake by air compressor; secondly, sealing performance between piston ring and cylinder bore is poor, too high air pressure in crankcase (especially when cylinder sleeve and piston ring are severely worn) or intake blockage of air pump can easily lead to bursting up, combustion of engine oil can produce carbon deposit, which can block air hole and make the valve plate unable to close fully. In addition, intake and exhaust valve plate of non-supercharger air compressor applies spring-return mode, if the spring gets soft or inflexible , the valve plate cannot be closed fully either, which will cause air leakage.

3.

Burning of bearing shell: Lubricating oil for air compressor comes from engine, so if the engine oil is inferior, engine oil pressure is abnormal or engine oil gallery is blocked by deposit sediment, lubricating oil to air compressor will be insufficient, and these are main causes for burning of air compressor bearing shell. Besides the caused mentioned above, poor circulating of cooling water is another cause (for supercharger).

4.

Oil leaking from air compressor rear end. The main cause is ageing failure of air compressor crankshaft rear oil seal (Loose air compressor bearing can easily bring oil leakage problem). 90

YUCHAI Engine Service Manual When installing a new air compressor, it’s better to apply suitable engine oil on oil seals. 5.

Engine oil bursts into air compressor exhaust port. The main cause is oversized fitting clearance between air compressor piston ring and cylinder bore or broken piston ring, and blockage of intake, which will cause too much engine oil in air compress and crankcase, and easily result in to engine oil bursting.

ATTENTION If the air compressor bearing (on fuel injection pump side) tends to be damaged easily, please pay attention to check whether coaxiality of air compressor and fuel injection pump meets the requirements, refer to Fig. 3-74.

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YUCHAI Engine Service Manual

38 Assembly of Fuel Injection Pump Fuel injection pump is a key component for engine performance, and special requirements are involved when installing, using, maintaining and troubleshooting it. For YC6112 and YC4112 engine, multiple models of fuel injection pump governor is applied, YC4110 and YC4108 engine apply mechanical maximum-minimum speed governor, and the other engine models adopt RQV-K governor.

381 Cleaning of Fuel Injection Pump Lubrication of fuel injection pump is divided into independent lubrication and forced lubrication. For independent lubrication, it is required to add engine oil into fuel injection pump governor and fuel injection pump body periodically; for forced lubrication, an engine oil pipe that connected to engine block main oil gallery is used to lubricate fuel injection pump, because the oil source is engine oil sump, the clearness of engine oil is hardly assured. Thus, before installing the fuel injection pump you should remove the dust and foreign matters on the pump, and more importantly, you should clean with diesel oil (fill from the engine oil inlet port) to remove the deposit sediment in the pump. Besides, a strainer is installed in oil inlet port of fuel delivery pump, and should be removed and cleaned at the same time.

382 Inspection of Fuel Injection Pump Before assembling the pump, you should check whether the fuel-increase handle and fuel cut-off handle are flexible, check whether there is dirt on fuel delivery joint and clean it. Fuel injection pump of YC6108ZLQB and YC6L engine is designed with timer, when installing the pump, you must make sure the pump is in state of feeding fuel to cylinder 1 (cylinder 1 in TDC), as shown in Fig. 3-71. Disassemble

U-shape gasket

Injection pump shaft Timing indicator pin Timer Assemble Shaft-locking bolt Pump housing

Fig. 3-71 Fuel injection pump timer

Fig. 3-72 VE pump U-shape gasket 92

YUCHAI Engine Service Manual A shaft-locking bolt is installed on left side of VE pump body cold start accelerating advance unit, pressed by a U-shape gasket, as shown in Fig. 3-72. When a new pump is delivered, the pump is adjusted to cylinder-1 fuel-feeding position and no U-shape gasket is needed, pump shaft is pressed by the shaft-locking bolt directly (at this point, please don’t rotate the pump shaft, otherwise the pump can be damaged).

383 Installation of Fuel Injection Pump 1.

For YC6105ZLQ engine, no matter it is equipped with P pump or VE pump, the pump is directly connected with air compressor shaft with connecting plate and two bolts. Firstly you should tighten the pump bracket fastening bolts, and then tightening the connecting bolts between the pump and air compressor. ATTENTION: you must ensure the pump is adjusted to cylinder-1 fuel-feeding position in this process. As shown in Fig. 3-71 and Fig. 3-73. Coaxiality error between fuel injection pump shaft and air compressor shaft should be no more than 0.4mm. Checking method: keep the dial gauge outfit straightly against the excircle plane of advance unit, rotate the advance unit for one full circle and record the gauge maximum reading difference at this same time, and this is coaxiality error. If no dial gauge is available, refer to the method exposed in Fig. 3-74 to do the measuring. Rotate the crankshaft for one full circle, measure the clearance between the measuring screw and advance unit when the measuring screw is in the highest position and lowest position, the clearance should be no more than 0.4mm. When these two marks are aligned, cylinder 1 is being feeded

Shaft-locking mark Woodruff key

Air compressor

Driving shaft

Fig. 3-73 73YC4110VE pump is adjusted to cylinder-1 fuel-feeding position

Fuel injection pump

Fig. 3-74 Measuring of coaxiality error between injection pump shaft and air compressor shaft 1 Connecting bolt 2 Bracket 3 Measuring screw 4 Advance unit 5 Pump support 6 Support screw 7 Pump fastening bolt

If the coaxiality error is too big, you can add suitable gasket on pump support or rotate the pump body to adjust.

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YUCHAI Engine Service Manual 2.

For YC6108ZLQB and YC6L engine, fuel injection pump transmission shaft 4 is connected with fuel injection pump 3, so when installing the pump, you should install the transmission shaft on gear housing firstly, and install pump support 14 on engine block, as shown in Fig. 3-75. And then place the pump on pump support, insert the pump external spline 17 into transmission shaft, press the driving sleeve in position and tighten bolt 9, and then tighten the fastening bolt 8 between fuel injection pump and the driving sleeve, tightening the fastening bolt 13 between fuel injection pump and pump support. Coaxiality between transmission shaft and fuel injection pump is critical for this kind of connection: As long as the external spline can fit flexibly when the adjusting screw plug 6 is not tightened, coaxiality between transmission shaft and fuel injection pump is basically conformed with the request. If the external spline cannot fit-in flexibly, you can wiggle the driving sleeve 7 inward or outward by using the adjusting screw plug 6, or add suitable copper gasket on pump support to solve the problem.

Fig. 3-75 YC6L fuel injection pump assembly 1 Fuel injection pump timing gear fastening bolt 3 Fuel injection pump gear

2 Fuel injection pump

4 Fuel injection pump transmission shaft

5 Connecting bolt between driving sleeve and gear housing cover plate 7 Fuel injection pump driving sleeve

6 Adjusting screw plug

8 Fuel injection pump connecting sleeve

9 Connecting bolt between driving sleeve and engine block 10 Supercharger compensating pipe 11 Throttle switch assembly

12 Fuel cut-off solenoid valve

14 Pump support

15 Fuel injection pump fuel pipe joint

16 Fuel injection pump terminal pad 3.

13 Pump support bolt

17 Fuel injection pump external spline

For YC6M engine, the fuel injection pump and pump gear are connected by coupling. When 94

YUCHAI Engine Service Manual installing the pump, you should install the coupling on gear housing cover plate first, and then install the pump timing gear, install the pump on pump support, and connect the pump and coupling with key.

ATTENTION When installing the pump, you must ensure the pump is adjusted to cylinder-1 fuel-feeding position. As shown in Fig. 3-71 and Fig. 3-83. 4.

Installation of YC4112 and YC6112 engine fuel injection pump. Fuel injection pump of these two engine models is connected with gear housing cover plate by connecting plate, and fastened on pump support. Before tightening the pump fastening bolts, you should insert the timing locating pin into the pin hole on fuel injection pump firstly, rotate the pump shaft left and right until the pin is pressed into the timing plate, tightening the pump fastening bolts and pull the timing locating pin out. At this point, the pump is adjusted to cylinder-1 fuel-feeding position, as shown in Fig. 3-86.

5.

Installation of YC4110 engine fuel injection pump. Fuel injection pump of these two engine models is connected with gear housing cover plate by connecting plate, and fastened on pump support. Advance unit is designed on this kind of fuel injection pump and the pump timing gear is fastened on advance unit with four bolts 8, as shown in Fig. 3-76. Ensure the pump is adjusted to cylinder-1 fuel-feeding position when installing, as shown in Fig. 3-77.

Fig. 3-76 YC4108 fuel injection pump assembly 1 Component of advance unit

2 Injection pump timing gear

3 Injection pump fastening bolt

4 Connecting plate

5 Supercharger compensating pipe

6 Engine oil pipe

7 Bolt

8 Bolt 95

YUCHAI Engine Service Manual

Pump body

Woodruff key

Fig. 3-77 YC4108 pump is adjusted to cylinder-1 fuel-feeding position

384 Common Faults of Fuel Injection Pump 1.

Premature wear of plunger and plunger sleeve. Phenomena: the most common phenomenon is diesel oil leakage problem in pump body. For A type fuel injection pump, bubble will come out from plunger lower spring seat and a significant drop in power is produced when the pump is working at low-middle speed. Fuel feeding quantity for each marked point is hard to be adjusted equally. Causes: too much water content in the diesel oil, fuel filter is damaged or cannot filter normally.

2.

The plunger gets scratched or jammed. Phenomena: fuel feeding rate is reduced, engine speed and power fall simultaneously. Causes: firstly, fitting clearance between plunger and plunger sleeve is too small, overloaded engine plus high engine oil temperature can easily lead to scratching and jamming of plunger; secondly, the fuel filter element is inferior or damaged and the fuel is not properly filtered. Thirdly, delivery valve joint is overly tightened, which can deform the plunger sleeve and jam the plunger.

3.

Breakage of fuel delivery valve and fuel delivery valve spring. Phenomena: the faulty cylinder doesn’t work or work poorly, engine power is reduced. Cause: the part has quality problem.

4.

Insufficient fuel feeding rate of fuel delivery pump. Phenomena: the engine is hard to start or engine speed is hard to increase. Causes: Firstly, filter screen in fuel delivery pump oil inlet joint is blocked (needs to be cleaned), a new engine tends to have this kind of problem more easily, please be sure to clean the filter frequently. Secondly, the check valve is deformed or contains too much dirt (replace or clean). As shown in Fig. 3-78, simple method to check whether the check valve can work normally: absorb air from fuel delivery pump oil inlet port 96

YUCHAI Engine Service Manual by mouth, oil inlet check valve is properly sealed if no air can be absorbed; blow air into fuel delivery pump oil outlet pipe by mouth, oil outlet check valve is properly sealed if no air can be blown in. Thirdly, fuel delivery pump piston is worn, piston spring gets weak or broken, which can result in insufficient fuel feeding rate of delivery pump. Fourthly, the fuel delivery pump has leakage problem. If diesel oil is found when replacing or filling engine oil into the pump housing and the leaked diesel oil is not from plunger, then it must be caused by aging and damaged seal ring of fuel delivery pump roller. Oil seal

High pressure pump cam Roller

Spring Hand pump piston

Oil outlet port

Pump body

Filter screen Oil inlet joint

Check valve

Oil inlet port Oil inlet filter screen Hand pump body Piston

Check valve seat

Fig. 3-78 Working principle diagram of fuel delivery pump 5.

Rough idling of engine. Phenomena: when engine is running at about 750r/min, the rotating speed is sometimes fast and sometimes slow. Causes: Firstly, the preload force of governor idle spring is undersized. Generally, you can adjust the idle adjusting screw on governor to solve this problem. But if you want to deal with this problem thoroughly, you have to disassemble the pump to adjust. Secondly, the pump plungers are unevenly worn, which results in fuel feeding quantity for each cylinder is not equal when the engine is running at idle speed (little influence at high speed).

TIPS (1) Sometimes rough idling occurs when retracting the accelerator pedal, and it seems like the engine is about to flame out at this point. This problem is caused by insufficient preload force of speed regulator stabilizing spring, increase the preload force properly can solve this problem. (2) For engine rough high-medium speed running problem, many causes (such as shape and structure of plunger and fuel delivery valve , and governor) are involved.

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YUCHAI Engine Service Manual 6.

Engine is difficult to start. If the failure is caused by fuel injection pump, then the pump must fail to feed enough fuel for starting. Causes: the plungers are severely worn, severe leakage happens when the engine speed is low or the pump is improperly adjusted. Cause for VE pump: advance unit failure, which can affect fuel feeding timing and make the engine difficult to start.

7.

Insufficient engine power. The so-called insufficient engine power is that the driver can feel the vehicle is hard to speed up on level road (engine fails to reach specified speed) or the vehicle is powerless uphill (engine fails to output specified torque). If the failure is caused by fuel injection pump, then the pump high-speed application point must be improperly adjusted, the pump prematurely reduces fuel feeding rate at high speed, which causes the engine fails to reach specified speed. Handling method: Far better to readjust fuel delivery pump high-speed application point (engine speed at fuel delivery pump high-speed application point is generally about 1.01 times of the rated speed.). A technically skilled maintenance man is able to increase the preload force of the speed governor high-speed spring to improve the pump high-speed application point without affecting other working conditions, as shown in Fig. 3-79; or you can adjust the full-load oil-volume adjusting screw (screw in for about 1/4 circle) on the governor to improve engine speed by increasing fuel feeding rate. High-speed spring Locknut

Upper spring seat

Inner idling spring Outer idling spring

Fig. 3-79 Working principle of flyweight Insufficient engine torque is embodied in poor short-time overload adaptability. If the engine fails to output enough torque at high-medium speed and the problem is caused by fuel injection pump, then the pump application point must be improperly adjusted (rotating speed and fuel feeding rate). To solve the problem thoroughly, you must debug the pump and choose suitable rotating speed and fuel feeding rate for the application point according to the specifications. Refer to table 3-25 for adjusting parameters of some fuel injection pumps.

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YUCHAI Engine Service Manual Fig. 3-25 Adjusting parameters of fuel injection pump Engine model

YC6108ZQ (118kW/2600r/min)

YC4110ZQ (100kW/2800r/min)

YC6112ZLQ (118kW/2600r/min)

Fuel injection pump model

BHT6PN110R092D Hengyang

Rack travel (mm)

11

Rated fuel feeding rate (ml/200 times)

16.6

19.4±0.5/1400r/min

32.5~33/1150 r/min

Torqueing fuel feeding rate (ml/200 times)

19.3

20.4±0.4/800r/min

33.8~34.5/750 r/min

Idling fuel feeding rate (ml/200 times)

2.6

1.25/375 r/min

5.3~6.5/350 r/min

Max. idle speed (r/min)

1380~1480

≤1600 (fuel cut-off speed)

≤1450 (high speed fuel cut-off)

Starting fuel feeding rate (ml/200 times)

16~26/100r/min

＞20/150r/min

≥32/100r/min

BHF4PW110010 Wuxi CB—BH6P120VAV39

Method for RQV-K governor to improve output torque: Remove the boost compensator and then loosen the fastening screw of full-load stop block, move the stop block towards pump body to improve engine output torque (increase torqueing fuel feeding rate by increasing travel distance of control handle). As shown in Fig. 3-80.

Fig. 3-80 RQV-K governor If the engine fails to output enough torque at low-medium speed and the problem is caused by fuel injection pump, then the boost compensator must be improperly adjusted. Adjust the thread sleeve of boost compensator appropriately to reduce preload force of boost compensator spring without affecting low-medium-speed smoke intensity, to increase fuel feeding rate at 99

YUCHAI Engine Service Manual low-medium speed. As shown in Fig. 3-81. Vacuum line

Membrane

Non-Supercharged Fuel regulator Full-load fuel-limiting adjusting nut

Spring

Thread sleeve

Fig. 3-81 Boost compensator 8.

Engine produces black smoke. For this problem, three situations are involved: firstly, black smoke is produced only during starting or at low speed; secondly, black smoke is produced regardless of engine speed; thirdly, black smoke is produced when accelerating. This problem is influenced by many factors, in terms of fuel injection pump, the main cause is too high fuel feeding rate. (1) Black smoke is produced only during starting. The pump is improperly adjusted, too high starting fuel feeding rate of smoke limiter (A type pump) or boost compensator. For VE pump, fuel feeding angle that controlled by cold-start advance unit (KSB) is oversized. (2) Black smoke is produced at low engine speed. The pump is improperly adjusted, too low rotating speed at idle point and fuel feeding rate at this point is oversized. (3) Black smoke is produced regardless of engine speed. The pump is improperly adjusted, fuel feeding rate is too big. Besides, if the pump advance unit loses efficacy, the engine will produce black smoke too. (4) Black smoke is only produced when shifting and accelerating. This problem is caused by mismatch between acceleration of fuel injection pump and changing of engine load, and is related to whether the pump is designed reasonable or not. To solve this problem, you can increase the preload force of boost compensator spring properly to reduce fuel feeding rate.

9.

The pump fuel feeding mechanism is not flexible, which results in unstable working of engine, and impact is involved when traveling. One of the causes is that the plunger is scratched and jammed; the second reason is that idle spring or high-speed spring (used to control flyweight) is broken or dislocated; the third reason is overly tightened fuel delivery valve joint, causing inflexible rotating of plunger (VE pump is free of this phenomenon).

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YUCHAI Engine Service Manual

385 Installation of Fuel Injection Pump Timing Gear Installation method of fuel injection pump timing gear for different engine model is different: 1.

For YC6108ZLQB, YC6L and YC6M engine, the pump is connected with pump timing gear by coupling. When installing the pump, you should install the coupling on gear housing cover plate first, and then install the pump timing gear, install the pump on pump support, and connect the pump and coupling with key. Make sure the pump is in cylinder-1 fuel-feeding position. Method to adjust fuel injection pump feeding position: For YC6108ZLQB engine, the mark on advance unit should be aligned to the pump body cylinder-1 fuel-feeding position, as shown in Fig. 3-82. For YC6L engine, a timer is used for positioning. Rotate the pump camshaft until the positioning block is aligned to the timer notch, and this is cylinder-1 fuel-feeding position, as shown in Fig. 3-71. For YC6M engine, when the mark on connecting set is aligned to the mark on pump connecting plate, the pump is adjusted to cylinder-1 fuel-feeding position, as shown in Fig. 3-83. When the adjustment of cylinder-1 fuel-feeding position is finished, do not rotate the pump shaft any further, and you should install the timing gear on pump shaft and fasten the bolts at this point. Advance unit

Align the marks

Align the marks Pump body

Pump gear transmission shaft

Connecting set

Fig. 3-82 Adjustment of YC6108ZLQB pump 2.

Pump body

Pump connecting plate

Fig. 3-83 Adjustment of YC6M pump

For YC6105ZLQ engine, air pump is connected with fuel injection pump shaft. When assembling, you just need to install the injection pump timing gear and idle gear on air pump shaft by aligning the timing marks, and then fasten the bolts.

3.

For YC4110 and YC4108 engine, the pump timing gear is fastened on advance unit with bolts, and the advance unit is connected with pump shaft by woodruff key. When assembling, you should set the pump to cylinder-1 fuel-feeding position firstly, as shown in Fig. 3-84. And then install the advance unit, as shown in Fig. 3-76.

101

YUCHAI Engine Service Manual Woodruff key

Locking mark

Driving shaft

Fig. 3-84 Cylinder-1 fuel-feeding position of YC4110 fuel injection pump

ATTENTION When the locking mark is aligned to the mark on woodruff key, the pump is adjusted to cylinder-1 fuel-feeding position. 4.

For YC4112 and YC6112 engine, you should assemble the timing gear housing cover plate and crankshaft damper first, and then install the pump timing gear.

