Foton Series Light Bus. Instruction — part 9

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6.6 Technical maintenance for air intake system

6.6.1 Air filter

Detach air filter and take out element. Check filter appearance or if it is too dirty, distored, damaged or oil

stained. Replace if necessary.

Clean the air filter element by compressed air if the element is contaminated by dust. Blow the dust away by

compressed air from element inside.

●Caution:

(1) Do not blow the element from outside which will blow dust into the element.

(2) Do not use any detergent or water to wash the paper element.

Clean air filter case and air intake pipe inside.

Secure all parts firmly during mounting of air filter and element. Loose connection would let dirty air enter

cylinder.

For air filter maintenance of BJ491EQ1 multi-point electronic fuel injection please see vehicle service

instruction or air filter service instruction.

6.6.2 Air intake pipe

Check the tightness of the joint between air intake pipe and air filter, and remove the leaking immediately.

Chapter 7 BJ491EQ1 Gasoline Engine Faults and Troubleshooting

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Chapter 7 BJ491EQ1 Gasoline Engine

Faults and Troubleshooting

7.1 Gasoline Engine Troubleshooting Summary

During gasoline engine operation, there will be some factors that gradually deteriorate its technical condition

such as part wear, distortion, incorrect use and technical service. When any of its technical data exceeds the

specification, engine has already had faults. Engine can not operate well until any fault on it has been eliminated.

With faults on it, engine’s power and economy will be reduced, and its emission will become worse too. Moreover,

Faults may cause parts early wear or even accident.

Some faults such as air in the fuel system, clogged filter, loose drive belt can be corrected after technical

maintenance and adjustment. However, others could not be elinminated just by the general maintenance and

adjustment methods. These faults includes damaged cylinder gasket, severe piston ring wear, valve cone face wear,

excessive bearing shell wear. Such faults can be removed only by dismantle- to-repair, or replacement parts and

components.

● Note:

(1) Remove the fault from the gasoline engine in time if any. To remove the faults, check and analyze

carefully, do not disassemble engine blindly.

(2) The operators should be familiar with the structure of the gasoline engine and its technical data, technical

requirements to dismantling and assembling. He must know how to perform service procedures and use service

tools.

(3) The complicated faults should be diagnosed and eliminated by the technical personnel using relevent

tools. If a user can’t determine the faults and has no required technical condition, he is suggested to approach to

FOTON authorized service station for help.

7.2 Diagnosis Basics -- Gasoline Engine Electronic Control Fuel Injection System

The gasoline engine electronic fuel injection system is sophisticated. Before faults diagnosis, the operator

should master the system’s principle, structure, service procedure and service tool application. First of all, he has

to determine if the faults acutally come from electronic fuel injection system. If there is a fault in gasoline engine

while malfunction indicator in instrument panel does not lit, the fault can not come from fuel injection system.

Fault diagnosis and check require special tool and tester. Operator should know them better before using

them, including knowing their function, structure and operating method. Common tools and tester includes circuit

test probe, multimeter and relevent testers.

To diagnose the faults in engine fuel injection system, you should be familiar with the following knowledge:

(1) The general information and basic principle of the electronic control fuel injection system.

(2) Performances of sensors, ECM and actuating devices, and their technical performance as well.

(3) The interface and terminal of the ECM and various sensors

7.3 Notes to Diagnosis-Gasoline Engine Electronic Control Fuel Injection System

7.3.1

DO NOT open the ECM cover, ECM is not serviceable. Once ECM cover has opened, it must be

damaged even if it seems to operate well for the moment.

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7.3.2

During engine operation and service, never splash water on engine harnesses and sensors, which may

cause short circuit.

7.3.3

Faults on wire and its connections mainly include the open circuit, short circuit and grounding. The open

circuit is generally due to wire break-off and bad contact. Wire normally breaks off on connection position, thus

connection should be checked carefully. The bad contact may give rise to the terminal oxidation and the entry of

foreign materials. Wiring connects directly to body (grounding) causes short circuit. To check this, inspect if wire

conductor touches vehicle body or frame due to its insulating wrap has been damaged.