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YUCHAI Engine Service Manual

39 Assembly of Damper Different engine models apply different dampers, but they are all installed on small end of crankshaft. Two kinds of dampers are adopted by YUCHAI products, namely rubber damper and silicone oil damper. Some of YC6112, YC6108 and YC6105 engines apply silicone oil damper, as shown in Fig. 3-85. Before the assembling, you should check damping rubber and the shell for looseness, fitting clearance between key and key groove mustn’t be oversized, otherwise it may damage the damper. Rear damper

Front damper

Timing gear housing cap Crankshaft Fastening

Key Base plate

Hexagon bolt Before assembling, you should apply graphite-containing engine oil on this surface Radiator fin (casted in rear damper)

Fig. 3-85 YC6112 engine damper

TIPS For some engine models, interference fit is adopted between damper and crankshaft small end, and no key and key groove is needed, but assembled with special tools. The damper may rotate if the interference value is undersized, valve timing may change under such circumstance. Use pulley disassembling tools to assemble the damper, never knock fiercely and blindly to prevent damaging pulley and damper rubber. Major failure of damper is fall-off of damper rubber, which is mainly caused by uneven force on each pulley belt (installation position of A/C is not reasonable) and loose belt, leading to excessive vibration of damper. After the belts are assembled, align the TDC marks: rotate the crankshaft until piston of cylinder 1 reaches compression TDC, check whether the TDC pointer on front end of engine block is aligned to “0” mark on pulley, align them if not. Steps to assemble YC4112, YC6112 fuel injection pump timing gear: 103

Fuel injection timing adjustment（YC4A105 stage Ⅱ）

4 3 1 2 1 Fuel injection pump connecting plate

2 Fuel injection pump

3 Fuel injection pump gear connection plate

4 Fuel pump gear

1.First, connect 1 fuel pump connection plate and 2 fuel injection pump 2.Install the assembly on the body and lock it 3.Install 3 injection pump gear connection plate on the pump shaft and lock with large nut 4.Turn the large nut to observe the first cylinder fuel injection port and turn it to the first cylinder oil port to generate fuel. Then the crankshaft is reversed at a certain angle, slowly turning forward, carefully observe the oil level at the oil pipe joint. When the oil surface starts to move, stop rotating immediately and find the first cylinder fuel injection point. 5.Install 4 fuel injection pump gears, pay attention to the alignment of the marks, do not lock the oil pump gears

6. Rotate the crankshaft counterclockwise 15° and use the pressure plate to lock the 4 gears and the 3 fuel injection pump gear connection plate to complete the fuel injection pump installation.

YUCHAI Engine Service Manual Step 1: Rotate the crankshaft until piston of cylinder 1 reaches compression TDC, align the TDC pointer on front end of engine block to required fuel feeding angle mark on pulley, stop rotating the crankshaft. Step 2: Rotate the fuel pump camshaft until the centering pin hole on inner timing plate is upright, install the timing gear and gear compression plate, insert the timing locating pin into the holes on pump gear compression plate, timing gear connecting plate and inner timing plate, as shown in Fig. 3-86. The pump is adjusted to cylinder-1 fuel-feeding position when the four holes are aligned. Step 3: Tightening the pump fastening bolts and pull the timing locating pin out.

TIPS At this point, the fuel feeding angle is not necessarily accurate, and you should check it again when test-run the machine. The method is: remove the connecting nuts between high pressure fuel pipe of cylinder 1 and fuel injection pump, and then rotate the crankshaft, stop rotating when the oil in cylinder-1 fuel delivery valve seat joint is surging up slightly, loosen the four fastening bolts of fuel injection pump. Rotate the crankshaft left and right until required fuel injection angle is acquired, install the four fastening bolts.

O-ring

Locating pin Inner timing plate Locating pin

Fuel injection pump and compression plate Bolt

Fig. 3-86 YC6112 engine fuel-feeding timing

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YUCHAI Engine Service Manual

310 Assembly of Engine Oil Sump and Components Inside 3101 Oil Strainer Assembly Structure of oil strainer assembly is very simple, but attention should still be paid to the requirements regarding its installing and maintaining, because it will always have the possibility of failure. The oil strainer assembly structure is shown in Fig. 3-87. Oil dirt and debris on the strainer must be cleared away. During assembly or subassembly, gaskets must not be distorted or damaged. When installing engine oil pump, the flange gasket 1 must be flat and free of wrinkle, requirements for oil pump outlet pipe flange gasket are the same. For support plate of strainer oil pipe, no crack is allowed, and no deformation or big distortion to the plate after assembling to prevent damage under severe vibration. Flange gasket should not be reused. If strainer gets clogged during working, engine oil pressure gauge might indicate no pressure change or little pressure change when engine accelerates from the idle speed to high speed, or engine oil pressure can reach 0.1~ 0.2MPa when starting, but nearly no pressure rise after accelerating. This is because the strainer is partially blocked.

Fig. 3-87 YC4108 engine oil strainer 1 Gasket assembly

2 Oil absorption pipe weldment

3 Bolt M8×50

4 Bolt M8×50

5 Strainer

6 Strainer support

3102 Assembly of Engine Oil Sump The oil sump is a thin-walled part, and generally you should not hit it fiercely, so as to avoid deformation which affects use. A gasket is installed between oil sump and engine block for sealing, so the gasket must be completely free of damage. When installing, exert your strength diagonally and evenly, especially for the fitting surface between gear housing and oil sump front end, no protrusion to the engine block lower plane is allowed, otherwise the oil sump won't be able to be sealed. 105

YUCHAI Engine Service Manual

TIPS An oil drain plug is installed on bottom of the oil sump, there is a magnet inside the plug, which is used to absorb and collect scrap iron in engine oil. After a period time of working, you should drain out the engine oil and check whether there is scrap iron on the plug, find out the and cause and eliminate the problem if so. As shown in Fig. 2-58.

311 Output End Components (Flywheel, Clutch and Flywheel Shell) 3111 Flywheel and Gear Ring Assembly Interference fit is adopted between flywheel and gear ring assembly. When assembling them, you should heat gear ring to above 120oC firstly, and then press it into the flywheel. Heating method: generally heat it directly with fire is feasible. Do not heat it with blow torch or acetylene flame, because it may cause inhomogeneous heating, and high local temperature may soften the gear ring. Common faults: 1.

Looseness of gear ring: The main reason is that the fit clearance between the flywheel and gear ring is too large.

2.

Bump damage on gear tooth surface: Firstly, this may be caused by time mismatching between motion of starter gear (trigged by starter electromagnetic switch) and power on of the motor (quality problem of own); secondly, it may be caused by deformation of the starter motor gear tooth, which will result in poor engagement problem (repair the tooth surface can solve this problem).

3.

Deflection or vibration of the flywheel: For this problem, you need to check if the runout of crankshaft big end face (to the axis) is within the prescribed range (less than 0.038 mm), and whether flywheel bolts are evenly tightened.

TIPS Pay attention to check if the flywheel bolt and depth of bolt hole match.

3112 Clutch 1.

Inspection of clutch Inspection: Damper spring mustn’t be broken, all rivets mustn’t be loose, driven plate body mustn’t be fractured, friction plate mustn’t be delaminated or with large crack. The diaphragm and separation claw should be in the same plane in principle, at least the height difference should be less than 0.4 mm. The clutch counterweight should be installed in its original 106

YUCHAI Engine Service Manual position. 2.

Installation of clutch Before the installation of clutch, you should clear away oil dirt and foreign matter on the friction plates. Connecting bolts between clutch cover and the flywheel should be fastened uniformly in diagonal way.

3.

Clutch common faults (1) Clutch slipping: Slipping phenomenon mainly manifested in incomplete output of engine working torque, poor loadability and burning of clutch friction plate, and when the problem gets more serious, it may be difficult to start the engine. The main causes are: undersized free stroke of clutch pedal, too small clearance between release bearing and release lever, too much oil dirt or delamination crack on clutch surface, and burned off layer, and insufficient force of pressure spring. (2) Dragging and shaking of clutch. The main causes are: oversized free stroke of clutch pedal, which may put the clutch in semi-contact status; release spring gets softened, broken or unbalanced; misadjusting of clutch middle pressure plate stop screw; the driven plate is wrongly installed (positive & negative); faults in main hydraulic cylinder and booster cylinder (for hydraulically operated clutch). (3) Clutch produces abnormal sound. The abnormal sound is caused by bumping or scraping. The main causes are: release bearing is damaged, and its rotation is not flexible and produces abnormal sound; looseness or breakage of driven plate steel disc or rivet, which will result in bumping problem; abrasion and looseness of release lever, control mechanism is stuck and inflexible, which may result in colliding of friction plates; likewise, abrasion and looseness of clutch middle pressure plate pin hole and pin can also produce abnormal sound.

3113 Installation of Flywheel Shell 1.

Installation: connect the flywheel shell to the rear end of engine block, and take two steps to tighten the bolts to required torque with the stipulated torque crosswise, and check the coaxiality between flywheel shell stop groove (locating surface, such as surface A in Fig. 3-88) and crankshaft axis, as shown in figure 3-88. Measuring method: attach the magnetic dial indicator seat to crankshaft big end, stick the meter header vertically the stop groove (surface A) (preload the meter header for about 1~2mm), rotate the crankshaft for one circle and record the maximum reading on the meter, and that is coaxiality error between flywheel shell stop groove and crankshaft axis. The coaxiality error should be no more than 0.4mm, if fail to meet the 107

YUCHAI Engine Service Manual requirements, you can loosen flywheel shell fastening bolts and adjust, tighten the bolts and measure again. If still fail to meet the requirements, replace the flywheel shell and check again.

Surface A Dial indicator

Flywheel shell

Surface A

Flywheel shell

Dial indicator Crankshaft Crankshaft

Rear oil seal Assembly diagram of YC6105, 4108, 6108, 6L, 6M flywheel shell

Assembly diagram of YC112, YC4112, YC4110 flywheel shell

Fig. 3-88 Flywheel shell and crankshaft 2.

Flywheel shell common fault is breakage of flywheel shell fastening bolt. One of the main causes is that the flywheel shell wall is too thin and fails to meet the requirements. The second reason is that the coaxiality error between flywheel shell and crankshaft axis is oversized. If the crankshaft bearing is severely worn, vibration of engine can easily crush and damage flywheel shell. The third reason is matching chassis failure, which can result in severe engine vibration, and pay attention to this during maintenance.

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YUCHAI Engine Service Manual

312 Assembly Of Cylinder Cover and Its Parts 3121 Cleaning of Cylinder Cover 1.

Clean way the dust, carbon deposit, oil dirt, water scale, and rust on the cylinder cover.

2.

Clean the water channels, oil galleries and air passages with diesel or detergent.

3.

If there is too much rust or blur, remove them with spatula or 0# sandpaper.

4.

Blow-dry the water channels and air passages in cylinder cover.

3122 Inspection of Cylinder Cover (Mainly For Used Cylinder Cover) 1.

Check cylinder cover appearance for big bump damage and crack, a cracked cylinder cover mustn’t be reused.

2.

Measure valve sinkage, as shown in Fig. 3-89, which should meet the requirements listed in table 3-26, wear limit should be no more than 2mm, otherwise the valve seat ring or valve must be replaced.

Fig. 3-89 Measuring of YC6105 engine valve sinkage Table 3-26 Standard valve sinkage YC6108, YC6108ZQB, Type YC6105, YC6108ZLQB YC4108 Value (mm)

3.

0.8~1.2

1~1.3

YC6112 YC4112

0.84~1.32

YC4110

0.75~0.95

YC6L

YC6M

Intake 0.59 Exhaust 0.5

Intake 1.3~1.6 Exhaust 1.12~1.4

Measure valve seat ring sealing strip width, refer to Fig. 3-90 If the valve seat ring sealing strip width (or sealing strip width) is too small, the sealing performance is good, but related parts easy to wear; if the valve seat ring sealing strip width (or sealing strip width) is too large, leakage problem may occur and related parts easy to burn. So valve seat ring sealing strip width is generally controlled within 2.5mm. Grinding with reamer 109

YUCHAI Engine Service Manual or replace it if out-of-tolerance. Valve seat

Fig. 3-90 Inspection of valve sealing strip width 4.

Measure fitting clearance between valve guide pipe and valve, as shown in Fig. 3-91, the measured value should meet the requirements listed in table 3-27. Borescope Micrometer

Fig. 3-91 Measure the valve guide pipe bore diameter Table 3-27 Fitting clearance between valve and valve guide pipe Fitting Engine model YC6112 YC4112 YC6M YC6108 YC6L YC4108 YC6105 YC4110

Specified value (mm)

Fit tolerance (mm)

Intake Ф9.469~Ф9.495/Ф9.46~Ф9.446

0.025~0.069

Exhaust Ф9.469~Ф9.495/Ф9.401~Ф9.418

0025~0.094

Intake Ф12.000~12.018/Ф11.90~11.94

0.060~0.118

Exhaust Ф12.000~12.018/Ф11.90~11.94

0.060~0.118

Intake Ф9.5~9.519/Ф9.401~9.418

0.082~0.118

Exhaust Ф9.5~9.519/Ф9.401~9.418

0.082~0.118

Intake Ф9.500~9.519/Ф9.483~9.475

0.025~0.060

Exhaust Ф9.500~9.519/Ф9.483~9.49

0.040~0.081

Intake Ф9.500~9.519/Ф9.453~9.475

0.025~0.066

Exhaust Ф9.500~9.519/Ф9.438~9.46

0.040~0.081

Intake Ф9.469~9.495/Ф9.401~9.418

0.025~0.069

Exhaust Ф9.469~9.495/Ф9.401~9.018

0.051~0.094

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YUCHAI Engine Service Manual 5.

Inspection of valve sealing performance, as shown in Fig. 3-92. Fill up the to-be inspected valve head with gasoline or kerosene, and let it stand for about 3min, the sealing performance is good if no leakage phenomenon occur. Otherwise, you should grind the valve sealing strip, or do the grinding work after reaming, as shown in Fig. 3-93 and Fig. 3-94. If grinding or reaming is temporarily unavailable, you can knock the valve big-end head for temporary use.

Fig. 3-92 Inspection of valve sealing performance

Fig. 3-93 Reaming valve sealing strip

Fig. 3-94 Grinding valve sealing strip

ATTENTION Valve seat angle for different engine models are listed in table 3-28. Table 3-28 Valve seat angle. Engine model YC6105 Item YC6112

YC4112

YC6L YC6M

YC6108 YC4108

YC4110

Intake valve seat angle

120°

110°

90°

Exhaust valve seat angle

90°

90°

90°

3123 Installation of Cylinder Cover Parts 1.

Installation of the valve guide: YC6L engine adopts 4-valve-per-cylinder cylinder cover, while the other engines adopt 2-valve type. Valve guide pipe is standard component that has been installed in cylinder cover before delivery by the manufacturer, so when replacing it during maintenance, it is better to machine a 111

YUCHAI Engine Service Manual dedicated tool to install it, as shown in Fig. 3-95, note that the end with bigger chamfer should be upward. To prevent deforming the guide pipe during assembling, it is better to cool it with liquid-nitrogen for 10~15min before installing. If inner bore of the guide pipe is deformed after assembling, be sure to ream it with suitable reamer as long as the valve can move up and down flexibly. Bigger than the bottom chamfer

Fig. 3-95 Installation of valve guide pipe 2.

Installation of valve seat ring Valve seat ring has been installed in cylinder cover before delivery. When replacing the valve seat ring, you should cool the new retainer with liquid-nitrogen for 10~15min and press it in with dedicated tool, as shown in Fig. 3-96.

ATTENTION Chamfer is designed on one end of the valve seat ring for convenience of assembling. The valve seat ring has been preliminary reamed before delivered together with cylinder cover, but not to its use standard, you should grind it to match the new valve before use. As shown in Fig. 3-94.

Figure 3-96 Installation of valve seat ring 3.

Adjusting of fuel injector protrusion Fuel spray angle and spraying position in combustion is directly influenced by fuel injector protrusion (refer to Fig. 3-97). Fuel spray angle and spraying position can directly affect fuel combustion quality, if the spray angle and spraying position meet the requirements, the fuel can 112

YUCHAI Engine Service Manual be fully combusted with good combustion quality; conversely, the fuel combustion will be poor and incomplete. So fuel injector protrusion is vitally important and should be properly controlled. Refer to table 3-29 for standard fuel injector protrusion of different engine models, if the measured value is not in the specified range, you can add gaskets to meet the requirements.

REQUIREMENT Prior to the measuring, be sure to assemble the injector into cylinder cover and tighten the fastening bolt/nut to specified torque.

ATTENTION For some models such as YC6105 YC6108, you should install the injector copper bush 5 and then install the injector assembly.

Injector protrusion

Fig. 3-97 Measuring of fuel injector protrusion 1 Cylinder cover

2 Valve guide pipe

3 Injector adjusting gasket

4 Injector adjusting gasket

5 Injector copper bush

Table 3-29 Standard fuel injector protrusion Engine model YC6112 Item YC4112

YC6105

YC6108 YC4108

YC6L

YC6M (M3400)

YC6M (M3000)

YC4110

Protrusion (mm)

3.9±0.1

3.5±0.1

2.5±0.1

2.4±0.1

4.1±0.15

3.6±0.1

4.

3.4±0.1

Installation of air valve (1) Number of valve springs for different engine model is listed in table 3-30, refer to Fig. 3-98 for installation order. (2) When installing valve lock clamp, you should firstly press down the spring seat together with the valve spring, and then install the valve lock clamp in place, shock the spring with hammer to set the valve lock clamp in place completely after installing, rotation of valve must be flexible after cylinder cover is installed. As shown in Fig. 2-42.

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YUCHAI Engine Service Manual Table 3-30 each type valve spring Item Intake valve Exhaust valve Intake valve Exhaust valve Engine model spring spring oil seal oil seal

Method

YC6112 YC4112

1

1

1

1

Commonly used

YC6108 YC6105 YC4108 YC4110

2

2

1

1

Commonly used

YC6L

1

2

1

YC6L

Outer spring is not universal

YC6M

Inter spring is universal. Exhaust valve outer spring is a circle higher than intake valve outer spring.

YC6M

2

2

2

ATTENTION YC6112 and YC4112 engine exhaust valve rod is installed with a spring seat sleeve, other models is free of this part, refer to part 7 in Fig. 3-98.

Fig. 3-98 YC6112 valve rocker arm module 1 Intake valve 5 Valve rod oil seal

2 Exhaust valve

3 Exhaust valve seat ring

6 Exhaust valve spring seat

8 Valve lock clamp 9 Intake valve spring seat 12 Pushrod

7 Exhaust valve spring seat sleeve

10 Intake valve seat ring

13 Rocker arm shaft support

17 Intake valve rocker arm

19 Cylinder cover (long one) 20 Lock nut 114

11 Tappet

14 Exhaust valve rocker arm bush

15 Exhaust valve rocker arm 16 Rocker arm shaft spring 18 Intake valve rocker arm bush

4 Valve spring

21

Adjusting

YUCHAI Engine Service Manual screw 5.

Installation of cylinder cover (1) Installation of cylinder cover gasket: cylinder cover gasket is divided into two types, namely unitary type (one gasket for one engine) and split type (one gasket for one cylinder cover). Divides according to structure, some cylinder cover gaskets are of hybrid type (asbestos plus steel disc), some are of single steel disc type. YC6L engine adopts unitary single steel disc cylinder gasket; while YC6M engine adopts split-type single steel disc cylinder gasket. YC6112 (300PS is of single steel disc type), YC4112, YC6105, YC6108 (YC6108ZC is of single steel disc type), YC4110 and YC4108 engine are designed with hybrid type cylinder gasket, pay attention to the front and back when assembling, the front side should be upward and fit with cylinder cover bottom surface, as shown in Fig. 3-99.

Fig. 3-99 Cylinder cover gasket (front side upward) (2) Connect cylinder cover to engine block, locating sleeves are used to position cylinder cover and engine block. When fastening cylinder cover bolts, you should take three steps to tighten the bolts to required torque according to the order listed in Fig. 3-100, required cylinder cover bolt tightening torque is listed in table 3-31.

Fig. 3-100 YC6112 cylinder cover bolts tightening order Table 3-31 Standard cylinder cover bolt tightening torque Engine model

YC6112 YC4112

YC6105

YC6108 YC4108

YC6L

Torque Nm

200~230

160~230

210~250

210~250

115

YC6M

YC4110

Main bolt: 250~270 180~260 Auxiliary bolt: 150~200

YUCHAI Engine Service Manual

TIPS YC6M engine adopts split-type cylinder gasket (one gasket for one cylinder cover), prior to fastening cylinder cover bolts, you should connect the exhaust pipe to cylinder cover and fix it with bolts, otherwise the exhaust pipe joint may have air leakage problem. For YC6M engine, there are two kinds of cylinder cover bolts, namely main cylinder cover bolts and auxiliary cylinder cover bolts, the main bolt head is bigger, tighten torque of main cylinder cover bolts and auxiliary cylinder cover bolts are different, please pay attention to this. 6.

Installation of valve rocker arm and rocker arm shaft (1) Valve rocker arm is divided into intake valve rocker arm and exhaust valve rocker arm. For all engine models except YC6M, the rocker arm is designed with rocker arm shaft sleeve. Two kinds of lubricating methods for rocker arm are involved, as shown in Fig. 3-101 and Fig. 3-102. Valve adjusting screw

Rocker

Pushrod Rocker shaft seat Engine oil outlet

Engine oil inlet Valve adjusting screw

Tappet Rocker

Rocker shaft Rocker seat Engine oil inlet

Rocker shaft Notes:

Represents YC6L lubricating oil route Represents YC6M lubricating oil route

Fig. 3-101 YC6108 rocker arm

Fig. 3-102 YC6L and YC6M rocker arm lubricating

oil route (2) Rocker arm shaft: YC6112，YC4112 and YC4110 engine adopt unitary rocker arm shaft (one shaft for one engine); while YC6105, YC6108 and YC4108 engine have two rocker arm shafts respectively; YC6L and YC6M engine adopt spit-type rocker arm shaft (one shaft for one cylinder), as shown in Fig. 3-103.

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Fig. 3-103 YC6L engine valve tappet assembly 1 Tappet

2 Pushrod bottom ball

3 Pushrod body

4 Pin 6×12

5 Rocker arm

seat 6 Locating sleeve

7 Flat gasket

8 Spring washer

9 Bolt M10×80 10 Pushrod head

11 Bolt M8×40

12 Flat gasket

13 Spring washer

14 Rocker arm shaft 15

17 Lock nut

18 Valve rocker arm bush 19 Valve rocker arm 20 Ball

Round

pin 16 Adjusting screw head 21 Ball head cushion block 25 Valve inner spring

22 Valve bridge

26 Valve outer spring

23 Valve lock clamp

24 Valve spring seat

27 Exhaust valve

28 Intake valve

The end with groove should face front end of engine Rocker shaft support Spring

Rocker Fixing bolt * 7

Fig. 3-104 Rocker arm shaft mark 117

YUCHAI Engine Service Manual (3) Requirements for installation of rocker arm shaft and rocker arm: Firstly, install related parts on rocker arm shaft and rocker arm shaft seat; secondly, for YC6L engine, oil inlet hole on rocker arm seat must be aligned to oil hole on cylinder cover; thirdly, for YC6112 and YC4112 engine, one end of rocker arm shaft is processed with groove, the end with groove should face front end of engine, as shown in Fig. 3-104; fourthly, oil inlet hole or groove on rocker arm shaft should face downward when assembling, otherwise oil inlet passage of rocker arm shaft will be blocked; fifthly, when installing rocker arm of YC6L engine, the injector assembly and valve bridge must be assembled together, as shown in Fig. 3-105.

Fig. 3-105 YC6L engine injector assembly 1 Nut M8

2 Gasket

3 Packing washer

6 Injector

7 Injector gasket

4 Injector pressing plate

5 Stud M8×35

When installing the valve bridge, the end with back-off groove should face exhaust pipe, as shown in Fig. 3-106. Back-off groove

Fig. 3-106 Valve bridge

118

YUCHAI Engine Service Manual Refer to Fig. 3-107 for installation of YC6L engine injector assembly. Pressing plate Seal ring Bolt

Locating groove Locating ball O-shape seal ring Pressing sleeve High pressure fuel pipe joint Fuel return pipe joint

Injector assemlby

Cylinder cover

Protrusion adjusting gasket

Fig. 3-107 Installation of YC6L engine injector assembly Step 1: Press the injector assembly into cylinder cover fully, note that the adjusting gasket mustn’t be lost, and fuel inlet hole on injector should be aligned to high pressure fuel pipe joint. Step 2: Press the high pressure fuel pipe joint into cylinder cover fully and pre-tighten it, pre-tighten the locating groove to 10~20Nm. Step 3: Tighten the pressing sleeve first, and then tighten the pressing plate fastening bolts (never tighten the pressing plate fastening bolts first). Step 4: Tighten the pressing sleeve to specified torque 35Nm. 7.

Installation of injector assembly The quality of injector can greatly affect engine performance, so adjusting and inspection of injector is vitally important. (1) For a used injector, you must clean the nozzle with gasoline or detergent to remove the carbon deposit, otherwise this will have impact on atomization effect, heat dissipation effect will also be affected. (2) Inspection of injector: mainly check whether the injector atomization effect meets the requirements at rated opening pressure. Injector of YUCHAI products adopt two kinds of pressure adjusting forms: for the first kind, pressure adjusting spring is used to adjust fuel injection pressure, as shown in Fig. 3-108; for the second kind, fuel injection pressure is adjusted by adding subtracting adjusting gaskets 9, as shown in Fig. 3-109.

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Fig. 3-108 Injector with pressure adjusting spring 1 Fuel return pipe joint

2 Adjusting screw fastening cap

3 Adjusting screw

4 Fuel inlet pipe joint

5 Pressure adjusting spring

6 Thimble

7 Injector nozzle matching part

8 Needle valve

Fig. 3-109 Injector with pressure adjusting gaskets 1 Fastening cap

2 Cushion block

3 Hole

6 Screw cap

7 Needle filter

8 Fuel return joint

9 Adjusting gasket

11 Lower spring seat

12 Locating pin

10 Pressure adjusting spring 13 Needle valve matching part

120

4 Injector body

5 Fuel pipe

YUCHAI Engine Service Manual Required injector opening pressure for each engine model is listed in table 3-32, and refer to Fig. 3-110 for inspection and adjusting method. Table 3-32 Engine model

YC6112 YC6108

YC4112

YC6105

YC4108

Opening pressure (MPa)

25~26

26~27

22~24

25~26

YC4110

YC6L

YC6M

25.5~26.5 27.5~28.3 23.5~25.5

Fig. 3-110 Inspection of injector opening pressure

TIPS 1) Requirements for adjusting of injector opening pressure: the opening pressure must within the required range, injected diesel oil must be atomized enough and has a certain spray angle, more importantly, and the injector should be free of fuel dripping phenomenon when the injection process is finished. When inspecting, you should operate the handle at a speed of 100 times per minute to check atomization effect. If the fuel can only be properly atomized at high operating speed and bad atomization effect or dripping fuel at low operating speed, then it means that the engine low-speed performance is definitely poor, generally the engine produces black smoke at low speed. 2) Selection of injector opening pressure: in a certain pressure range, the higher the selected injector opening pressure, the larger the engine output power, but the noise increases too; on the contrary, the lower the selected injector opening pressure, the smaller the engine output power, but the noise decreases too, therefore you should select suitable opening pressure based on real working condition. (3) When installing injector assembly into cylinder cover, note that the protrusion adjusting gasket mustn’t be lost; when installing injector high pressure fuel pipe, be sure to take three steps to tighten the thread sleeve on both ends of the pipe crosswise, the pipe may crack if 121

YUCHAI Engine Service Manual directly tighten the sleeve on one end to required torque.

3124 Common Faults of Cylinder Cover Parts 1.

Cylinder cover Cylinder cover is cracked and leaking water, generally the cracked area is between two adjacent cylinders, the nose bridge and swirl chamber. Main causes are: casting defects, cylinder cover wall is thin, too large fuel feeding rate, early fuel timing and bad atomization, which will result in oil leakage problem, long combustion time and high engine temperature, the cylinder cover will crack if filling cold water to an overheated engine.

ATTENTION For YC6105 and YC6108 engine, the water in cylinder cover will leak into combustion chamber if the injector copper bush is loose and cracked. 2.

Premature wear of valve and valve seat ring: main causes are unclean intake air, oversized intake valve clearance, undersized exhaust valve clearance and valve burning.

3.

Valve head is cracked, main causes are: the valve own quality problem, oversized valve clearance and results in knocking problem; for a vehicle equipped with exhaust brake, if the exhaust brake is clogged, exhaust bounce-back phenomenon may occur, which can easily lead to fall off of valve lock clamp and damage the valve.

4.

Premature wear of valve rocker arm shaft, valve head (the end with adjusting screw), contact surface between valve rod head and rocker arm, causes: engine oil pressure is low, insufficient lubricating of rocker arm; lubricating oil from rocker arm fails to get to adjusting screw and valve rod head and result in dry friction due to unreasonable structure and shape of rocker arm.

5.

Rocker arm shaft module: burning of rocker arm copper bush and rocker arm shaft. Main causes: engine oil pressure is low and fails to lubricate the rocker arm; the nuts of oil pipe on rocker arm seat are loose and leaking oil or the oil pipe is cracked.

6.

Burning or seizure of tappet, tappet of YC4108, YC6105, YC6108 and YC6L engine is lubricated by engine oil from cylinder cover rocker arm, if engine oil pressure is low or fitting clearance between tappet and engine block is too small, a dead end oil chamber will be formed and will accumulate dirt, which will result in burning damage; besides oil from cylinder cover rocker arm, tappet of YC4110, YC4112, YC6112 and YC6M engine is also lubricated by engine oil from main oil gallery, so the common fault of the later four engine models is seizure of tappet.

7.

Common faults of injector assembly (1) Broken of injector assembly fastening stud, the stud is small (generally M10), it may break 122

YUCHAI Engine Service Manual due to stress concentration if being tightened by open-end wrench or spline end wrench (the torque is hard to control) rather than torque wrench. (2) Two situations are involved for jamming of injector matching part: for the first situation, the needle valve is jammed in open position, at this point the fuel cannot be atomized and fully combusted, the engine produces black smoke or white smoke; for the second situation, the needle valve is jammed in close position, at this point this cylinder has no fuel feeding and doesn’t work. No matter which situation it is, the engine power will reduce and accompany with noise. Main causes for jamming of injector matching part are: unclean diesel oil, the needle valve gets jammed by dirt; fuel feeding is abnormal, bad combustion, injector nozzle is ablated and accumulated with too much carbon deposit; oversized fuel feeding angle and high fuel feeding rate, which will result in long-time combustion and high engine temperature. 8.

Burning of cylinder (cover) gasket: the fault is manifested in delaminating of cylinder gasket fire-protection ring sheetmetal and burning of its stuffing (steel gasket is free of this phenomenon), which will damage the gasket and result in gas carry-over problem (to outside or water channel) and water leakage (external leakage or internal leakage to cylinder sleeve) of cylinder cover. Main causes: poor combustion and bad heat dissipation, which will result in high engine temperature; cylinder cover bolts are not fully or evenly tightened, which will enlarge cylinder gasket heating surface and lengthen heating time; oversized valve clearance, high exhaust temperature and oversized fuel feeding angle are also causes of cylinder gasket burning. When gas carry-over phenomenon occurs, abnormal sound will be produced and engine power will reduce.

ATTENTION (1) If burning of cylinder (cover) gasket makes the cylinder and water channel communicate with each other, many bubbles will rise from water tank. (2) If a certain cylinder cover gasket is easily to get burnt, you should check whether the protrusion of cylinder cover locating sleeve meets the requirements, meanwhile, when tightening cylinder cover bolts, you should start from there. So far, no burning of cylinder (cover) gasket caused by deformation of cylinder cover is found.

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313 Assembly Of Water Pump, Fan and Steering Pump 3131 Installation of Water Pump 1.

Structure of water pump: YUCHAI products adopt cooling water pumps, the water pumps have different outside shape, but their inner structure are basically the same, as shown in Fig. 3-111.

Fig. 3-111 Exploded view of YC6105 engine water pump assembly 1 Slotted nut

2 Water pump pulley

3, 4 Bearing

5 Minor circulation pipe

6 Thrower

7 Water seal assembly

8 Carbon seal ring

9 Water pump shaft

10 water pump impeller 14 Bolt

11, 13 Water pump cover gasket

15 Water pump rubber gasket

16 Oil cup

12 Water pump cover 17 Bolt M8×45

Refer to Fig. 3-112 for engine cooling water circulating route

Minor circulation pipe

Engine oil cooler

Cylinder cover

Thermostat

Water pump

Air compressor

Cylinder block Water tank Fig. 3-112 YC6112 engine cooling water circulating route 2.

Common faults of water pump: (1) The most common fault of water pump is water seal leaking water (manifested in water 124

YUCHAI Engine Service Manual dripping from water pump overflow hole). Main causes for damage of water seal are water seal aging failure and longtime no lubricating of water pump. Wear and looseness of water pump bearing will also result in water leakage problem, so when replacing the water seal with a new one, it is better to coat the inner bore of water seal with grease, because the grease not only can play a role of sealing, but also can prevent damage of water seal due to dry friction. (2) Wear of water pump bearing, which can result in sever radial swing of water pump impeller, even colliding with pump body. Wear of water pump bearing is of two kinds: wear of bearing ball is the first kind; and wear of both bearing external circle surface and bearing seat bore. One of the causes is lubricating oil shortage (you should fill grease via the grease nozzle twice a month), the other cause is loose fit between the bearing and bearing seat. (3) Water pump produces abnormal noise: the fault is mainly caused by severely damaged ball bearing which can result in sever radial swing of water pump impeller, even colliding with pump body. If the abnormal noise is friction noise and produced by contacting of water pump shaft and water pump end cover due to oversized axial movement of the shaft, you can eliminate the problem by adjusting the thickness of gasket between water pump end cover and water pump body, refer to part 11 and 13 in Fig. 3-111. When installing the water pump, pay attention apply sealant on the pump gasket and tighten the bolts to required torque.

3132 Installation of Fan 1.

Three kinds of fan are adopted by YUCHAI products, namely steel plate fan, engineering plastic fan and silicone oil fan. Silicone oil fan uses silicone oil to transmit friction force, the silicone oil clutch can aromatically adjust fan rotating speed according to temperature change of hot air from radiator (water tank), and the specific engaging and separating operation is performed by the metal inductor, as shown in Fig. 3-113. Advantages of silicone oil fan: automatically control the engine to keep it working at optimal temperature, reduce fan power consumption, low noise and save energy. Working principle of silicone oil fan: when starting or the temperature is low, there is no silicone oil around the driving plate, the transmission shaft runs idly; when the temperature rises, the metal inductor will swell to turn the switch valve plate for a certain angle to open the oil outlet port, silicone oil will fill up the area between the driving plate and driven plate, and driven plate will be driven by silicone oil friction, thus the fan can rotate. Rotating speed of fan 125

YUCHAI Engine Service Manual is controlled by the metal inductor. Driven disc Fan

Oil return hole

Driven plate

Transmission shaft

Return oil

Silicone oil chamber Switch valve plate Metal inductor

Outlet oil

Hot air

Outlet oil

Connecting bolt

Driving plate

Fig. 3-113 Silicone oil fan working principle diagram 2.

Common faults of silicone oil fan: the automatic control failure, which is mainly caused by metal inductor failure and or leakage of silicone oil. During normal use, please pay attention to clean away the oil dirt and sundries on the metal inductor. The silicone oil clutch has been properly adjusted before delivery, do not disassemble it casually.

TIPS Simple method to determine whether the silicone oil is in good condition: cold-start the engine idly for several minutes, and then shut down the engine immediately, stir the fan blades by hand and should feel easy and flexible, because at this point the silicone oil around driving plate has been thrown back to silicone oil chamber; start the engine again and continue to heat it, and then shut down the engine, stir the fan blades again and you should feel heavy, because at this point, the temperature is high and the area between driving plate and driven plate has been filled up with silicone oil, in this case you have to overcome the silicone oil friction to rotate the fan, which also indicates that the fan is in good condition. Outside shape and installing condition of fan have great effect on engine temperature, hence structural shape and dimensions of fan must conform to its design requirements, and a deformed fan mustn’t be reused. A fan with poor dynamic balance will produce excessive vibration during working and provide bad cooling effect, so when installing radiator and fan cover, you must reasonably fit them with the fan to improve cooling performance. 126

YUCHAI Engine Service Manual

3133 Installation of Steering Pump Most YUCHAI products have adopted rotor pump as steering pump, while vane pump is not excluded, as shown in Fig. 3-114.

Fig. 3-114 Vane pump structural diagram 1 Pump body

2 Pump shaft

7 Stator

8 Rear oil distribution disc

11 O-ring 65×2.65

3 Front oil distribution disc

12 O-ring 67×2.65

15 Oil seal FB16×30×7B 1.

4 Valve

5 Rotor

6 Vane

9 Combination gasket

10 Rear cover

13 O-ring 21.2×1.8

14 O-ring 63×2.65

16 Bearing180203

17 Retainer ring

Cleaning (the steering pump must be cleaned after longtime use): dismantle the flow steady valve and safety valve when cleaning, flush the inner cavity of steering pump, flow steady valve and safety valve with diesel oil. Note that the seal rings and adjusting gasket mustn’t be lost and damaged in this process. When recovering the steering pump (pump blade cambered surface be outward), it is unnecessary to adjust the steady flow valve spring and safety valve spring, if you think the steering pump is abnormal and must be readjusted, you can add gasket to decrease pressure or subtract gasket to increase pressure.

2.

Installation of steering pump Two situations for installation of steering pump: for the first situation, the steering pump is directly installed on rear end of air compressor and driven by air compressor shaft; for the second situation, the steering pump is installed on gear housing cover plate and driven by gear 127

YUCHAI Engine Service Manual in gear housing. 3.

Common faults of steering pump (1) Premature wear of steering pump rotor, stator and front and rear oil distribution disc. The oil used by steering pump is anti-wear hydraulic oil, if the oil is inferior or the oil seal (part 15 in Fig. 3-114) is damaged, too much dirty engine oil will flow into steering pump and result in premature wear. (2) Low oil pressure of steering pump and steering heavy. Under the circumstance of normal oil supplying and abrasion, main cause for this fault is: steady flow valve spring and safety valve spring get softened or inflexible due to longtime no cleaning, which will result in untimely oil discharge and pressure reduce. The solution is to clean the valve springs or add gaskets on upper end of the spring. (3) Hydraulic oil level in steering pump oil tank increases, while engine oil reduces. The main cause is aging and damage of steering pump oil seal (part 15 in Fig. 3-114), which turns the steering pump into a “engine pump”, engine oil is absorbed into the steering pump oil tank through the damaged oil seal.

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YUCHAI Engine Service Manual

314 Assembly of A/C Generator and Starter Motor 3141 A/C Generator Two kinds of generators are used by YUCHAI products, namely exciting generator and permanent magnet generator, refer to Fig. 3-115 and Fig. 3-116 for their principles, power range 0.75KW~3KW. Compared to exciting generator, permanent magnet generator has the advantages of compact size, light weight and excellent low-speed performance (low speed charging voltage is relatively higher). But it also has disadvantages, the “permanent magnet” is actually not permanent, especially after bumping and knocking, the magnetic field can be easily weakened. Hence, after longtime use, the charging voltage of permanent magnet generator will reduce.

Voltage regulator

Fig. 3-115 Principle of brushless exciting generator 1 Generator shell

2 Magnetic field rectifier diode

4 Neutral point rectifier diode

5 Stator winding

D+ Charging indicator lamp terminal W Rotating speed terminal

3 Output rectifier diode 6 Field winding B+ Armature terminal N Neutral point terminal

〨 Ground wire terminal

Fig. 3-116 Principle of brushless permanent magnet generator 1 Generator shell

2 Positive diode

3 SCR 129

4 Stator winding

YUCHAI Engine Service Manual Common faults of A/C generator and troubleshooting: Generator faults mainly focused on three points: open circuit or short circuit of exciting coil (exciting generator); open circuit or short circuit of stator coil (electric output winding); burning of rectifier voltage stabilizing diode or SCR. More specifically: 1.