7.3.4

To check open circuit, unclip the ECM and related sensor connectors, and then measure the resistance

between the connecting terminals so as to confirm whether there is the open circuit or contact is damanged.

7.3.5

To check grounding or short circuit, detach wire’s two ends and measure resistance between the connecting

terminal and body (ground).Resistance that is more than 1Ω is acceptable.

7.3.6

After having turned ignition swithe on, never disconnect any 12V electrical connections, these connections

include cables of battery, idle speed control valve, injector, electric fuel pump, ignition system, ECM circuit, and

A/C wiring etc.

7.3.7

The digital multimeter should be used to check the sensors and ECM. Use other tester may damage the

sensors and ECM.

7.3.8

If “check engine” light keeps on during engine operation, find out the possible cause and remove it

A.S.A.P..

7.3.9

Check immediately if engine fuel economy become deteriorated. Use inferior fuel will damage the

oxygen sensor and three-way catalytic converter.

7.3.10

Once there is misfire happening in certain cylinder, intermediately stop driving and eliminate the faults.

Otherwise unburned gas mixture may burn in the exhaust system, which will quickly damage the oxygen sensor

and three-way catalytic converter. If it is difficult to remove such fault in a short time, disconnect the spark plug

from the misfire cylinder.

7.4 Gasoline EngineTroubleshooting Procedures

7.4.1 Unable or hard to startup

S/N Parts/components

Possible Cause

Solutions

1

Sensors

⑴ Poor connections -- coolant

temperature sensor, intake temperature

sensor

⑵ Incorrect crankshaft position sensor

clearance

⑶ Foreign objects and oil stains on

crankshaft pulley

⑷ ECM has not plugged in well

⑴ Reconnect the related harness
⑵ Check and adjust it to the proper

clearance

⑶ Remove foreign objects and oil stains
⑷ Check ECM connector.

2

Starting System

⑴ Battery voltage is too low
⑵ Battery poor connection
⑶ Fuse breaks off
⑷ Starter is failure
⑸ Ignition switch is failure

⑴ Recharge the battery as required
⑵ Clean the terminal posts and tighten the

battery cable
⑶ Replace the fuse
⑷ Repair or replace the starter
⑸ Repair or replace the ignition switch

Chapter 7 BJ491EQ1 Gasoline Engine Faults and Troubleshooting

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S/N Parts/components

Possible Cause

Solutions

3

Fuel Supply

System

⑴ Fuel pump relay is failure
⑵ Fuel system pressure is insufficient
⑶ Injector is leaking

⑴ Replace the fuel pump relay or check the

connecting lead
⑵ Check the fuel level in tank and the

electric fuel pump working condition
⑶ Replace the injector

4

Ignition System

⑴ The ignition coil is failure
⑵ The high voltage cable is damaged
⑶ The spark plug is failure
⑷ The ignition system is poorly

connected.

⑴ Replace the ignition coil
⑵ Replace the high voltage cable
⑶ Adjust spark plug clearance, clear the

carbon deposit or replace the spark plug
⑷ Correctly connect the ignition system

5

Others

⑴ Valve has air leakage or is burnt out
⑵ Cylinder gasket is damaged
⑶ The intake manifold or vacuum pipe

is leaking
⑷ The piston, piston ring and cylinder

bore are damaged

⑴ Grind or replace the valve
⑵ Replace the cylinder gasket
⑶ Check the intake system, and remove the

air leakage
⑷ Repair or replace the piston, piston ring

or cylinder block

7.4.2 Engine Stalls

(Engine Rpm goes up and down constantly while throttle is opened)

S/N

Parts/components

Possible Cause

Solutions

1

Fuel System

⑴ Fuel is either enriched or too lean
⑵ The fuel system pressure is not
stable
⑶ The fuel filter is clogged
⑷ Fuel injector is clogged or fuel
leakage

⑴ Check whether the oxygen sensor and
fuel pressure regulator work normally
⑵ Check whether the electric fuel pump
works normally
⑶ Replace the fuel filter
⑷ Clean or replace the injector