Generator fails to charge the battery Generator charging failure can be determined by using an ampere meter, so the first thing you need to do is to choose a qualified ampere meter. Two causes may result in generator charging failure (the ampere meter indicates no charging current): generator fails to generate electricity is the first cause; generator can generate electricity but fails to charge the battery due to regulator or circuit failure. So when troubleshooting, you should firstly check whether the generator can generate electricity normally, inspection method: disconnect terminal B+ wiring, start the engine and run it at intermediate speed, set the multimeter to DCV and connect the red probe to generator B+ terminal (positive), ground the black probe (generator shell), at this point if the multimeter indicates voltage reading and the reading keeps going up as engine speed increasing, then it means that the generator is in good condition and the charging failure must be caused by regulator or circuit failure. Another simple inspection method: disconnect terminal B+ wiring, connect a bulb between generator B+ terminal and generator shell, start the engine and run it at intermediate (or higher) speed, if the bulb doesn’t get lightened, then it must be generator failure (fail to generate electricity). For exciting generator, an experienced serviceman can use a wire to instantaneously short-circuit the regulator red wire (positive) and regulator F terminal, if the pointer of ampere meter swings at this point, the regulator must be in failure; if the ampere meter indicates no current, then the charging failure must be caused by ampere meter or circuit failure. After finding out the cause, you need check related parts one by one:

Fig. 3-117 Inspection of open circuit or short circuit of exciting coil 

Refer to Fig. 3-117 for inspection of open circuit or short circuit of exciting coil, if the 130

YUCHAI Engine Service Manual measured resistance value is large, it indicates coil open circuit; if the measured resistance value is small, it indicates interturn short circuit. (Refer to generator instruction manual for standard resistance value). 

Inspection of open circuit and short circuit of armature coil, refer to Fig. 3-115. Disconnect generator terminal N wiring, use a multimeter to measure the resistance between generator terminal N and rectifier diode positive (on generator end cover) for three times, if the three measured values have no big difference, then it indicates that the armature is normal; it is short circuit if the resistance is very large; and it is short circuit if the resistance is much smaller than specified value.



Refer to Fig. 3-118 for inspection of open circuit of rectifier diode Ohms range, about 800,000Ω

Ohms range, about 8Ω

Red Black

Black

Red

Component Diode

Fig. 3-118 Inspection of rectifier diode 2.

Low charging current The so-called low charging current is that the ampere meter indicates 5A or under when engine is running at intermediate speed. One of the causes for low charging voltage is undersized voltage limiting value of regulator, currently all used regulators are nonadjustable, and you have to replace it to do the troubleshooting. The second cause is partial short-circuit in exciting coil or stator winding. The third cause is open circuit of diode. The fourth cause is demagnetization of the permanent magnet. The fifth cause is bad contact.

TIPS High charging current is generally caused by oversized voltage/current limiting value of regulator or damaged diode (damaged diode will result in uncontrollable output voltage). 3.

Unstable charging current (the charging current is sometimes big, sometimes small) Disconnect the wire between battery and regulator, set the multimeter to DCV and connect the red probe armature terminal and ground the black probe. Then increase the engine speed from 131

YUCHAI Engine Service Manual idle speed to intermediate speed, if the charging voltage is stable, then the fault must be caused by faulty regulator or loose terminal; if the charging voltage is unstable, then the fault is caused by generator failure.

3142 Starter Motor Power of selected starter motor for different engine models are different, refer to Fig. 3-119 for its working principle. Common faults of starter motor and troubleshooting: Turn on starter switch, starter motor fails to drive and start the engine. Cause analysis: 1.

Check whether the battery has enough power, turn on front lamps, the battery power is enough if lamp is bright enough. Check the electromagnetic switch: refer to Fig. 3-119. Short-circuit the starter motor terminal 3 and terminal 1, and then check for the following situations: (1) The moveable iron can be absorbed in by big extraction force and produces sound of “de-de”, then it means the electromagnetic switch is in good condition, the starter switch may be faulty. Terminal 3 Starter switch

Return spring Contact disc Pull in winding Holding coil

Power switch

2.

Moveable iron Terminal 1 Terminal 2

Rod

Terminal 4 Field coil Rectiblock

Starter gear

Carbon brush

Starter motor shell

Stop nut Return spring

Battery Electromagnetic coil

Flywheel

Fig. 3-119 Working principle of starter motor (2) The moveable iron cannot be absorbed in, short-circuit terminal 2 (connect terminal 2 to starter motor shell to ground it) at this point, if the moveable iron can be absorbed in, then it means starter motor interior fault, the pull in winding fails to work due to no power supply; if the moveable iron still cannot be absorbed in, then there must be open circuit or short circuit of pull in winding and holding coil in electromagnetic switch. (3) The moveable iron can be absorbed in but bounces back soon, which indicates open circuit 132

YUCHAI Engine Service Manual or short circuit of holding coil. (4) The moveable iron can be absorbed in but the starter motor doesn’t rotate, short-circuit terminal 1 and terminal 2 at this moment, if the starter motor can rotate, then it means the fault is caused by the contact disc, the terminals on contact disc that connected with terminal 1 and terminal 2 are burnt and fail to conduct electricity; if after the moveable iron bounces back the starter motor continues to rotate idly, then it means the contact disc and terminal 1, terminal 2 are sintering together (at this point, you have to turn off the main power or knock terminal 1 and terminal 2 to stop the motor). (5) The moveable iron can be absorbed in but cannot bounce back automatically: 

Starter switch is sintering and cannot be separated (turn off the main power to solve the problem).



The electromagnetic switch moveable iron is inflexible due to corrosion or the return spring is burnt and gets softened (knock the pull in winding to solve the problem).



When turning on the main power switch, the starter motor starts to rotate without turning on the starter switch, and stops rotating as soon as the main power is turned off. This is caused by short circuit of pull in winding terminal and terminal 1 (internal contact). At this point, you just need to loosen fastening nut of terminal 1, press terminal 1 and pull it out to solve the problem, fasten the nut.

3.

Inspection of starter motor Instantaneously short-circuit the terminal 1 and terminal 2, and then check for the followings: (1) The motor is in good condition if the rotor can rotate at high speed idly. (2) No spark produced when short-circuit the terminals and the motor doesn’t rotate, which indicates interior short circuit of starter motor, mainly caused by loose rotor coil or severe burning of rotor rectiblock. (3) A lot of blue spark produced when short-circuit the terminals and the motor doesn’t rotate, which indicates interior short circuit of starter motor, mainly caused by contact of field coil and motor shell, short circuit of carbon brush bracket, contact of rotor coil and carbon brush bracket. (4) Small spark produced when short-circuit the terminals and the motor doesn’t rotate or rotates slowly, which indicates interturn short circuit in starter motor or bad contact of carbon brush due to burning of rotor rectiblock.

4.

Rotating speed of starter rotor is enough, but the crankshaft couldn’t be driven. This is caused by slipping of starter motor one-way clutch, the tooth surface is damaged and couldn’t engage normally, or stroke of starter gear is small and the gear fails to engage. 133

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315 Assembly of Intake and Exhaust Pipes and Turbocharger 3151 Installation of Intake and Exhaust Pipes Intake and exhaust pipes equipped on YUCHAI products are not the same, some engines adopt unitary structure, and some adopt double-body or triple-body structure. For intake pipe, all YUCHAI engines adopt unitary structure except YC6105QC and YC6108Q. Intake pipes of some engine models are installed with heating device, such as YC4110, YC6108ZLQB, YC6112, YC6L and YC6M engine, the heating device can be used as start aid in winter, it is better to disconnect its power source in summer. For YC4108, YC6105 and YC6108 engine, you should install the water outlet pipe before installing the exhaust pipe. Divides according to structure, some intake and exhaust pipe gaskets are of hybrid type (asbestos plus steel disc), some are of single steel disc type. During assembling, an individual engine should be installed the same gaskets, and in principle, the gasket is disposal and should not be reused once removed. When fastening the bolts, it is required to take two steps to tighten them orderly from middle to two ends. Intake and exhaust pipe connecting flanges are thin-wall part, which should not be tightened with excessive force.

3152 Installation of Turbocharger Engine output power can be effectively improve by applying turbocharger. Currently the turbochargers equipped on YUCHAI products are divided into two types, namely common turbocharger and turbocharger with bypass valve. Fig. 3-120 presents a turbocharger with bypass valve. For a common turbocharger, its charging pressure is directly proportional to engine speed, but engine intake pressure and engine speed cannot be controlled; while for turbocharger with bypass valve, its charging pressure is controlled within the design scope by the bypass valve, which prevents high engine fuel consumption and turbocharger overspeed problem due to oversized cylinder explosion pressure (generally happens to a common turbocharger engine). Meanwhile, a turbocharger with bypass valve can improve diesel engine low-speed performance (control low-speed torque and smoke intensity). Although turbocharger structure is not complex, but technical requirements for turbocharger is very high. Rotating speed of turbocharger can reach to more than 100,000r/min, so requirements regarding its bearing lubrication and dynamic balance are very high, the users must follow all requirements in instruction manual to lengthen service life turbocharger.

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Fig. 3-120 YC6105ZLQ turbocharger assembly 1 Turbocharger

2 Turbocharger oil return pipe

4 Connecting bolt (with exhaust pipe) 5 Oil inlet pipe joint

3 Bolt M8×25 6 Bypass valve

7 Bypass valve adjustment lever 1.

Cleaning of turbocharger Turbocharger is lubricated by engine oil, if the engine oil contains too much carbon granules, turbocharger bearing can be easily burnt by carbon deposit under high working temperature (waste gas heat and heat produced by high speed rotation), result in lubricating film damage, bearing and seal ring damage. It is necessary to clean the turbocharger periodically (clean it during every engine oil replacement). Cleaning method: dismantle the turbocharger and fill diesel oil through the engine oil inlet port, plug up the engine oil return port and shake the turbocharger continuously, finally discharge the diesel oil and clean the turbocharger again.

2.

Inspection of turbocharger (1) Refer to Fig. 3-121 to measure axial clearance and radial clearance of turbocharger rotor shaft, standard value: axial clearance 0.10mm, radial clearance 0.15mm. But during normal, the turbocharger is ok as long as the blades cannot touch the shell. Measure with dial indicator Radial clearance

Axial clearance

Fig. 3-121 Measure axial clearance and radial clearance of turbocharger rotor shaft 135

YUCHAI Engine Service Manual (2) Check two ends of turbocharger for oil leakage, if there is engine oil leakage, then the turbocharger seal ring must be damaged. (3) For a normal turbocharger, the bypass valve adjustment lever can be operated by hand with big strength, otherwise the control valve may be rusted and jammed, check and eliminate the problem. 3.

Installation of turbocharger Fill up the inner cavity of turbocharger with engine oil, rotate the shaft for a few circles to fully lubricate the bearings with engine oil, and then discharge the engine oil and install the exhaust pipe joint, note that the connections between turbocharger and air filter & engine intake pipe must be firm, no short circuit or air leakage is allowed. The connecting gasket between turbocharger and exhaust pipe is heat-resistance gasket, do not replace it with other gasket.

4.

Common faults of turbocharger (1) Burn or severe wear of floating bearing, refer to Fig. 3-122. Under normal conditions, you should feel very easy and flexible when rotating the rotor shaft, otherwise the bearing is burnt and inflexible. If bearing is severely worn, the shaft will shake if raise the rotor shaft by hand. Main causes: firstly, engine oil is inferior or insufficient; secondly, the user failed to follow the requirements in instruction manual to maintain the turbocharger (run the engine idly for 3~5min after starting and before shutting down); thirdly, longtime overload working, which will result in poor heat dissipation and accelerate the wear process. Engine oil Waste gas Oil seal Turbine Rotor shaft Air Impeller Seal ring

Engine oil outlet port

Left-hand thread nut Thrust plate

Bearing

Fig. 3-122 Working principle of turbocharger (2) Turbocharger leaks engine oil: engine oil leaked into intake pipe or turbine exhaust pipe from turbocharger inner cavity. The engine will produce blue smoke if engine oil leaked into intake pipe and engine oil consumption will increase. The exhaust pipe will discharge engine oil if there is too much leaked oil. Main causes: severe wear of turbocharger seal rings (opening of the metal seal should face upward); high engine oil pressure, blockage of turbocharger oil return passage; blockage of turbocharger intake passage, low intake 136

YUCHAI Engine Service Manual pressure; longtime idle running. (3) Turbocharger produces abnormal noise: the noise is produced by sundries on turbocharger intake port bumping or scrapping turbocharger impeller; the noise is produced by vibration of turbocharger due to severe wear of floating bearing or wear of thrust plate; airflow rushing sound will be produced if turbocharger intake passage is partially clogged. (4) Fault caused by bypass valve failure: set pressure of bypass valve has been properly adjusted before delivery, generally the user doesn’t need to adjust it, unless the adjustment lever is deformed for some reason, refer to Fig. 3-120. Extend the adjustment lever to reduce the opening pressure, while shorten it to increase the opening pressure. You must pay attention to engine speed change after the adjustment, if engine speed is too high, be sure to readjust to prevent accidents. 

Bypass valve opens prematurely, intake pressure and intake air flow are reduced, which result in black smoke, high fuel consumption, power reduce (disproportion of oil-gas mixture ratio, poor combustion), and high exhaust temperature.



Bypass valve opens too late, intake pressure is increased, which result in overspeed of engine (engine speed goes up with the increasing of intake air flow). Due to overspeed of turbocharger, the floating bearing is easy to damage and the waste gas contains too much NOx.

(5) Excessive vibration of turbocharger. A turbocharger with poor dynamic balance will produce vibration and excessive noise. When the problem gets more serious, the turbine and impeller may bump against the shell, main causes are: uneven wear of floating bearing, failed to align the balancing marks on turbine, impeller, oil seal and thrust plate to marks on turbine shaft. (6) Precautions for use of turbocharger 

Run the engine idly for 3~5min after starting and before shutting down, because the bearing can be easily damaged if rashly speed up the engine before bearing oil pressure is built up. And if suddenly shut down the engine, engine oil will stop flowing immediately, turbocharger shaft will burn and accumulate carbon deposit due to high temperature.



When installing the turbocharger, or replace the engine oil, or before reuse a turbocharger that has been out of service for long time, it is better to fill engine oil into the oil inlet port of turbocharger and rotate the rotor shaft to fully lubricate the bearings and other components inside.



Idle running time of engine should not exceed 20min, because when idling, pressure in 137

YUCHAI Engine Service Manual turbocharger impeller housing is very low, while engine oil pressure in turbocharger inner cavity is very high, engine oil is easy to leak into impeller housing.

3153 Installation of Thermostat Refer to Fig. 3-123.

Fig. 3-123 Thermostat working principle diagram 1.

Thermostats equipped on YUCHAI engines are listed in table 3-33. In Fig. 3, the left valve element is in open and working state (note that the right valve element is in closed state, minor circulation works). When thermostat is fully open, the small valve is in closed state and minor circulation doesn’t work.

Table 3-33 Thermostats Thermostat model Opening temperature oC Full-open temperature oC

530

630

648

B4400

A7100

A39

150

M3000

76

70

70

70

70

57

81

80

83

78

78

80

80

70

95

92

TIPS Thermostat should be selected based on engine model. 2.

Before installing the turbocharger, you should put it in hot water for inspection, to check and ensure the thermostat can open automatically.

3.

Common faults of thermostat The most common fault is malfunction of thermostat, the malfunction is embodied in two aspects: firstly, the thermostat fails to open at specified temperature; secondly, the thermostat can open normally, but the stroke of minor circulation is insufficient and minor circulation pipe cannot be closed fully, in this case, the circulation of water outlet pipe cannot be controlled, which can result in high engine water temperature. When checking, you should put the 138

YUCHAI Engine Service Manual thermostat in hot water to open it and then place it on thermostat seat immediately, the thermostat is normal if the minor circulation pipe can be fully blocked by the minor circulation valve. Generally, the thermostat should be replaced once malfunctioned. If no new thermostat is available and engine water temperature is high, you can disassemble the thermostat and plug the minor circulation pipe orifice for emergency, otherwise, the water temperature will get higher when there is only minor circulation and no major circulation.

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316 Assembly of Intercooler Currently, there are two kinds of intercoolers equipped on YUCHAI products: wind-air intercooler and water-air intercooler, all engines adopt wind-air intercooler except a few YC6112 engines. Refer to Fig. 3-124 and Fig. 3-125. Intercooler

Intake pipe

Turbocharger Fig. 3-124 Wind-air intercooler

Water container welding line

Fig. 3-125 Water-air intercooler Intercooler is used to lower the temperature of supplied compressed air by turbocharger (temperature of air in turbocharger outlet port is about 15oC), to further increase the intake air density, which is helpful to improve engine performance, intercooler is connected between turbocharger and engine intake manifold, generally installed on front side of water tank. In the middle of wind-air intercooler, there is a row of air pipes and air from turbocharger needs to go through these pipes to get to engine intake manifold; there are plate-fins designed on outside surface of the intercooler to dissipate heat of the air. Water-air intercooler adopts double-layer structure, the inner layer is water pipe, there are plate-fins designed on outside surface of the water to dissipate heat; the outside layer is air chamber, air from turbocharger is cooled here by water. Both wind-air intercooler and water-air intercooler have their advantages and disadvantages, wind-air intercooler is more efficient, but of bigger volume. Common faults of intercooler: casting defects, such as sand hole and crack; loose weld or fake weld of inner pipes, which will result in air leakage or water leakage, if the intercooler leaks air, engine power will reduce significantly, even produce black smoke. If the intercooler leaks water, the water 140

YUCHAI Engine Service Manual tank will bubble. Intercooler pipe is thin-wall part and welding repair is difficult to perform, so generally a pipe with welding defect tends to be replaced. Method to inspect intercooler air chamber rear pipes for air leakage: inflate the intercooler to 0.3MPa via the intake port and put the intercooler into water to check whether there is air bubble coming out.

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317 Assembly of Fuel Filter, Engine Oil Filter, Fuel Cut-off Solenoid Valve and Other Components 3171 Installation of Fuel Filter The fuel filters equipped on YUCHAI products are of different models, but they all adopt the same structure, they are all paprt cartridge rotary type filters. Some engine models adopt single stage fuel filter (such as YC4108 and YC6112), while adopt two-state fuel filter. Some filters are disposal, while some are not (the filter cartridge is replaceable), refer to related instruction manuals for details. Common faults of fuel filter: the shell has sand hole defect, the seal ring installed between filter cap and shell is distorted and deformed and result in diesel oil leakage; the user failed to follow the requirements in instruction manual to maintain the filter and result in damage or blockage of filter element, the filter element should be replaced every 20,000kM of driving. Table 3-34 Engine filter models Engine YC6112 YC4112 YC6105 YC6108 YC4108 YC4110 YC6L YC6M model Engine oil JX0811 L3000M3000J91023 J91023 CX0818 JS0818 filter model JX1011 1012020 10122210 Fuel filter 2CX0710 RqCov 2CX0710 CX0708 G4600150CLQ15 CX0710 model CX1011 P60S-2U CX1011 2CX0710 1105410 110502013

3172 Installation of Engine Oil Filter The engine oil filters equipped on YUCHAI products are of different models, but they all adopt the same structure, they are all paprt cartridge rotary type filters. Most engine models only installed with one engine oil filter, directly installed on oil outlet pipe of engine oil pump, only a few engine models installed with two engine oil filters (such as YC6112),. Some filters are disposal, while some are not (the filter cartridge is replaceable). Engine oil filter is designed with bypass valve installed on the filter cap or filter bottom. When filtering resistance exceeds the specified value (about 0.12MPa) due to blockage or other reasons, the bypass valve will open automatically to divert engine oil into main oil gallery directly rather than through the filter cartridge, in order to meet the requirements of lubrication. For non-disposal filter, please be sure to clean the bypass valve every time you replace the filter cartridge. Some filter is installed with engine oil pressure regulating valve on the cap, refer to part 4 in Fig. 3-126, screw-in the adjusting bolt to increase main oil gallery oil pressure, while screw-out to reduce.

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Fig. 3-126 YC4112 engine oil filter assembly 1 Sealing gasket

2 Filter pad

3 Filter gasket

4 Pressure regulating valve assembly

5 Bolt M10×50

6 Filter seat

7 Oil return bolt

8 Paprt cartridge oil discharge pipe

Common faults of engine oil filter: oil leakage or short circuit of oil passage caused by damaged filter gasket 3, result in main gallery oil pressure reduce; main gallery oil pressure reduce caused by blockage of pressure regulating valve or damaged pressure regulating valve seal ring; the user failed to follow the requirements in instruction manual to maintain the filter and result in damage or blockage of filter element.

3173 Installation of Fuel Cut-off Solenoid Valve Refer to part 12 in Fig. 3-75. Fuel cut-off solenoid valve is installed on fuel injection pump flow control handle, when starting switch is turned on for starting or running the engine, the control handle is lock in fuel feeding position by the solenoid valve plunger; when the starting switch is in OFF position, the solenoid valve is out of power and the control handle will reset to stop feeding fuel. Fuel cut-off solenoid valve is inside-packed type vulnerable part, the most common fault is burning of inside coil.

3174 Installation of Other Components Install the cylinder cover shields, high/low pressure fuel pipes, air filter, driving wheels and all kinds of sensors orderly according to requirements in instruction manual.

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4 Inspection & Debugging After the assembling process is finished, the next works we should do are to inspect, run-in and debug the complete engine. These works are very important and special attention should be paid.

41 Inspect Engine Parts and Components for Intactness and Fastening Condition 1.

Lubrication system 1) Retighten the oil drain plug on oil sump. 2) Check whether the engine oil pipe joints, connecting bolts between engine oil filter and engine block, engine oil filter drain screw, air compressor engine oil inlet joint, engine oil cooler inlet and outlet joints, oil inlet and outlet joints of high pressure oil pump and turbocharger are tightened and properly sealed. Check whether oil in engine oil sump is sufficient (use the oil dipstick). 3) Check whether engine oil filter is fully filled with engine oil.

2.

Cooling system 1) Recheck the tensioning degree of fan belt, check whether the water pipes are firmly connected. 2) Check whether matching of water pipes and fan cover meet the requirements. 3) If the engine is designed with expansion water tank, special attention must be paid when assembling the breather pipe on water tank to avoid backwater phenomenon.

3.

Check the turbocharger for infiltration of foreign matters.

4.

Check the air filter and intake pipe for infiltration of foreign matters, check the pipe joints for air short circuit.

5.

Bleed the air in fuel system out by using the hand pump, check the fuel pipelines for air leakage and oil leakage (check by operating the pump).

6.

Check the engine under pan for interference with other parts, eliminate the problem timely.

7.

Recheck and tighten pulley damper fastening nuts.

8.

Check whether the fuel pump handle is flexible, do not start the engine if not.

9.

Check the coaxiality of connection between engine and construction machinery, farm machinery and A/C generator, check whether the vibration isolation equipment is reasonable 144

YUCHAI Engine Service Manual and reliable.

ATTENTION When starting the engine for the first time, it is better to close the throttle and just run the starter motor idly to check whether there is abnormal noise produced by the engine, to avoid after-starting failure caused by potential quality hazard. Besides, do not install the air filter when starting the engine for the first time, so as to plug the intake pipe and stop the engine in case of accident.

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42 Inspection of New Engine A newly assembled engine must be inspected and tested before use, inspection items are “three leakages”, abnormal noise and measuring of relevant technical index. For newly assembled engine without running-in, real contact area of each kinematic pair is still 1/100~1/1000 design contact area, that is, directly run the engine with rated load without running-in can wear and damage the kinematic pair severely. Therefore, a proper run-in period is indispensable. The run-in process can be performed directly on the vehicle or on a testbed. Run-in is divided into three types: the first type is cold run-in, the engine should be driven by prime motor in this process; the second type is no-load hot run-in, the engine should be running idly in this process; the third type is on-load hot run-in, the engine should be loaded gradually in this process. If the run-in is performed on vehicle, cold run-in is not available. If the run-in is performed on a testbed, the starting rotating speed should be 20~25% rated speed; if the run-in is performed on road, the starting rotating speed should be 40~55% rated speed; rotating speed for no-load hot run-in should be 40~55% rated speed; for on-load hot run-in, the starting rotating speed should be 40~50% rated speed, final rotating speed should be 80-100% rated speed, starting load should be 10~20% rated power, and final load should be 80~100% rated power. As to run-in time, it varies in engine models. Generally, 30min for cold run-in (with speed change), 3min for no-load hot run-in and 27min for on-load hot run-in. If the run-in is performed on vehicle, it’s better to drive the vehicle at medium or lower speed without load for the first 60min, and then travel the vehicle at 65% maximum speed and 70% rated load in the following 500km, travel the vehicle at full speed and rated load after 1500km. Inspection of the complete engine (at idle speed, medium speed and high speed): 1.

Oil leakage Respectively check the oil sump, cylinder cover shield, gear housing, fitting surface between engine oil filter and engine block, front and rear oil seals of crankshaft, engine oil cooler and air compressor connecting pipes for engine oil leakage. Check the fuel injection pump, fuel filter and fuel pipe joints for diesel oil leakage. Pay special attention to high pressure fuel pipes and injector fuel return pipes, no oil leakage is allowed in these points in case of fire hazard.

2.

Water leakage Check the engine for water leakage, especially leakage problem inside the engine. Run the engine for about 10min, pull out the engine oil dipstick for inspection, if there is water drops on the dipstick or the engine oil is turned white; or shutdown the engine and remove the oil sump 146

YUCHAI Engine Service Manual drain plug, if the engine oil is turned white (mixed with water), then there must be water leakage problem, find out and cause and eliminate it. 3.

Air leakage Mainly check air cylinders for gas carry-over, check whether is bubble coming out from water tank, check air compressor air inlet and outlet pipe joints for air leakage. Check each joint of turbocharger and intercooler for air leakage.

4.

Water temperature When test-run the engine, the specified valve of water temperature is just for reference, and cannot be used as basis to judge whether engine water temperature is normal. Because when test engine on testbed, the water in water tank is circulating water and the engine is not affected by wind speed; when test engine on vehicle, the engine is temporary not fully loaded, so the measured water temperature is unrepresentative. Therefore, when estimating engine water temperature, you should keep the engine under 70% rated load, engine water temperature is normal if it increases as engine speed increase, but without exceeding 90oC; in addition, comparison method (compared to other normal engines) can also be used to inspect engine water temperature, the engine is abnormal if its water temperature rises quickly. Engine overheating is mainly caused by blockage of water passages in cylinder cover. Real engine water temperature can only be measured when engine works normally.

5.

Engine oil pressure Engine oil pressure must be measured when engine is running normally. The pressure should be more than 0.1MPa (0.3MPa for YC6M engine) at idle speed, as engine speed increases, engine oil pressure goes up stably too. The pressure should be width 0.25~0.6MPa (0.3~0.6MPa for YC6M engine) at high engine speed, if there is big difference between measured value and required value, you must find out the cause and eliminate it.

6.

Inflation pressure When engine is running at medium/high speed, air compressor working pressure should reach above 0.6MPa in 5min, but not exceed 0.8MPa. Air compressor exhaust temperature should be lower than 200oC, if the air compressor cylinder cover is too, be sure to find out the cause and eliminate it. The leakage should not exceed 6.9kPa/min, if pressure loss is too serious (0.069km/cm2), be sure to find out the cause and eliminate it.

7.

Charging current Normal charging current is about 15A when engine is running at medium/high speed, the limit value is controlled by regulator. For a battery with sufficient electricity, it is normal if charging current drops to below 5A gradually 1 hour later. 147

YUCHAI Engine Service Manual For a new battery with adjustable regulator, it is better to adjust the limit value to about 8A, to ensure battery service life. 8.

Run the engine at idle speed, medium speed and high speed respectively to check the color of exhaust gas.

9.

Check whether there is abnormal noise produced by the engine For engine that matched with construction machinery, farm machinery and generator module, the connection in engine output end has special requirements, so the generation of abnormal noise is complex, for instance, the noise may be produced by improper connection, vibration and interference between parts, the users should pay special attention to this.

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43 Testing of Engine Technical Indexes Perform bench testing after the assembled engine passing the inspection. Testing steps are as follows: Step 1: Start and run the engine idly for 3min, check the engine for oil leakage, water leakage and air leakage, eliminate the trouble immediately. Step 2: Hot run-in the engine for 30min. The run-in parameters (speed and time) should be selected based on engine model, please consult the manufacturer for help. Step 3: Carry out performance testing, the performance parameters vary in engine models, parameters in the attached instruction manual are only for reference. 1.

Test condition (1) After the hot run-in period, check and ensure engine oil temperature, engine oil pressure, outlet water temperature and exhaust gas temperature meet related requirements, and perform the test after engine gets stabilized. (2) Keep generator and air compressor unloaded, ensure steering pump is off work, fan and air compressor are not driven. (3) Exhaust backpressure is no bigger than 10kPa.

2.

Test under rated working condition Measure the following parameters when engine is running stably at rated speed and output rated power, refer to related manuals or consult the manufacturer for standard values. (1) Rated power (2) Rated rotating speed (3) Rated fuel consumption (for reference) (4) Intake pressure (5) Exhaust temperature (after turbine) (6) Engine oil temperature (oil sump) (7) Engine oil pressure (8) Piston air leakage (9) Inlet water temperature (10) Cooling water outlet temperature (11) Atmospheric pressure (dry) (12) FSN under full load (13) Free accelerating smoke FSN Perform the next step if all tests under rated working condition have been passed.

3.

Test under maximum torque condition (1) Maximum torque (2) Rotating speed at maximum torque (3) Fuel consumption at maximum torque (4) Intake pressure (5) Exhaust temperature (after turbine) (6) Engine oil temperature (oil sump) (7) Engine oil pressure (8) Cooling water outlet temperature (9) FSN at maximum torque

4.

Other performance tests (1) Torque at 1000r/min (2) Smoke intensity at 1000r/min (3) Torque when add 150Nm load at 149

YUCHAI Engine Service Manual idle speed (4) Rotating speed when add 150Nm load at idle speed (5) FSN under full load (6) Free accelerating smoke FSN

TIPS Parameter requirements can be met by adjusting or replacing parts.

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5 Diagnosis and Elimination of Engine Common Faults Quality of diesel engine mainly depends on three aspects: first, quality of product itself (performance and reliability); second, whether the use and maintenance performed by the user met related requirements in instruction manual; third, whether the service job performed by the serviceman reached each term specification of the product. If any of the three aspects appeared problems, the engine can be adversely affected. This chapter provides service technologies and troubleshooting methods for user and serviceman to refer to.

51 Diagnosis and Analysis of Engine Faults Fault sources 1.

Natural fault: fault caused by engine own quality problem other than improper maintenance or service, such as water leakage or oil leakage caused by sand holes on engine block, wear and out-of-tolerance of crankshaft due to longtime use.

2.

Human initiated fault: the user failed to follow the requirements in instruction manual to maintain the engine and result in failure, or failure caused by service error.

Fault information sources Ask the user for the following information: 1.

Whether it is a sudden fault or a gradual fault? Such as low engine oil pressure. If the acquired information indicates that the oil pressure is low when the engine is new (lower at present), then the fault is generally caused by low fuel supply pressure of engine oil pump (misadjusting of engine oil pump safety valve) or improper adjusting of engine oil pressure regulating valve. If the acquired information indicates that the oil pressure is normal when the engine is new and the pressure reduce is caused by longtime use, then the fault is generally caused by wear of engine oil pump, oil supply shortage, severe engine oil leakage due to excessive wear of kinematic pair blockage of engine oil gallery. If the acquired information indicates that the oil pressure is reduced in a sudden, then the fault is generally caused by damage of parts, such as damage of pump sealing gasket, blockage of oil absorption disc by dirt, sudden damage of bearing or breakage of oil pipes. 151

YUCHAI Engine Service Manual Consult the user or serviceman for operation, maintenance and service situation of the engine: 1.

Change of engine oil pressure and water temperature: when did the change happen? What phenomenon happened? Was it happened before or after the service?

2.

What happened to the oil (engine oil, diesel oil) and water?

3.

What kind of maintenance, adjusting or part replacement is performed on what day, in where, by whom?

4.

When did the engine start to produce abnormal noise or smoke?

5.

What wrong with engine power and speed?

Determine whether it is natural fault or human initiated fault through the work above. Observe the engine on site: 1.

Observe the engine for oil leakage, water leakage and air leakage and find out the cause (insufficient tightening torque, damage of sealing gasket or part).

2.

Listen carefully for noise pattern and position, to identify fault source.

3.

Observe the engine smoke color, find out the cause and eliminate the problem.

4.

Check engine speed change condition to determine whether the engine is in good condition, which is helpful for fault judgment. Generally speaking, one or more of the above four phenomena is/are always involved when it comes to engine failure.

Fault analysis Fault analysis contains three aspects: 1.

Check and determine whether the engine fault is really exist, do not assume any failure by suspicion. To do this, you must be familiar with the followings: (1) Be familiar with fitting parameters and technical data of engine parts. They are basis to judge whether the part or component is qualified. (2) Be familiar with engine performance indexes, such as engine rated power, maximum torque and speed, minimum fuel consumption under full load, exhaust temperature and smoke intensity (including smoke color), etc. Test the engine on testbed to determine whether the engine is qualified. (3) Identify the abnormal noise produced by engine, you must be able to separate abnormal noise from normal noise produced by engine. There must be fault exist if the engine produces abnormal noise. (4) Engine speed stability, whether engine speed is stable or not can directly reflect whether the engine is in failure. The instability mainly happens at low speed stage and rarely 152

YUCHAI Engine Service Manual happens at high/medium speed stage. At high/medium speed stage, accelerating failure is the most common problem, unstable engine speed or accelerating failure is by fuel supply system problem. 2.

Analysis and locate the fault, preliminary locate the fault and its seriousness base on the acquired information and on-site inspection, in order to determine the processes and methods for troubleshooting.

3.

Find out the fault cause by disassembling and inspection.

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52 Engine Common Faults 521 Engine is Hard to Start The so-called “engine is hard to start”, is that when ambient temperature is about 5oC, fail to start the engine three times in succession. There are two situations, one is that cold start is difficult, while hot start is not; the other is that cold start is difficult, so is hot start. To differentiate causes of the two situations, firstly you must know what the causes are. 1.

Causes that may result in engine start failure and phenomena (1) Inferior starter motor or battery ——fail to drive the crankshaft to required speed. (2) Ambient temperature (lower than 5oC) ——compressed air in cylinder is hard to reach required temperature, engine works under low temperature and is easy to produce white smoke. (3) Inferior diesel oil (too high water content) ——engine produces white smoke. (4) Bad compression performance of engine cylinder, temperature is hard to rise ——fitting clearance between cylinder sleeve, piston and piston ring is oversized (air ,oil and smoke pumped out from breather, ), valve clearance is too small or valve sealing strip is burnt or accumulated with too much carbon deposit, sealing performance of cylinder gasket is poor (gas carry-over noise). (5) Large resistance of moving parts, which can affect piston speed and result in low compression temperature ——burning of bearing shell or scuffing of cylinder bore (abnormal knocking sound will be produced). (6) There is air in fuel circuit, fuel supplying shortage no fuel supply ——fuel pipe is poorly connected and leaks air (operate the hand pump to deflate the fuel system and a lot of bubbles will come out). (7) Concentration of gas mixture is abnormal ——air intake is insufficient, fuel concentration is too high (air filter or turbocharger failure, oversized valve clearance), bad atomization of fuel injector nozzle (injector failure), result in incomplete combustion and black exhaust. (8) Starting fuel shortage ——jamming of high pressure pump plunger, movement of rack control linkage is not flexible, starting fuel quantity is improperly adjusted (hard to start in any case). (9) Misadjusting of fuel supply advance angle ——the engine will produce black smoke if advance angle is oversized; and engine will produce while smoke (with carbon granules) if advance angle is undersized. 154

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ATTENTION If a newly assembled engine is hard to start, pay special attention to check whether valve timing is correct. Any of the causes above will result in engine hard to start. Therefore, the second situation may be caused by one or more causes of the nine causes listed above; while for the first situation (cold start is difficult, while hot start is not), it indicates that engine is easy to start after temperature goes up, and of the nine causes, causes that affected by temperature are: oversized valve clearance, incorrect valve timing, air intake shortage; excessive wear of cylinder sleeve, piston and piston ring, the fitting clearance will reduce after temperature goes up, which is helpful for starting; bad atomization of fuel injector nozzle (low fuel injection pressure). 2.

Diagnosis of engine start failure, turn on the ignition key and engine may show: (1) Exhaust pipe doesn’t discharge smoke, which indicates that there is no fuel feeding Cause: ①There is air in fuel circuit ②Fuel cut-off valve is not in fuel feeding/supplying position (2) Exhaust pipe discharges white smoke, which indicates there is fuel feeding, but isn’t ignited Cause: ①Cylinder sleeve is infiltrated with water (cylinder sleeve, engine block or engine cylinder cover is cracked) ②Opening pressure of fuel injector is too low, too much supplied fuel ③Fuel feeding advance angle is too small ④Cylinder pressure is low (wear of cylinder block, piston and piston ring, valve closure lax) (3) Exhaust pipe discharges black smoke and produces explosive sound, which indicates there is fuel feeding, but ignition condition is poor. Cause: ①Bad atomization of injector (higher combustion temperature is needed) ②Ambient temperature is too low (lower than 5oC) ③Fuel feeding advance angle is too large ④Intake air shortage ⑤Starting fuel is insufficient or fuel supply circuit is blocked

522 Engine Underpower The so-called engine underpower, is that engine cannot reach rated speed under no load, or engine maximum output torque cannot meet requirements in instruction manual. 155

YUCHAI Engine Service Manual It should be noted here that if engine is not reasonably matched, engine output power will be directly affected. Therefore, before jump to any conclusion, it is better to test the engine on a testbed. While if the engine is installed on vehicle, you can do some comparison to analysis the failure, such as check whether no-load speed is enough, whether the rotating sound is strong and powerful by ear and experience. If you are satisfied with the sound, check whether there is mismatching between engine and its peripheral components: check whether water tank, fan and fan cover are properly installed; check the matched clutch meet related design requirements, whether there is interference between crankshaft output end and transmission box input shaft; check whether the brake and bearings are smooth and flexible; check whether the A/C transmission mechanism and A/C power are reasonable; check whether the exhaust pipes and intake pipes for transition joints, the failure may be caused by too many transition joints or right-angle joints. If the failure still exists after excluding all the external factors listed above, be sure to fully inspect the engine. 1.

Causes that may result in engine underpower and phenomena Inspection method: Firstly, run the engine with and without load, preliminary determine whether there is engine underpower problem by experience. Secondly, decide whether the underpower is caused by engine self-trouble or by external factors listed above. If it is caused by engine self-trouble, you need to make further inspection. Thirdly, talk to the user to know whether it is sudden failure or gradual failure, to narrow down the fault coverage. (1) Causes for gradual engine underpower ①Bad cylinder compression, leakage of gas mixture, insufficient burning explosion pressure ——wear of cylinder piston, cylinder sleeve, piston ring and valve sealing strip, which result in poor sealing performance ②Fuel feeding shortage ——air leakage of fuel pipe joints, blockage of fuel supply pump oil inlet filter screen or fuel filter element (fuel feeding shortage problem happens at high engine speed), worn plunger results in fuel feeding pressure loss ③High engine oil pressure ——too much water scale in water circuit (especially water tank) and result in poor heat dissipation performance. ④Fuel injection pump fail to inject enough fuel for high speed running ——preload force of high speed spring is insufficient and need to be readjusted. ⑤Turbocharger high speed failure ——turbocharger bypass valve set pressure is low (engine speed change is not obvious no matter the turbocharger is used or not used) and the spring preload force need to be readjusted. 156

YUCHAI Engine Service Manual (2) Causes for sudden engine underpower ①Bad cylinder compression, leakage of gas mixture, high concentration of gas mixture and bad combustion ——breakage of piston ring, valve sealing strip is burst apart. ②Cylinder sleeve is infiltrated with water or cannot work normally ——cylinder bore or cylinder sleeve is cracked, cylinder cover water passage is cracked or injector copper bush is damaged and result in water leakage, water from water passage is infiltrated into cylinder bore or cylinder sleeve due to damaged cylinder gasket. When that occurs, the engine will certainly discharge white smoke, even water. Meanwhile, there will be bubbles and oil dirt in water tank. ③Fuel feeding is abnormal a.

Bad atomization of injector nozzle, which is mainly caused by blockage of fuel injector, low fuel opening pressure, oversized fuel feeding angle, long-time overload low-speed high-temperature running, too much carbon deposit, poor heat dissipation, etc. (There will be abnormal noise)

b.

Jamming of fuel injection pump, shortage of fuel feeding.

c.