2

Ignition System

⑴ The ignition coil secondary voltage
is too low
⑵ The spark plug electrode gap is
incorrect
⑶ The spark plug is burnt-out or has
serious carbon deposit

⑴ Check the ignition coil, replace if,
necessary
⑵ Adjust the spark plug electrode gap to
1.1mm±0.1mm
⑶ Clear away the carbon deposit or
replace the spark plug

3

Others

⑴ ECM ground lead is poorly
connected
⑵ The starting system voltage is not
within the range of 9 V to 16 V
⑶ The vacuum pipe is clogged or
leaking
⑷ The intake manifold is leaking
⑸ Poor valve sealing
⑹ Hydraulic tappet is failure
⑺ Excessive clearance between the
valve stem and valve guide

⑴ Confirm the ECM is connected reliably
⑵ Check whether the alternator output
voltage is proper
⑶ Check and clear the vacuum pipe
⑷ Check and remove the intake manifold
leakage
⑸ Grind the valve
⑹ Replace the hydraulic tappet
⑺ Replace the valve or valve guide

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7.4.3 Engine Knock

S/N

Parts/components

Possible Cause

Solutions

1

Cooling System

⑴Coolant temperature is too

high
⑵ Water pump belt is loosening
⑶ The radiator pipes are clogged
⑷ Thermostat is failure

⑴ Add coolant and remove the leakage
⑵ Tighten the belt
⑶ Check and clear radiator pipes
⑷ Replace the thermostat

2

Coolant Temperature

Sensor

Coolant

temperature

sensor

output drifts

Replace the coolant temperature sensor

3

Gasoline

The gasoline octane number is

too low

Change to use specified gasoline

4

The ignition timing is incorrect

Check the sensor operation and connection

5

Others

⑴ Compression ratio is too high
⑵

Excessive

combustion

chamber carbon deposit

⑴ Check the sizes of related parts
⑵ Clear carbon deposit inside combution

chamber

7.4.4 Insufficent Engine Power

S/N

Parts/components

Possible Cause

Solutions

1

Intake System

The air filter is clogged

Replace the air filter element

2

Fuel Supply System

⑴ Fuel is contaminated
⑵ Fuel pressure is too low

⑴ Replace it with specified 93# or up lead

free gasoline
⑵ Check the electric fuel pump and vacuum

pipes or replace the fuel pressure regulator

3

Ignition System

⑴ The ignition coil secondary

voltage is too low
⑵ The ignition is abnormal

⑴ Check the ignition coil, or replace the

ignition coil if necessary
⑵ Check the wire and sensor concerned

4

Others

⑴ The exhaust system is clogged
⑵ The exhaust valve opens

abnormally

⑴ Check and remove the exhaust system

clogging
⑵ Check the exhaust valve opening condition,

or replace the valve, camshaft and other parts

and components concerned if necessary

5

Others

⑴ Poor ECM grounding
⑵ The power system voltage not

within the range of 9 V to 16 V

⑴ Check the cable and confirm that the ECM

can ground reliably.
⑵ Check whether alternator output voltage is

normal, or replace alternator and regulator if

necessary

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7.4.5 Unsteady Engine Idle Speed

S/N

Parts/components

Possible Cause

Solutions

1

Sensor

⑴ Loose connectors -- intake

absolute pressure sensor, air

intake temperature sensor
⑵ The coolant temperature

sensor is failure

⑴ Check and connect all sensor connectors

again
⑵ Replace the coolant temperature sensor

2

Fuel System

⑴ Fuel injector has not plugged

in properly
⑵ The fuel system pressure is

not within 300kpa range
⑶ The injector is leaking or fuel

supply is insufficient

⑴ Check and connect the injector
⑵ Check the fuel system pressure, replace the

related parts if necessary
⑶ Check the injector, replace the injector if

necessary,

3

Ignition System

⑴ The ignition coil secondary

voltage is low
⑵ The high voltage cable is

leaking
⑶ The idle speed ignition

advance angle is not approx. 10º
⑷ The spark plug electrode

clearance is incorrect
⑸ The spark plug has carbon

deposit
⑹ The high voltage cable is

short circuit or has high internal

resistance

⑴ Replace the ignition coil if necessary
⑵ Replace the high voltage wire
⑶ Check the throttle position sensor, air