Breakage of fuel injection pump high speed spring, engine high-speed application point is low, engine speed is hard to raise (for A-type pump, the spring is installed on governor; for P-type pump, the spring is installed in flyweight; for VE-type pump, the spring is called as governing spring)

d.

Breakage of fuel injection pump delivery valve or delivery valve spring, which results in fuel feeding shortage.

e.

Breakage of valve spring, which can affect air intake and exhaust.

④Misadjusting of other components a.

Valve clearance is oversized or undersized, which can affect air intake and exhaust. The valve will produce knocking sound if the clearance is oversized, while sometimes the valve will produce gas carry-over sound if the clearance is undersized.

b.

Fuel supply advance angle is oversized or undersized.

c.

When adjusting fuel pump, rated speed and fuel feeding rate at rated speed, maximum torque and fuel feeding rate at maximum torque are not properly selected, you must check and readjust.

ATTENTION Sometimes severe scuffing of cylinder bore or burning of bearing shell will also reduce 157

YUCHAI Engine Service Manual engine power. 2.

Diagnosis of engine underpower failure Engine power should be measured at normal water temperature and elevations below 2000m. it is normal if there is a certain power reduce when water temperature is about 100oC in the highland area with altitude over 2000m. Diagnosis of engine underpower failure, accelerate the engine and it may show: (1) Exhaust pipe discharges heavy smoke, which indicates that the consumption is poor Cause: ①Bad cylinder compression ——wear of cylinder piston, cylinder sleeve, piston ring (blue smoke), valve closure lax (black smoke) ②Bad atomization of injector ——opening pressure of injector nozzle is low, blockage of fuel injector (black smoke) ③Fuel feeding advance angle is too big ——engine knock (black smoke) ④Fuel feeding advance angle is too small ——more obvious at low engine speed (white smoke) ⑤Cylinder is filled with water ——cylinder sleeve, engine knock or cylinder cover is cracked (white smoke) ⑥Air intake is insufficient ——engine produces black smoke, especially at high speed. (2) Fuel feeding is insufficient at high speed, but normal at low/medium speed Cause: ①Blockage of fuel supply circuit ②Fuel injection pump is improperly adjusted, or fuel is cu-off too early at high engine speed Tips: The failure may also be caused by low set pressure of turbocharger bypass valve (black smoke). (3) Engine can be accelerate to high speed, but engine is powerless and overload capacity is poor, which indicate that injection pump is improperly adjusted and fuel feeding is insufficient at maximum torque point, readjust the pump.

523 Engine Produces Abnormal Noise Engine can produce a lot of noises during working, so are normal noises, while some are not, and it is hard to distinguish them, besides, the noising position is not easy to locate. In order to correctly locate the problem and find out the cause, you must be good at comparison (pay attention to engine noise at ordinary times, compare noises of two engines and be a doing man (handle the problem by yourself as far as possible), and be good at summing up experience. 158

YUCHAI Engine Service Manual Phenomena and causes Engine abnormal noise can be subdivided into three types: 1.

Sudden abnormal noise (1) Jamming of fuel injector nozzle, the noise is coming from cylinder cover, and the noise is always exists no matter the engine is cold or hot. One of the inspection methods is to use injector testbed, the other is to apply cylinder deactivation method: run the engine idly and disconnect the high pressure fuel pipe of each cylinder one by one, the just disconnected injector is jammed if the noise suddenly disappeared. (2) Bumping cylinder base, the noise is coming from cylinder cover. (3) Scuffing of cylinder bore, engine produces strike noise and power is reduced significantly, engine seemed powerless especially at idle speed, even produces black smoke. Breakage of piston ring, poor combustion, bad cooling effect of piston, abnormal working of fuel injector and high engine temperature are main causes for this failure. (4) Dry friction sound produced by air compressor shaft, the failure is mainly caused by blockage of air compressor oil inlet pipe or crack of oil pipe, in this case, the air compressor will be very hot and produce abnormal noise, please shut down the engine for inspection immediately. (5) Turbocharger (if installed) produces strike noise, the noise is mainly caused by bumping of turbocharger impeller and shell due to oversized axial movement or radial movement of turbocharger. If the problem is not serious, the noise may hard to detect when engine is running stably.

2.

Natural gradual abnormal noise (intension of the noise increases gradually) (1) Valve sealing strip is ablated and accumulated with too much carbon deposit, and result in gas carry-over, the noise is coming from cylinder cover. Cause: ① Valve clearance is undersized and result in gas carry-over after engine temperature ②Valve is burnt or accumulated with too much carbon deposit (cylinder is infiltrated with engine oil, bad atomization, poor combustion and high engine temperature) (2) The crankshaft shaft will produce severe strike sound (coming from oil sump) if the main bearing shell or connecting rod bearing shell is worn, the sound is more clear at 10m from the engine. If connecting rod bearing shell is severely worn, there will also be piston-bumping-valve noise (at this point, the valve will vibrate seriously). Wear of bearing shell will also result in engine oil pressure reduce, and when draining engine oil, there must 159

YUCHAI Engine Service Manual be alloy debris on the plug.

ATTENTION Burning of bearing shell is very dangerous, please be sure to shut down the engine for inspection once abnormal noise produced by bearing is detected. (3) Severe wear of piston pin and pin hole and scuffing of cylinder bore by piston or cylinder sleeve will also produce strike sound, but the sound is hard to locate without disassembling. (4) Intermittent strike sound from gear housing due to wear of idle gear shaft and oversized timing gear backlash, the sound is more obvious if engine speed is unstable. (5) Noise form clutch, strike sound will be produced if release bearing is damaged, or if driven plate steel disc or rivet is loose or damaged, the higher the engine speed, the louder the strike sound. If the strike sound gets fainter or disappeared when the clutch is engaged, then the strike sound must come from flywheel shell. 3.

Human initiated abnormal noise (caused by improper installation or adjusting) (1) Abnormal noise caused by oversized valve clearance generally comes from cylinder cover, the noise is more obvious when engine speed is low and temperature is high. If valve clearance is undersized there will be gas carry-over noise, more obvious when engine temperature is high (especially when air filter or exhaust manifold is removed), check the valve clearance to identify the problem. (2) If the fuel injection pump is designed with advance units, each of the advance units will produce sound when engine is working, and the sound may vary in size, note the sound is not abnormal noise and wouldn’t affect the work. Tips: If the fitting clearance between advance unit and hole on injection pump connecting plate is oversized, the sound produced by advance unit will be louder, meanwhile, too large coaxiality error between air compressor shaft and fuel injection pump shaft will also result in loud noise, pay attention to this during inspection. (3) Resonance noise, sometimes there will be resonance noise produced when engine is running at a certain speed (sometimes the engine vibrates together with the whole vehicle), which is caused by chassis structure or engine installation defect, causes for this failure are complex and detailed examination is indispensable. (4) Air shock sound produced by exhaust pipe, which is mainly caused by change of valve timing. Causes: bend or breakage of pushrod, breakage of valve spring; crankshaft timing gear or pulley is displaced due to no locating pin or key and result in abnormal valve timing. 160

YUCHAI Engine Service Manual Method to check valve timing: Rotate the crankshaft until cylinder 1 reaches exhaust 30o BTDC, turn the intake pushrod of cylinder 1 left and right by hand and it should be easy and flexible, continue to rotate the crankshaft until it is a bit tight to turn pushrod. At this point, the reading on the dial is cylinder 1 intake valve open angle, which should meet the requirement in table 5-1. The valve timing is incorrect if the difference is greater than 7o.

Fig. 5-1 Valve timing inspection diagram 1 Pushrod

2 Adjusting screw

3 Intake valve

4 Dial

Table 6-1 Reference values of engine valve timing Engine model YC6112, YC6105, Parameter YC4112 YC6108 Intake valve open angle (°)

13.5

17

YC4108

YC4110

YC6L

YC6M (when intake valve clearance is 1±0.05)

14

14±5

29.5±5

2±5

524 Low Engine Oil Pressure As indicated in instruction manual for YUCHAI products, engine oil pressure at idle speed is 0.1MPa and lower than 0.6Mpa when engine is running at high speed. If engine idle-speed oil pressure is lower than 0.1MPa, or medium/high-speed oil pressure is lower than 0.2Mpa (0.4MPa for YC6M engine), we can determine that engine oil pressure is low. Whether engine is properly lubricated or not can greatly affect engine performance and service life. Engine oil can not only act as anti-friction agent, also it can be used for cooling, cleaning, sealing and anti-rusting. Therefore, only when engine oil pressure is normal can enough engine oil flow be guaranteed for normal working of engine.

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YUCHAI Engine Service Manual 1.

Causes that may result in low engine oil pressure (refer to Fig. 5-2 for YC6112 lubrication route)

YC6112 engine lubrication route Main oil gallery Bypass valve

Idler shaft

Oil cooler

Piston cooling nozzle

Main bearing

Rocker

Piston Connecting rod bearing

Valve

Tappet

Gear train Oil pump

The firstcamshaft bearing sleeve

Injection pump

Oil filter

Air compressor

Turbocharger

Bypass valve

Cam bearing

Connecting rod sleeve

Pressure limiting valve

Engine oil sump

Fig. 5-2 Low engine oil pressure is divided into three types: (1) Gradual pressure reduction——engine oil pressure was normal, and then reduces gradually due to longtime use. Possible causes are as follows: 

Oversized fitting clearance due to gradual wear of related parts, deterioration of engine oil due to longtime use or long-term high-temperature operation.



Engine oil pump inner rotor, outer rotor and end cover are worn, engine oil pump safety valve is inflexible or valve spring is softened.



Blockage of engine oil filter element, especially for engine with severe worn cylinder sleeve and piston, the filter element should be cleaned and replaced periodically.



Blockage of oil strainer screen. Engine oil pressure will show small or no rise when accelerating the engine from idle speed to high speed if oil strainer screen or filter element is blocked. Sometimes the engine oil pressure even reduces as engine speed goes up.



Main bearing shell, connecting rod bearing shell, camshaft sleeve and idler shaft copper bush are worn and result in severe oil leakage.

162

YUCHAI Engine Service Manual (2) Sudden pressure reduction——engine oil pressure reduces in a sudden due to damage of related parts. Possible causes are as follows: 

Engine oil filter gasket is damaged and result in engine oil short circuit.



Engine oil cooler shell (some engine models are free of engine oil cooler) is cracked or loose welded and result in engine oil leakage, in this case, there will be engine oil in water tank.



Perforation or sand hole of main oil gallery (this phenomenon is rare).



Engine oil spray nozzle (plastic part) on main bearing seat is aged, corroded and damaged or spray hook is loose and result in serious oil leakage.



Engine temperature is too high and result in decrease of engine oil viscosity.



Engine oil pump shaft is broken or the shaft sleeve is loose, engine oil pump failure.

(3) Human initiated pressure reduction——caused by improper adjusting or faulty operation. 

Engine oil pressure gauge is faulty, the reading is not correct.



Main oil gallery pressure limiting valve or pressure regulating valve on engine oil filter is under-adjusted or dirty and result in failure. Note that YC6112 and YC6108ZLQB engine is free of this component, but if the safety valve on engine oil pump is under-adjusted or faulty, engine oil pressure will also be affected.



The selected engine oil quality is poor and tends to deteriorate and thin quickly.

ATTENTION Sometimes engine oil pressure may disappear in a sudden, the possible causes: engine oil pump shaft or engine oil pump transmission gear shaft is broken, causing engine oil pump unable to rotate; engine oil filter oil inlet pipe weld assembly is fractured or engine oil pump connecting screws are loose, causing infiltration of air of oil circuit and oil absorption failure. In the case of no detecting instrument, to identify whether there is engine oil pressure, you can remove the cylinder cover shield and check if there is oil surging up from rocker arm oil outlet hole when engine is running idly, there is no engine oil pressure if not.

WARNING When engine oil pressure is lower than 0.08MPa at idle speed or lower than 0.15MPa at medium/high speed, be sure to stop the engine for inspection, do not count on luck.

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YUCHAI Engine Service Manual 2.

Refer to the block diagram below for diagnosis of low engine oil pressure fault. High engine oil temperature fault

Oil pressure is normal when Clean engine oil filter and adjust the pressure limiting valve, and engine is cold; oil pressure is then seal off the oil inlet gallery of air compressor and fuel injection low when engine is hot pump for about 1min, observe main oil gallery pressure change

Piston cooling nozzle is loose

Severe wear of intermediate gear copper bush (abnormal noise from gear housing)

Severe wear of camshaft copper bush, oil supply for rocker is insufficient

Severe wear of bearing shell (abnormal noise)

Engine oil filter is clogged due to deformation

Joint or connector has oil leakage or air leakage porblem

Oil absorption plate is blocked

Engine oil pump is worn and leaking oil

Engine oil quality is poor (too thin)

Engine oil is insufficient 3.

Oil supply from main oil Main oil gallery rear end is gallery front end is insufficient worn and leaking oil if the oil if the oil pressure gets larger pressure barely changes

Causes for burning of bearing shell (1) Low engine oil pressure, even shortage of engine oil 

If the engine oil pressure was reduced gradually, then the bearing shell must be severely worn (thinned), in this case, the bearing shell surface and connecting rod big end may not be burnt blue.



If the engine oil pressure was reduced in a sudden or engine oil is insufficient, in this case, the bearing shell is generally not thinned, but large area of scratch damage and burning damage will occur, and usually the shell surface is not smooth, the bearing shell and connecting rod may be burnt blue.

(2) Poor lubrication caused by undersized or oversized fitting clearance between bearing shell and journal 164

YUCHAI Engine Service Manual 

If fitting clearance is too small, oil film will be hard to form, which will result in direct friction between bearing shell and journal, and easily leading to wear and scratch damage (mostly near the separate surface of bearing shell). This kind of scratch damage can easily result in burning of bearing shell in the first thousands of kilometers if overloaded. If no burning of bearing shell occurred in the first 10,000km, then the shell is safe for now.



If fitting clearance is too big but still within the limit, lubrication action still exists, but the lubrication performance is poor. Meanwhile, bearing shell is more easily to subject to bumping, which will result in deformation and burning of bearing shell. This kind of burning is generally happened after 30,000km, and the bearing shell will be severely worn (thinned), the connecting rod big end may not be burnt blue.

(3) Disqualification of part material. 

Poor material quality. Such as low rigidity of journal, shrinkage of the structure and delamination of bearing shell alloy, which can easily result in wear, scratch and burning of bearing shell. With material like this, the bearing shell may burn at any time regardless of lubrication, and generally there will be obvious scratch damage on the burnt shell.



Poor surface finish. Such as rough journal surface and burr and flashing on bearing shell, tiny scratch strips will appear on the bearing shell in the first thousands of kilometers regardless of lubrication.



Unqualified engine oil. Engine oil viscosity is low, poor lubrication, which will accelerate the wear and burn the bearing shell, in this case, damage condition of all bearing shells are basically the same.



Unclean engine oil, even mixed with sundries. The bearing shell can be scratched at any time.



High engine working temperature, and engine oil tends to deteriorate easily, which will accelerate the wear and burn the bearing shell. Bearing shell will burn severely and may turn blue under such circumstance.

Causes for burning of bearing shell are diverse and complex, so it is not an easy job to find out the cause, you must talk to the user to get know of the fault. ATTENTION: To detect the burning of bearing shell as soon as possible, you must remove the drain plug of oil sump for inspection regularly.

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YUCHAI Engine Service Manual

525 High Engine Water Temperature Engine water temperature can be directly read from temperature gauge, the temperature is high if the reading is bigger than 98oC, or the water in water tank is boiling. High engine water temperature can adversely affect service life of the engine. But if the temperature is too low, heat consumption will significantly increase, fitting clearance between parts will enlarge and the parts will hit against each other; meanwhile, engine oil viscosity is high at low temperature, lubrication performance will be greatly reduced. Abrasion loss of a cold start is nearly equal to that of 50km traveling distance. When cold start, lubrication condition is poor, and minor abrasion damage will be formed between cylinder sleeve and piston, you must run the engine idly for a few minutes after cold start to rubdown the damage, do not accelerate the engine immediately. Normal engine working temperature is 85oC~95oC, in terms of minimum wear, 85oC is best, so keep a reasonable control on engine water temperature is one of the effect methods to improve working efficiency of engine, special attention should be paid to this. 1.

Causes for high engine water temperature (1) Effect of circulating water cooling is poor (including water-cooling and air-cooling) 

There is no enough water in water tank, radiating pipe is deformed and clogged, water passage of engine oil cooler is blocked, too much accumulated water scale in water tank and result in bad heat dissipation performance (touch the top and bottom of water tank with hand and there will be great temperature difference).



Thermostat failure, opening degree of thermostat is not enough, too much water flow in water pump minor circulation pipe (press the pipe with finger and you can feel that the water pressure is high).



Water pump belt is loose or damaged, which results in abnormal rotating speed of water pump.

(2) Bad combustion in cylinder 

Injection pump feeding rate is too high, combustion time is too long (exhaust pipe discharge black smoke)



Fuel supply advance angle is too large, atomization of injector is poor and injector opening pressure is oversized, cylinder combustion condition is severe under such circumstance and engine temperature will rise (knocking phenomenon may occur).



Opening degree of exhaust valve is undersized, heat discharge and exhaust gas discharge is obstructed. 166

YUCHAI Engine Service Manual 

Set value of turbocharger bypass valve high-speed pressure is high, which results in high intake pressure and increase of engine speed.



Cylinder bed bumping or crack of cylinder sleeve, high temperature exhaust gas flows into water passage and result in high water temperature, but real engine temperature may not be high.



Scuffing of air compressor, in this case, air compressor temperature and water temperature are high, but engine temperature is not.

(3) Inappropriate installation and use 

Water tank, fan cover and fan are not reasonably matched (refer to charger 4 for matching requirements).



Check whether heat dissipation of water tank is adversely affected by wrong installation position of turbocharger and intercooler.



Exhaust valve is not reasonably opened (mostly at low speed stage), heat discharge and exhaust gas discharge is obstructed.



Long time overload working.

Diagnosis of high engine water temperature fault

2.

High engine water temperature fault

Water temperature of a new or just repaired engine is high (part or installation fault)

The water temperature was normal, but rises gradually after longtime use

Overload working

Fan is damaged (silicone oil sensor failure)

Bumping cylinder base and cracking of cyinder sleeve (water tank produces bubbles)

Scuffling of cylinder bore (including air compressor)

Fuel injector nozzle is jammed, too long fuel supplying time, exhaust pipe discharges black smoke

Leakage of circulation oil passage

Water pump belt is loose, rotating speed of fan is insufficient Fuel injection pressure is low, too high fuel supplying rate, exhaust pipe discharges black smoke

Thermostat failure

167

Engine oil cooler is accumulated with too much water scale

Water pipe is aged, deformed or blocked

Water tank is accumulated with too much water scale, (temperature difference between up and down is big)

Rotating speed of fan belt or water pump is insufficient

Ventilation around engine is poor

Water tank fan cover and fan are poorly matched

Water tank is too small

Cylinder cover water jacket is blocked

Circulation of air or water cooling is poorly matched

The water temperature was increased in a sudden

YUCHAI Engine Service Manual 3.

Back-water of water tank The so-called back-water of water tank, is that when suddenly accelerating or slow down the engine, water flows out from water tank filling port or expansion water tank filling port. Back-water of water tank can be subdivided into two types, namely with bubbles or without bubbles. Causes of the bubbles: engine cylinder sleeve (cylinder block) or cylinder cover is fractured, or cylinder bed is damaged at the area where water holes is involved, result in infiltration of exhaust gas; the water pipeline from engine water outlet pipe to water tank is poorly sealed. Causes for back-water of water tank: (1) Back-water without bubbles is mainly caused by blockage of water tank radiating pipes, or ageing, deformation or blockage of water pump air intake rubber hose, when accelerating the engine suddenly, water flow from water outlet pipe will be bigger than water inflow of water pump and result in back water of water tank; if the back-water happens when suddenly slow down the engine, then it is mainly caused by undersized opening degree of thermostat. When accelerating, water pump will absorb a lot of water, water pressure in engine block will rise because outlet of thermostat is blocked, slow down the engine at this point, water abortion rate of pump will reduce significantly, high pressure water in water tank will burst into water tank and result in back-water. (2) Back-water with bubbles is mainly caused by unreasonable design of water tank, as shown in Fig. 5-3, if bottom end of water tank filling port is lower than upper plane of water tank inner cavity, an air chamber will be formed. When accelerating the engine, the water level will rise, if the compressed air is not discharged timely, it will coming out from the filling port together with water. The fault is more common when fan heater water circulation connecting pipe has air leakage problem. Compressed air Water filling port Water Air

Fig. 5-3

526 Engine Produces Abnormal Smoke Four situations for abnormal smoke of engine: 

Abnormal smoke is produced only during starting. 168

YUCHAI Engine Service Manual 

Abnormal smoke is produced at medium/low engine speed.



Abnormal smoke is produced regardless of engine speed.



Abnormal smoke is only produced when accelerating suddenly.

Smoke color is subject to working condition of each cylinder, composition of exhaust gas is complex and different composition will result in different color, basically the smoke is divided into three colors, block color, white color (grey white) and blue color (dark blue). 1.

Causes for abnormal engine smoke (1) Black smoke (fuel supplying is vast, incomplete combustion) 

Severe wear of cylinder sleeve, piston and piston ring, valve closure lax, oversized or under sized valve clearance, which result in bad compression.



Air filter or turbocharger failure, leading to insufficient air intake and result in disproportion of gas mixture (rich fuel and poor air content).



The fuel injection pump is improperly adjusted, fuel feeding rate is too big. Misadjusting of injector nozzle and jamming of injector nozzle, bad atomization, and incomplete combustion.



Oversized fuel supply advance angle, fuel is incompletely combusted at low ambient temperature.



Exhaust valve opening degree is too small, exhaust passage is obstructed, which can affect cylinder air intake and exhaust temperature, and bad for normal working of engine.

(2) Blue smoke (burning of engine oil) 

Piston or piston ring is severely worn or piston is fractured, piston ring is broken, which result in engine oil entering into cylinder and burning.



Turbocharger sealing ring is damaged, so that the engine oil enters the combustion chamber along the intake passage and is combusted, when air filter is blocked, the phenomenon is more serious.



Severe wear of valve guide pipe, engine oil enters into cylinder through valve guide pipe and burns.



Fitting clearance between piston ring and ring groove doesn’t meet related requirements, oil from sump is easy to enter into cylinder and burn (a new part can also has this problem)

(3) White smoke (fuel contains too much water, incomplete combustion), more obvious when engine speed is low, smoke color is similar to water vapor. 169

YUCHAI Engine Service Manual 

Cylinder sleeve or engine block and cylinder cover are cracked, injector nozzle copper bush is damaged, water flows into cylinder sleeve directly.



Low ambient temperature, part of the fuel is incompletely combusted.



Fuel supply advance angle is too small, some fuel is discharged instead of being combusted.

ATTENTION For engine with fuel preheating device installed on intake pipe, when preheating device (including relay) is in failure, oil in the preheating device will flow into engine intake pipe, which will result in blue/white smoke at idle speed, blue/black smoke at medium/high speed. The smoke intensity decreases as engine speed rises. When troubleshooting, you just need to disconnect the oil inlet pipe and power wire of preheating device, the preheating device is faulty if the smoke intensity decreases. Diagnosis of abnormal engine smoke fault

2.

Diagnosis of abnormal engine smoke fault

Abnormal smoke is produced only during starting

Abnormal smoke is Abnormal smoke is produced produced at medium/low at high engine speed other engine speed than low engine speed

Abnormal smoke is only produced when accelerating suddenly

Preload force of fuel injection pump smoke limiter spring is insufficient and result in oversized fuel feeding rate at low speed stage

Air valve leaks air

Wear of cylinder sleeve (blue smoke)

Undersized fuel supplying advance angle (white smoke)

Turbocharger leaks oil (blue smoke)

Insufficient air intake (black smoke)

Bad compression of air cylinder

Oversized fuel feeding rate (black smoke)

Oversized fuel supplying advance angle (black smoke)

Bad atomization of fuel injector (black smoke)

Turbocharger bypass valve limiting valve is too low and results in insufficient air intake when pressure is high

Wear of pump plunger (at high engine speed, leaked fuel is proportionally less than feed fuel)

Bad atomization of fuel injector (black smoke)

Low ambient temperature (white smoke)

Cylinder sleeve is cracked

Fuel injection pump smoke limiter is in high fuel feeding rate position

Too high starting fuel feeding rate, the pump is improperly adjusted,

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Abnormal smoke is produced regardless of engine speed

YUCHAI Engine Service Manual

527 Vibration of Engine The so-called vibration of engine is that when the engine is installed on vehicle, severe vibration is produced by the whole machine. The vibration is mainly caused by poor dynamic balance of engine itself, unstable engine speed or unreasonable matching of engine and chassis. 1.

Causes for vibration of engine (1) Parts and components that may affect dynamic balance of engine are crankshaft, flywheel, clutch and belt pulley (damper plate), these parts and components have passed dynamic balancing testing before delivery. Piston connecting rods have been used in pair by weight when assembling. If the engine was normal at first, then the vibration is not caused by the parts and components mentioned above. (2) Unstable engine speed will also result in vibration, and vibration caused by unstable idle speed is the most common one, the fuel injection pump idle working point is incorrectly adjusted in this case, and increase the idle speed can temporarily solve the problem. If engine speed is unstable at medium/high speed stage, the vehicle will show creeping phenomenon, which is mainly caused by misadjusting or poor quality of high-speed spring, replace the governor if necessary. (3) Unreasonable matching of engine and chassis Whether the matching of engine and chassis is reasonable can greatly affect engine balancing, so when installing the engine, the four engine legs must fall on the four holders of chassis simultaneously, otherwise, vibration of engine and chassis will occur (resonance may occur at a certain engine speed).

2.

Diagnosis of engine resonance Firstly, you must make sure if the vibration is caused by unstable engine speed, adjust or replace the pump to stabilize the engine if so. Secondly, ask the user to know when did the vibration started, if it started just after assembled, you should take down the engine and put it on level floor for inspection, the engine is faulty if the vibration is still obvious; if the vibration is disappeared, then the vibration must be caused by unreasonable matching of engine and chassis. If the vibration started after a period of use, and none the dynamic balance related parts and components is repaired, then the vibration must be caused by deformation of chassis or loose connections.

ATTENTION If the vehicle is installed with A/C, interference of A/C will also result in engine vibration, find out the cause and pay attention to it. 171

YUCHAI Engine Service Manual

53 Emergency Handling Methods for Engine Common Faults Various faults may happen at any time when using engine, for most faults, you have to shut down the engine for repairing. And for some faults, repair it at that moment that place may not be available and short-term running is needed, make appropriate treatment on the fault and you can continue to use the engine for emergency. 1.

Piston, cylinder sleeve or connecting rod bearing of a certain cylinder is burnt or damaged. You can remove the piston connecting rod assembly of this cylinder and block the oil ducts of the connecting rod journal with cloth strips to prevent engine oil leakage and pressure reduction. Meanwhile, you should disconnect the high pressure fuel pipe of this cylinder and unload the fuel delivery spring, and then plug the fuel delivery joint for temporary use. Do not run the engine at high speed under such circumstance to prevent large vibration.

2.

Engine oil pressure gauge or oil sensor couldn’t reflect real pressure. At this point, you can remove the cylinder cover shield and check if there is oil surging up from rocker arm oil outlet hole when engine is running idly, the engine oil pressure is normal if so, but be sure to repair the pressure gauge or sensor timely.

3.

Breakage of high pressure fuel pipe. If there is no available pipe for replacement, you can loosen the fuel delivery valve of this cylinder and plug the fuel delivery joint, or divert the fuel back to fuel tank for temporary use, do not run the engine at high speed under such circumstance.

4.

If engine water temperature is affected by thermostat failure, you can disassemble the thermostat and plug the minor circulation water pipe of thermostat to prevent short circuit and high water temperature.

5.

Fuel injector gets stuck in open position, which can affect engine performance and increase fuel consumption. Handling method: if there is available new injector, you can replace the faulty one with the new one and adjust it; if there is no available new injector you can loosen the fuel delivery valve of this cylinder to stop the fuel feeding.

6.

Damage of fuel cut-off device (on fuel injection pump) or A/C idle-speed riser, which result in no fuel supplying or A/C failure. At this point, you just need to adjust the adjusting screw of fuel cut-off device or A/C idle-speed riser towards fuel-increasing direction.

7.

The engine is installed with silicone oil fan, if engine water temperature is affected by silicone oil clutch failure, you can drill four thread holes on silicone oil clutch shell and engine front cover and connect them with M10 bolts to use the silicone oil fan as common fan. But you must pay attention to that if severe vibration is caused by the modification, be sure to reduce the engine speed as far as possible. 172

YUCHAI Engine Service Manual

6 Engine Parameters 61

Engine Technical Parameters

Table 6-1 YC4108 series engine technical specifications Engine model Parameters Air intake type

YC4108Q Naturally aspirated

YC4108ZQ

YC4108ZLQ

Supercharged

Turbocharged inter-cooled

Cylinder diameter (mm)

108

Piston stroke (mm)

115

Total displacement (L) Rated power (kW)

4.214 75

90

84.5

Rated speed (r/min) Maximum torque (Nm) Speed at maximum torque (r/min) Maximum no-load speed (r/min)

2800 268

380

380

1600~1900

≤3300

≤3150 700~750

≤225

≤210

≤215

≤3.5

≤3.0

≤2.5

Fire ignition sequence Crankshaft rotation direction

332

1600~1900

Idle speed (r/min) External characteristic minimum fuel consumption (g/kWh) Exhaust smoke intensity (FSN)

96

1-3-4-2 Anticlockwise (View from power output end)

(Static) Fuel injection advance angle (BTDC) (°CA)

13°±2°

173

9°~11°

YUCHAI Engine Service Manual Table 6-2 YC4110 series diesel engine technical specifications Engine model Parameters Air intake type

YC4110Q Naturally aspirated

YC4110ZQ

YC4110ZLQ

Supercharged

Turbocharged inter-cooled

Cylinder diameter (mm)

110

Piston stroke (mm)

112

Total displacement (L)

4.257

Rated power (kW)

80

100

110

Rated speed (r/min)

3000

2800

2600 (2800)

Maximum torque (Nm)

278

392

490 (450)

1900~2200

1600~1800

1400~1700

228

215

215

≤3.8

Euro I

Euro II

Speed at maximum torque (r/min) Full load minimum fuel consumption (g/kWh) Exhaust smoke intensity (FSN) Fire ignition sequence Maximum no-load speed (r/min) (Static) Fuel injection advance angle (BTDC) (°CA) Crankshaft rotation direction

1-3-4-2 ≤3400

≤3150

11°±2°

≤3080 (Rated 2800rpm) ≤2900 (Rated 2600rpm) 8°~10°

Anticlockwise (View from power output end)

174

YUCHAI Engine Service Manual Table 6-3 YC4112 series diesel engine technical specifications Engine model Parameters Air intake type

YC4112ZQ (G0100)

YC4112ZLQ (G0200)

Supercharged

YC4112ZLQ (G0400)

YC4112ZLQ （G0800)

Turbocharged inter-cooled

Cylinder diameter (mm)

112

Piston stroke (mm)

132

Total displacement (L)

5.202

Rated power (kW)

105

125~132

Rated speed (r/min)

2400

Maximum torque (Nm)

500

660

630

660

Speed at maximum torque (r/min) Full load minimum fuel consumption (g/kWh) Exhaust smoke intensity (FSN)

≤1600

≤1500

1400~1600

≤1400

132

2300

≤210

≤205 ≤3.5

Emission standard

Euro I

Euro II

Fire ignition sequence Maximum no-load speed (r/min) Crankshaft rotation direction

125

1-3-4-2 2680~2760

2570~2640

2680~2760

2570~2640

Anticlockwise (View from power output end)

175

YUCHAI Engine Service Manual Table 6-4 YC6105ZQC, YC6108ZQ series diesel engine technical specifications YC6105ZQC YC6108ZQ Engine model Parameters (J3200) (J3300) B3000 B3200 Air intake type

Supercharged

Cylinder diameter (mm)

105

108

Piston stroke (mm)

125

Total displacement (L) Rated power (kW)

6.494 105

6.871 118

Rated speed (r/min) Maximum torque (Nm) Speed at maximum torque (r/min)

132

118

560

190

2600 430 1400~1700

520 1400~1800

Idle speed (r/min)

1500~1800 700~7500

Full load minimum fuel consumption (g/kWh)

≤218

Emission standard

Euro I

Fire ignition sequence (Static) Fuel injection advance angle (BTDC) (°CA) Maximum no-load speed (r/min) Crankshaft rotation direction

B3300

1-5-3-6-2-4 9°~13° 2860~2910 Anticlockwise (View from power output end)

176

YUCHAI Engine Service Manual Table 6-5 YC6108ZLQB series diesel engine technical specifications Engine model Parameters

YC6108ZLQB (A3200)

YC6108ZLQB (A3500)

Air intake type

YC6108ZLQB (A3100)

Turbocharged inter-cooled

Cylinder diameter (mm)

108

Piston stroke (mm)

132

Total displacement (L)

7.255

Rated power (kW)

177

191

Rated speed (r/min) Maximum torque (Nm) Speed at maximum torque (r/min) Full load minimum fuel consumption (g/kWh) Exhaust smoke intensity (FSN)

YC6108ZLQB (A4400)

2300 860

950 1400~1600 210

3.0

2.5

3.0

2.5

Emission standard

Euro I

Euro II

Euro I

Euro II

(Static) Fuel injection advance angle (BTDC) (°CA)

9°~11°

7°~9°

9°~11°

7°~9°

Fire ignition sequence Crankshaft rotation

1-5-3-6-2-4 Anticlockwise (View from power output end)

177

YUCHAI Engine Service Manual Table 6-6 YC6112 series diesel engine technical specifications Engine model YC6112 YC6112 YC6112 YC6112 ZLQ ZLQ ZLQ ZLQ Parameters (G3000) (G3100) (G3200) (3300) Air intake type Cylinder diameter (mm) Piston stroke (mm) Total displacement (L) Rated power (kW) Rated speed (r/min) Maximum torque (Nm) Speed at maximum torque (r/min) Full load minimum fuel consumption (g/kWh) Maximum no-load speed (r/min) Fire ignition sequence Crankshaft rotation direction (Static) Fuel injection advance angle (BTDC) (°CA) Emission standard Noise limits [dB(A)]

YC6112 ZQ (G3500)

Turbocharged inter-cooled

YC6112 ZQ (G3600)

YC6112 ZQ (G3700)

Turbocharged 112 132 7.8

155

162

177

199

155

2300

140 2500

147 2300

814

820

895

980

700

650

1400~ 1600

1300~ 1500

1400~ 1600

1400

1400~1700

735 1300~ 1500

≤215

2600~2680

2680~2760

2750~2850

2600~ 2680

1-5-3-6-2-4 Anticlockwise (View from power output end)

9~13

6~9

9~13

11~13

Euro I ≤117

≤118

178

≤117

YUCHAI Engine Service Manual Table 6-7 YC6112ZLQ series engine technical specifications Engine model Parameters

YC6112ZLQ (G4400)

YC6112ZLQ (G4500)

Air intake type

112

Piston stroke (mm)

132

Total displacement (L)

7.8 147

Rated speed (r/min) Maximum torque (Nm)

170 2000

850

Speed at maximum torque (r/min) Full load minimum fuel consumption (g/kWh) Maximum no-load speed (r/min)

950 1300~1500

221

2300

2200

1030

1150

≤220

2300~2380

≤225

2500~2580 1-5-3-6-2-4

Anticlockwise (View from power output end)

(Static) Fuel injection advance angle (BTDC) (°CA)

6~8

Emission standard Noise limits [dB(A)]

209

1400~1600

≤210

Fire ignition sequence Crankshaft rotation

YC6112ZL Q (G5400)

Turbocharged inter-cooled

Cylinder diameter (mm)

Rated power (kW)

YC6112ZLQ (G8600)

6~9

Euro II ≤116

Euro I ≤117

179

8~10

≤119

YUCHAI Engine Service Manual Table 6-8 YC6L series engine technical specifications Engine model Parameters

YC6L350-20 (L3000)

Air intake type

YC6L330-20 (L3300)

YC6L310-20 (L3200)

Turbocharged inter-cooled

Cylinder diameter (mm)

113

Piston stroke (mm)

140

Total displacement (L)

8.424

Rated power (kW)

258

243

228

Rated speed (r/min)

2200

2200

2200

Maximum torque (Nm)

1400

1280

1150

Speed at maximum torque (r/min) Full load minimum fuel consumption (g/kWh) Exhaust smoke intensity (FSN)

≤1400

≤1400

≤1400

≤198

≤198

≤198

≤2.0

Emission standard

Euro II

(Static) Fuel injection advance angle (BTDC) (°CA)

8°~10°

180

YUCHAI Engine Service Manual Table 6-9 YC6M series engine technical specifications Engine model Parameters

YC6M220G (M3000)

Air intake type

YC6M240G (M3100)

Turbocharged inter-cooled

Turbocharged

Cylinder diameter (mm)

120

Piston stroke (mm)

145

Total displacement (L) Rated power (kW)

9.839 162

Rated speed (r/min) Maximum torque (Nm)

175 2200

880

Speed at maximum torque (r/min) Full load minimum fuel consumption (g/kWh) Coefficient of torque reserve

YC6M-360-20 (L3200)

1550

1300~1500

1200~1400

≤210

≤200 1.316

Beijing I

181

2100 1000

1.28

Emission standard (g/kWh)

266

1.28 Euro II

YUCHAI Engine Service Manual

62

Fitting Clearance of Main Parts and Components

Table 6-10 Fitting clearance of main parts and components of YC4108 series engine S/N

1 2 3

4

5

6

7 8 9 10 11 12 13 14 15 16

17

Fitting position

Drawing dimensions

Exhaust valve seat hole / Exhaust valve seat Intake valve seat hole / Intake valve seat Valve guide pipe bore / Outer diameter of valve guide pipe Valve guide pipe bore / Exhaust valve rod diameter Valve guide pipe bore / Intake valve rod diameter Valve rocker shaft seat hole / Valve rocker shaft Cylinder sleeve / Bottom of the piston skirt Valve tappet hole / Valve tappet Camshaft sleeve base hole / Camshaft sleeve Camshaft sleeve hole/ Camshaft journal Timing idle gear sleeve hole / Idler shaft Timing idle gear / Idler shaft Piston ring groove / First compression ring Piston ring groove / Second compression ring Piston ring groove / Oil ring Connecting rod bearing shell hole / Connecting rod journal Connecting 4108Q rod sleeve / 4108ZQ Piston pin

Fitting property

Interference

0.045~0.095

Interference

0.089~0.139

Interference

0.010~0.046

Radial clearance

0.040~0.081

Radial clearance

0.025~0.066

Radial clearance

0.020~0.062

Radial clearance

0.130~0.172

Radial clearance

0.020~0.093

Interference

0.057~0.106

Radial clearance Radial clearance

182

Unit: mm Fitting clearance (Interference )

0.03~0.09 0.03~0.09

Axial clearance

0.07~0.25

Axial clearance

0.085~0.135

Axial clearance

0.09~0.125

Axial clearance

0.030~0.065

Radial clearance

0.06~0.128

Radial clearance

0.025~0.042

YUCHAI Engine Service Manual

S/N

18 19 20 21 22 23 24

25

26 27

Fitting position

Drawing dimensions

Piston pin 4108Q seat hole / Piston pin 4108ZQ Main bearing hole / Main journal Camshaft space ring / Camshaft thrust plate Thickness of oil pump rotor / Pump body hole depth Outer rotor outer ring / Oil pump body hole Oil pump shaft sleeve (I) / Oil pump shaft Oil pump shaft sleeve (II) / Oil pump shaft Piston ring end gap clearance

Fitting property

Radial clearance

Fitting clearance (Interference ) 0.005~0.018 0.005~0.018

Radial clearance

0.060~0.144

Axial clearance

0.01~0.02

Axial clearance

0.05~0.101

Radial clearance Radial clearance Radial clearance

0.025~0.063

First compression ring

Clearance

0.4~0.6

Second compression ring

Clearance

0.3~0.45

Oil ring

Clearance

0.25~0.4

Axial clearance

0.1~0.27

Clearance

0.07~0.25

Crankshaft axial clearance Meshing clearance between gears

183

0.15~0.33

0.026~0.063

YUCHAI Engine Service Manual Table 6-11 Fitting clearance of main parts and components of YC4110 series engine S/N 1 2 3 4 5 6