intake pressure sensor, and if necessary,

replace ECM
⑷ Check and adjust the spark plug clearance
⑸ Clear the carbon deposit, and if necessary,

replace the spark plug
⑹ Replace high voltage cable

4

Air Intake System

⑴ Air intake system is leak
⑵ The idle speed control valve is

failure
⑶ The throttle position sensor is

failure
⑷ The throttle opening is

incorrect

⑴ Check air intake system land eliminate

leakage
⑵ Replace the throttle valve body
⑶ Replace throttle position sensor
⑷ Check the accelerator cable and throttle

opening

5

Others

⑴ The cylinder pressure is

insufficient
⑵ The valve spring breakage or

excessive cam wear

⑴ Check and replace the related parts
⑵ Replace the related parts

6

Others

⑴ The power supply system

voltage is not within the range

9 V to 16 V, and idle speed

control valve fails to actuate
⑵ The ECM grounding is

incorrect

⑴ Check and repair the alternator and battery,

and if necessary, replace them
⑵ Correctly connect the ECM grounding wire

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7.4.6 Highter Emission at Idle

S/N

Parts/components

Possible Cause

Solutions

1

Cooling System

The

coolant

temperature

is

abnormal

Check the cooling system and remove the

faults

2

Ignition System

⑴ The idle speed ignition

advance angle is not approx. 10º
⑵ The spark plug is failure
⑶ The high voltage wire is

failure
⑷ The ignition coil works

abnormally

⑴ Check if all sensors work normally
⑵ Check, clear and adjust spark plug

clearance
⑶ Check or replace the high voltage wire
⑷ Check, and if necessary, replace the

ignition coil

3

Air intake System

⑴ The vacuum leakage
⑵ The crankcase ventilation

valve is failure

⑴ Check and remove the vacuum leakage
⑵ Clean or replace the crankcase ventilation

valve

4

oxygen

sensor,

three-way

catalytic

converter are failure

⑴ Use the leaded gasoline or the

gasoline

with

phosphate,

sulphure and impurities beyond

the specified values
⑵ certain cylinder has misfire
⑶The

oxygen

sensor

and

three-way catalytic converter are

damaged

⑴ Use the clean lead free gasoline as required
⑵ Check the fuel passage, circuit to remove

the misfire faults
⑶ Replace the oxygen sensor and three-way

catalytic converter

5

Fuel System

⑴ Fuel is insufficient in fuel

tank
⑵ The electric fuel pump works

unsteadily

⑴ Refill the fuel
⑵ Check the electric fuel pump and its circuit,

and if necessary, replace the electric fuel pump

6

Others

Valve is leaking or grabbed.

Check the matching condition of the valve

stem and valve guide to ensure that the valve

is clogged. Or grind to repair the valve.

7.4.7 Excessive Fuel Consumption

S/N

Parts/components

Possible Cause

Solutions

1

Fuel Pipe

The fuel pipe or joint is leaking

Tighten all gasoline pipe joint

2

Air Intake/Exhaust

System

⑴ The air filter is clogged
⑵ The exhaust system leakage

⑴ Check, clean or replace the air filter element
⑵ Remove the exhaust system leakage

3

Ignition System

⑴ Poor sensor wire connection
⑵ The water temperature sensor,

oxygen

sensor,

air

intake

temperature sensor are failure

⑴ Reconnect all sensor plugs
⑵ Check, and if necessary, replace the sensors

4

Poor Compression

⑴ The spark plug is failure
⑵ The high voltage wire is

failure

⑴ Check or replace spark plug
⑵ Replace the high voltage wire

Chapter 7 BJ491EQ1 Gasoline Engine Faults and Troubleshooting

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S/N

Parts/components

Possible Cause

Solutions

5

Poor Compression

⑴ Valve leakage
⑵ Failure hydraulic tappet
⑶ Weak valve spring
⑷ Cylinder gasket leakage
⑸ The piston ring is stuck or

broken
⑹ Excessive piston or cylinder

wear

⑴ Grind the valve
⑵ Check , rinse or replace the hydraulic

tappet
⑶ Replace the valve spring
⑷ Replace the cylinder gasket
⑸ Replace the piston ring
⑹ Repair or replace the related parts

6

Clutch

Poor clutch engagement, or

clutch slip

Check and adjust the clutch

7.4.8 Excessive Oil Consumption

S/N

Symptoms

Possible Cause

Solutions

1

Oil Leakage

⑴ The oil pan drain plug is loosen
⑵ The oil pan bolt is loosen
⑶ The oil pan gasket is damaged
⑷ The sprocket chamber cover

bolt is loosen
⑸ The cylinder head O-ring is

damaged
⑹ The crankshaft front/rear oil

seals are damaged
⑺ The pump bolts are loosen or

gasket damaged
⑻ Oil filter seat bolt is loosen or

gasket damaged

⑴ Tighten the oil pan drain plug
⑵ Tighten the oil pan fixing bolt
⑶ Replace the oil pan gasket
⑷ Tighten the bolt or replace the gasket
⑸ Replace the cylinder head O-ring
⑹ Replace the crankshaft front/rear oil seal
⑺ Tighten the inner fixing bolts or replace the

gasket
⑻ Tighten the oil filter fixing bolts or replace

the gasket

2

Poor Piston and

Cylinder Sealing

⑴ Oil ring has excessive wear or

gets damaged
⑵ Excessive wears on piston and

cylinder bore

⑴ Replace oil ring
⑵ Check or replace the piston and cylinder

block

3

Poor Valve

Sealing

⑴ The valve oil seal is damaged
⑵ Excessive valve stem and guide

wear

⑴ Replace the valve oil seal
⑵ Replace the valve and guide

4

Crankcase

Ventilation

System

The crankcase ventilation valve is

clogged

Check and clear up crankcase ventilation valve

5

Oil Consumption

is increasing

Gasoline engine operates at the

high speed under the small load

for a long time

Avoid that the gasoline operates at the high

speed under the small load condition for a long

time

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7.4.9 Abnormal Sounds From Gasoline Engine

S/N

Possible Cause

Solutions

1

The hydraulic tappet is failure which

afftects the valve clearance

Check or replace the hydraulic tappet

2

Too loose piston pin which generates the tap

sound

Replace the piston pin or the piston

3

Excessive wears on piston, piston ring and

cylinder bore

Check and replace the piston and piston ring; bore cylinder

4

Excessive wear on connecting rod bearing

shell

Replace the connecting rod bearing shell

5

Excessive main bearing shell wear

Replace the main bearing shell

6

Excessive crankshaft thrust washer wear

Replace the crankshaft thrust washer

7

Too big cam axial clearance

Replace the camshaft thrust washer

8

Excessive

timing

chain

and

timing

sprocket wear

Replace the timing chain and timing sprocket

9

The chain tensioner is failure

Replace the chain tensioner

10

Excessive combustion chamber carbon

deposite

Clear the combustion chamber carbon deposite

11

The gasoline specification does not conform

to the requirements

Use the specified gasoline

7.4.10 Engine Overheat

S/N

Possible Cause

Remedies

1

Insufficient Coolant

Add the coolant as required

2

Fan belt is loose or damaged

Adjust the tension of fan belt or replace the belt

3

Water pump is failure

Check and repair the water pump or replace the water

pump

4

Thermostat is failure

Replace the thermostat

5

Radiator, cylinder block, cylinder head and

pipes & passages are clogged or leaking

Clean, repair or replace the related parts

6

Silicone oil fan clutch is failure

Check and replace the silicone oil fan clutch

7

Ignition timing is too late

Check the ignition timing

8

Engine oil level or viscosity is low

Refill or change oil as required

9

Excessive

cylinder

head

combustion

chamber carbon deposite

Remove the combustion chamber carbon deposite

10

Exhaust system is clogged

Clear or replace the exhaust system parts and components

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7.4.11 Engine Oil Pressure Too Low