7

8

9

10

11

12

13 14

Fitting position

Drawing dimensions

Exhaust valve seat hole / Exhaust valve seat Intake valve seat hole / Intake valve seat Valve guide pipe bore / Valve guide pipe Valve guide pipe bore / Exhaust valve Valve guide pipe bore / Intake valve

Fitting property

Unit: mm Fitting clearance (Interference)

Interference

0.075~0.12

Interference

0.09~0.14

Interference

0.013~0.048

Radial clearance Radial clearance

0.051~0.094 0.025~0.069

Valve sinkage

0.9±0.15

Valve 4110Q rocker shaft seat hole / 4110ZQ/Z Valve LQ rocker shaft Valve tappet hole / Valve tappet Cylinder 4110Q sleeve / Bottom of the 4110ZQ/ZL piston Q skirt Cam 4110Q bearing hole / 4110ZQ/ZL Camshaft Q sleeve Camshaft sleeve hole / Camshaft journal Timing 4110Q idle gear sleeve hole / 4110ZQ/ZL Idler Q shaft Timing idle gear / Idler shaft

0.04~0.012 Radial clearance

Radial clearance Radial clearance Radial clearance

0.02~0.09

0.015~0.053 0.130~0.185

0.133~0.175 0.114~0.191

Interference 0~0.126 Radial clearance

0.03~0.09 0.005~0.056

Radial clearance

Piston ring groove height / First compression ring height 184

0.043~0.081

Axial clearance

0.05~0.38

Axial clearance

0.085~0.135

YUCHAI Engine Service Manual

15 16

17

18

19

20

21

22 23 24

25

Piston ring groove height / Second compression ring height Piston ring groove height/ Oil ring height

Axial clearance

0.05~0.085

Axial 0.05~0.065 clearance First compression ring: 0.4~0.6 Second compression ring: 0.35~0.55 Third compression ring (oil ring): 0.3~0.55

Piston ring gap (pressed in Φ110.00 bore gauge)

Connecting Red rod big end bearing hole / Connecting rod journal Blue (with bearing shell) Connecti 4110Q ng rod sleeve 4110ZQ/ZL hole / Q Piston pin Piston 4110Q pin seat hole / 4110ZQ/ZL Piston Q pin Main bearing Red hole / Main journal (with Blue bearing shell) Crankshaft thrust face / Crankshaft thrust plate Camshaft thrust face / Camshaft thrust plate The meshing clearance between the gears Engine body Red cylinder hole/ Outside diameter of Blue cylinder sleeve

0.04~0.09 Radial clearance

0.05~0.10

0.025~0.042 Radial clearance

Radial clearance

Radial clearance Axial clearance Axial clearance Backlash

0.005~0.038

0.005~0.018

0.075~0.121 0.077~0.120 0.07~0.2 0.05~0.22 0.07~0.30 0.012~0.40

Clearance 0.018~0.46

185

YUCHAI Engine Service Manual Table 6-12 Fitting clearance of main parts and components of YC6112 and YC4112 series engine

S/N

1 2

3

4

5

6

Fitting position

Drawing dimensions

Exhaust valve seat hole / Exhaust valve seat Intake valve seat hole / Intake valve seat Cylinder cover Valve guide pipe bore / Outer diameter of valve guide Valve guide pipe bore / Exhaust valve rod diameter Valve guide pipe bore / Intake valve rod diameter Valve rocker sleeve inner hole / Rocker shaft

Fitting property

Unit: mm Fitting clearance (Interference)

Interference

0.040~0.086

Interference

0.042~0.088

Interference

0.013~0.048

Radial clearance

0.051~0.094

Radial clearance

0.025~0.069

Radial clearance

0.02~0.09

Radial clearance

0.126~0.164

Radial clearance

0.015~0.053

Interference

0.114~0.191

Group I 7

8 9 10

11

13

14

15

Cylinder sleeve / Maximum diameter of the bottom of piston skirt

Group II

Valve tappet hole / Valve tappet Camshaft sleeve base hole / Camshaft sleeve Camshaft sleeve hole/ Camshaft journal

Radial clearance

Timing idle 6112 gear sleeve hole / Idler 4112 shaft Piston ring groove height / First compression ring height Piston ring groove height / Second compression ring height Piston ring groove height/ Oil ring height

Radial clearance

186

0.076~0.137 0.043~0.081 0.005~0.056

Axial clearance

0.1~0.125

Axial clearance

0.105~0.155

Axial clearance

0.05~0.1

YUCHAI Engine Service Manual

16

Piston ring gap (pressed in bore gauge)

17

Connecting rod bearing shell hole / Connecting rod journal

Radial clearance

0.056~0.101

18

Connecting rod sleeve hole / Piston pin

Radial clearance

0.018~0.03

19

Piston pin seat hole / Piston pin

Radial clearance

0.013~0.024

20

21 22 23

Main Red bearing hole / Main Blue journal Crankshaft thrust face / Crankshaft thrust tile Spacer bush / Camshaft thrust plate Meshing clearance between the gears

Clearance

Radial clearance 37.06~37.11/36.91~36.96 4.674~4.724/4.5~4.57

Axial clearance Axial clearance Backlash

187

0.35~0.65

0.075~0.121 0.077~0.124 0.1~0.2 0.104~0.224 0.08~0.30

YUCHAI Engine Service Manual Table 6-13 Fitting clearance of main parts and components of YC6105ZQC, YC6108ZQ and YC6108ZQN series engine S/N 1 2 3 4 5 6 7 8 9 10 11

Fitting position

Drawing dimensions

Exhaust valve seat hole / Exhaust valve seat Intake valve seat hole / Intake valve seat Cylinder cover guide hole diameter/ Outer diameter of valve guide Valve guide pipe bore / Exhaust valve Valve guide pipe bore / Intake valve Valve sinkage Valve rocker hole / Valve rocker shaft Valve tappet hole / Valve tappet Camshaft sleeve hole/ Camshaft journal Timing idle gear sleeve hole / Idler shaft Thickness of timing idle gear / Idler shaft height

Fitting property

Unit: mm Fitting clearance (Interference)

Interference

0.045~0.095

Interference

0.089~0.139

Interference

0.010~0.046

Radial clearance

0.040~0.081

Radial clearance

0.025~0.066 0.8~1.2

Radial clearance

0.020~0.062

Radial clearance

0.020~0.093

Radial clearance

0.06~0.109

Radial clearance

0.025~0.075

Axial clearance

0.07~0.25

YC6108ZQ, YC6108ZQN (12~16)

14

Piston ring groove height / First compression ring height Piston ring groove height / Second compression ring height Piston ring groove height/ Oil ring height

15

Piston ring gap (pressed inΦ108.00 bore gauge)

16

Cylinder sleeve / Bottom of the piston skirt

12

13

First compression ring: Second compression ring: Oil ring:

Axial clearance

0.094~0.134

Axial clearance

0.005~0.085

Axial clearance

0.04~0.075

Opening clearance

0.45~0.6 0.3~0.45 0.25~0.4

Radial clearance

0.013~0.195

Axial clearance

0.08~0.12

Axial clearance

0.08~0.115

YC105ZQC (17~21) 17 18

Piston ring groove height / First compression ring height Piston ring groove height / Second 188

YUCHAI Engine Service Manual

19 20

21

22

23 24 25 26 27 28

compression ring height Piston ring groove height/ Oil ring height First compression ring: Piston ring gap (pressed Second compression ring: inΦ105.00 bore gauge) Oil ring: Cylinder sleeve / Bottom of the piston skirt Connecting rod big end bearing hole (with bearing shell) / Connecting rod journal Connecting rod sleeve hole / Piston pin Piston pin seat hole / Piston pin Main bearing hole / Main journal (with bearing shell) Crankshaft thrust face / Crankshaft thrust plate Spacer bush / Camshaft thrust plate Meshing clearance between the gears

189

Axial clearance

0.04~0.075

Opening clearance

0.4~0.60 0.5~0.7 0.3~0.6

Radial clearance

0.013~0.172

Radial clearance

0.04~0.1

Radial clearance

0.020~0.039

Radial clearance

0.005~0.018

Radial clearance

0.05~0.12

Axial clearance

0.1~0.27

Axial clearance

0.16~0.26

Backlash

0.07~0.30

YUCHAI Engine Service Manual Table 6-14 Fitting clearance of main parts and components of YC6108ZLQB series engine

S/N

1 2 3 4 5

Fitting position Exhaust valve seat hole/ Exhaust valve seat Intake valve seat hole/ Intake valve seat Cylinder cover valve guide pipe bore / Valve guide pipe Valve guide pipe bore/ Exhaust valve Valve guide pipe bore / Intake valve

6

Valve sinkage

7

Valve rocker shaft seat hole / Valve rocker shaft

8

Cylinder sleeve/ Bottom of the piston skirt

9 10 11 12 13

14

15

16 17

Drawing dimensions

Valve tappet hole/ Valve tappet Cam bearing hole/ Camshaft sleeve Camshaft sleeve hole/ Camshaft journal Timing idle gear sleeve hole / Idler shaft Timing idle gear/ Idler shaft Piston ring groove height/ First compression ring height Piston ring groove height/Second compression ring height Piston ring groove height/ Oil ring height Piston ring gap (pressed inΦ108.00 bore gauge)

Fitting property

Unit: mm Fitting clearance (Interference)

Interference

0.045~0.095

Interference

0.089~0.139

Interference

0.010~0.046

Radial clearance

0.040~0.081

Radial clearance

0.025~0.066 1.0~1.3

Radial clearance

0.020~0.062 0.0175~0.05

Radial clearance 0.015~0.0475

First compression ring: Second compression ring: Oil ring: 190

Radial clearance

0.020~0.093

Interference

0.057~0.106

Radial clearance

0.06~0.109

Radial clearance

0.03~0.09

Axial clearance

0.07~0.25

Axial clearance

0.085~0.135

Axial clearance

0.09~0.125

Axial clearance

0.03~0.065 0.4~0.6 0.35~0.55 0.03~0.55

YUCHAI Engine Service Manual

18

19 20 21 22 23 24 25

26 27 28

29

30

Connecting rod big end bearing hole / Connecting rod journal (with bearing shell) Connecting rod sleeve hole / Piston pin Piston pin seat hole / Piston pin Main bearing hole / Main journal Crankshaft thrust face / Crankshaft thrust plate Camshaft thrust face / Camshaft thrust plate Meshing clearance between the gears The clearance between intake valve and rocker (cold state) The clearance between exhaust valve and rocker (cold state) Compression clearance Fuel injection pump transmission shaft sleeve/ Bushing Sleeve hole/ Fuel injection pump transmission shaft Fuel injection pump transmission shaft/ Transmission thrust ring

191

Radial clearance

0.06~0.146

Radial clearance

0.025~0.042

Radial clearance

0.005~0.018

Radial clearance

0.05~0.15

Radial clearance

0.1~0.27

Axial clearance

0.1~0.20

Backlash

0.07~0.25

Clearance

0.40±0.05

Clearance

0.45±0.05

Clearance

0.9~1.1

Interference

0.057~0.106

Radial clearance

0.06~0.109

Axial clearance

0.3~0.5

YUCHAI Engine Service Manual Table 6-15 Fitting clearance of main parts and components of YC6L series engine S/N

1 2 3 4 5

6

7

8 9 10 11 12 13

14

15

16 17

Fitting position

Drawing dimensions

Exhaust valve seat hole/ Exhaust valve seat Intake valve seat hole/ Intake valve seat Cylinder cover valve guide pipe bore / Valve guide pipe Valve guide pipe bore/ Intake valve Valve guide pipe bore / Exhaust valve

Fitting property

Interference

0.035~0.085

Interference

0.045~0.095

Interference

0.017~0.039

Radial clearance

0.040~0.070

Radial clearance

0.040~0.070 Intake valve 0.55±0.15 Exhaust valve 0.6±0.15

Valve sinkage Valve rocker shaft sleeve hole/ Valve rocker shaft Cylinder sleeve/ Bottom of the piston skirt Valve tappet hole/ Valve tappet Cam bearing hole/ Camshaft sleeve Camshaft sleeve hole/ Camshaft journal Timing idle gear sleeve hole / Idler shaft Timing idle gear/ Idler shaft Piston ring groove height/ First compression ring height Piston ring groove height/Second compression ring height Piston ring groove height/ Oil ring height Piston ring gap (pressed inΦ113.00 bore gauge)

Unit: mm Fitting clearance (Interference)

First compression ring: Second compression ring: Oil ring: 192

Radial clearance

0.018~0.048

Radial clearance

0.114~0.149

Radial clearance

0.025~0.089

Interference

0.057~0.106

Radial clearance

0.06~0.109

Radial clearance

0.03~0.09

Axial clearance

0.07~0.25

Axial clearance

0.108~0.172

Axial clearance

0.06~0.110

Axial clearance

0.03~0.08 0.30~0.45 0.60~0.85 0.3~0.55

YUCHAI Engine Service Manual

18

19 20

21

22 23 24 25

26

27

28

29

Connecting rod big end bearing hole / Connecting rod journal (with bearing shell) (unit assembly)

Red(hole) + Red(shaft) + Red(shell)*2 Red(hole) + Blue(shaft) + Red(shell) + Blue(shell) Blue(hole) + Blue(shaft) + Blue(shell)*2 Blue(hole) + Red(shaft) + Red(shell) + Blue(shell)

Connecting rod sleeve hole / Piston pin Piston pin seat hole / Piston pin Main bearing hole / Main journal (with bearing shell) (unit assembly)

Red(hole) + Red(shaft) + Red(shell)*2 Red(hole) + Red(shaft) + Red(shell) + Blue(shell) Blue(hole) + Blue(shaft) + Blue(shell)*2

Crankshaft thrust face / Crankshaft thrust plate Camshaft thrust face / Camshaft thrust plate Meshing clearance between the gears The clearance between intake valve and rocker (cold state) The clearance between exhaust valve and rocker (cold state) Fuel injection pump transmission shaft sleeve/ Bushing Sleeve hole/ Fuel injection pump transmission shaft Fuel injection pump transmission shaft/ Transmission thrust ring

193

Radial clearance

0.040~0.092 0.045~0.097 0.052~0.105 0.047~0.100

Radial clearance

0.020~0.037

Radial clearance

0.009~0.022

Radial clearance

0.050~0.105 0.052~0.108 0.055~0.110 0.053~0.107

Axial clearance

0.1~0.2

Axial clearance

0.16~0.26

Backlash

0.07~0.25

Clearance

0.35±0.05

Clearance

0.40±0.05

Interference

0.057~1.106

Radial clearance

0.06~0.109

Axial clearance

0.3~0.5

YUCHAI Engine Service Manual Table 6-16 Fitting clearance of main parts and components of YC6M series engine S/N

1 2 3 4 5

Fitting position

Drawing dimensions

Exhaust valve seat hole/ Exhaust valve seat Intake valve seat hole/ Intake valve seat Cylinder cover valve guide pipe bore / Valve guide pipe Valve guide pipe bore/ Exhaust valve Valve guide pipe bore / Intake valve

Fitting property

Interference

0.036~0.085

Interference

0.036~0.085

Interference

0.005~0.034

Radial clearance

0.060~0.086

Radial clearance

0.060~0.118 1.3~1.6

Intake 6

Valve sinkage Exhaust

7 8 9 10 11 12 13

14

15

16

Unit: mm Fitting clearance (Interference)

Valve rocker shaft seat hole / Valve rocker shaft Valve tappet hole/ Valve tappet Cylinder sleeve/ Bottom of the piston skirt Cam bearing hole/ Camshaft sleeve Camshaft sleeve hole/ Camshaft journal Timing idle gear sleeve hole / Idler shaft Timing idle gear/ Idler shaft Piston ring groove height/Second compression ring height Piston ring groove height/ Oil ring height

1.1~1.4

0.01

Piston ring gap (pressed inΦ120.00 bore gauge)

Radial clearance

0.012~0.066

Radial clearance

0.025~0.089

Radial clearance

0.11~0.152

Interference

0.057~0.107

Radial clearance

0.04~0.12

Radial clearance

0.043~0.081

Axial clearance

0.099~0.167

Axial clearance

0.075~0.115

Axial clearance

0.05~0.09

First compression ring: 0.035~0.55 Second compression ring: 0.6~0.8 Third compression ring: 0.25~0.45

194

YUCHAI Engine Service Manual

17

18 19 20 21 22 23

Connecting rod big end bearing hole / Connecting rod journal (with bearing shell) Connecting rod sleeve hole / Piston pin Piston pin seat hole / Piston pin Main bearing hole / Main journal (with bearing shell) Crankshaft thrust face / Crankshaft thrust plate Camshaft thrust face / Camshaft thrust plate Meshing clearance between the gears

195

Radial clearance

0.083~0.118

Radial clearance

0.040~0.061

Radial clearance

0.002~0.015

Radial clearance

0.103~0.147

Axial clearance

0.102~0.305

Axial clearance

0.06~0.22

Backlash

0.07~0.25

YUCHAI Engine Service Manual

63

Tightening Torque of Main Bolts

Table 6-17 Tightening torque of YC4108 engine main bolts Name

Tightening torque (Nm)

Name

Tightening torque (Nm)

Main bearing bolt

220~300

Cylinder cover bolt

160~230 (Phosphating) 220~300 (Blueing)

160~200

Flywheel bolt

180~240

≥300

Camshaft gear lock bolt

80~100

Connecting rod bolt Crankshaft belt fastening bolt

Table 6-18 Tightening torque of YC4110 engine main bolts Name

Tightening torque (Nm)

Name

Tightening torque (Nm)

Main bearing bolt

180~260

Cylinder cover bolt

180~260

Connecting rod bolt

150~230

Flywheel bolt

170~220

Table 6-19 Tightening torque of YC4112 engine main bolts Name

Tightening torque (Nm)

Name

Tightening torque (Nm)

Main bearing bolt

180~260

Cylinder cover bolt

180~260

Connecting rod bolt

150~230

Flywheel bolt

160~240

Table 6-20 Tightening torque of YC6105ZQC engine main bolts Name

Tightening torque (Nm)

Name

Tightening torque (Nm)

Main bearing bolt

150~170

Cylinder cover bolt

160~230

Connecting rod bolt

190~260

Flywheel bolt

180~240

Table 6-21 Tightening torque of YC6108ZQ engine main bolts Name

Tightening torque (Nm)

Name

Tightening torque (Nm)

Main bearing bolt

230~300

Cylinder cover bolt

160~230

Connecting rod bolt

190~260

Flywheel bolt

180~240

196

YUCHAI Engine Service Manual Table 6-22 Tightening torque of YC6108ZLQB engine main bolts Name

Tightening torque (Nm)

Name

Tightening torque (Nm)

Main bearing bolt

230~300

Cylinder cover bolt

220~300

190~260

Flywheel bolt

180~220

120~140

Camshaft timing gear bolt

100~120

Connecting rod bolt Shock absorber bolt

Table 6-23 Tightening torque of YC6112 engine main bolts Name

Tightening torque (Nm)

Main bearing bolt

180~260

Connecting rod bolt

150~230

Cylinder cover bolt

180~260

Flywheel bolt

160~240

Name Shock absorber bolt Camshaft timing gear bolt Idle gear shaft bolt

Tightening torque (Nm) 271~298 54~61 200~240

Table 6-24 Tightening torque of YC6L engine main bolts Name

Tightening torque (Nm)

Name

Tightening torque (Nm)

Main bearing bolt

30→150→Further 90°

Cylinder cover bolt

30→150→Further 100°

Connecting rod bolt Silicone oil shock absorber bolt

30→60→Further 60°

Flywheel bolt

230

140

Camshaft timing gear bolt

100~120

Table 6-25 Tightening torque of YC6M engine main bolts Name

Tightening torque (Nm)

Name

Tightening torque (Nm)

Main bearing bolt

250~275

Cylinder cover bolt

Main: 300 Auxiliary: 150

160~200

Flywheel bolt

200~220

Connecting rod bolt Silicone oil shock absorber bolt

100~120

197