S/N

Possible Cause

Remedies

1

Oil leakage

Check or replace the related parts

2

Oil level or viscosity is low

Refill oil or replace oil as required

3

Oil temperature is too high

Cool the gasoline engine, check and repair the cooling

System

4

Oil pump pressure-limiting valve is failure

Check and repair the oil pump pressure-limiting valve

5

Oil pump is failure

Check and repair the oil pump or replace the oil pump

6

Oil strainer is clogged, connecting pipe

leakage

Clear oil strainer, and tighten the pipe joint

7

Oil filter is clogged

Replace the oil filter

8

Oil pressure gauge is failure

Replace the oil pressure sensing plug

9

Oil pressure gauge failure

Replace the oil pressure gauge

10

Excessive wears on main bearing shell,

connecting rod bearing shell or camshaft

bearing

Replace the bearing shell or bearing concerned

11

Serious oil leakage on rocker arm shaft or

chain tensioner

Check and tighten the related parts

7.4.12 Gasoline Engine Backfire

S/N

Parts/components

Possible Cause

Solutions

1

Ignition System

⑴ The spark plug electrode gap

is incorrect
⑵ The spark plug has carbon

deposit
⑶ The high voltage cable is

short circuit
⑷ The ignition coil secondary

voltage is insufficient

⑴ Adjust the spark plug electrode gap to

1.1mm±0.1mm
⑵ Clean the spark plug or replace the spark

plug
⑶ Replace the high voltage cable
⑷ Replace the ignition coil

2

Crankshaft Position

Sensor

Clearance between crankshaft

position sensor and crankshaft

pulley is incorrect

Check and adjust the clearance to the correct

value

3

Others

⑴ Valve leakage
⑵ Valve timing is incorrect
⑶ Air intake/exhaust pipe

leakage

⑴ Check the hydraulic tappet and valve
⑵ Check the valve and camshaft
⑶ Remove the air intake/exhaust pipe leakage

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7.4.13

Engine Acceleration Delay or Lagging (Depressing accelerator pedal will not change speed when

driving at various speed, on in worst case, the gasoline engine even stalls)

S/N

Parts/component

Possible Cause

Solutions

1

Fuel System

⑴ The fuel system pressure is

low
⑵ The injector drive circuit is

failure
⑶ The electric fuel pump is

damaged
⑷ The fuel system is clogged

⑴ Check the fuel pump fuel-supply pressure,

check whether the fuel filter is clogged, and

check the fuel pressure regulator
⑵ Check the injector drive circuit
⑶ Replace the electric fuel pump
⑷ Replace the fuel filter, and clear the pipes

2

Ignition System

Certain spark plug or high

voltage wire is failure

Replace the spark plug or high voltage wire

3

Voltage is abnormal The power supply system voltage

is not within the range of 9V to

16V

Check the alternator and battery

4

Others

The throttle is grabbed

Clear the carbon deposit, and if necessary,

replace the throttle valve body

7.4.14 Engine Fuel Cut-off or Misfire

(the gasoline engine trembles during the acceleration, and the

sound of fuel after burning can be heard from the exhaust pipe when the engine operates at idle speed and low

speeds)

S/N

Parts/components

Possible Cause

Solutions

1

Ignition System

⑴ The spark plug clearance is

incorrect
⑵ The spark plug has carbon

deposit
⑶ High resistance

⑴ Adjust the spark plug clearance
⑵ Clear the carbon deposit or replace the

spark plug
⑶ Replace high resistance cable

2

Fuel System

⑴ The fuel pressure is incorrect
⑵ The fuel filter is clogged
⑶ The injector is failure

⑴ Check whether the electric fuel pump

operates normally, and check the fuel pressure

regulator
⑵ Replace the fuel filter
⑶ Replace the injector

3

Others

⑴ The valve timing is incorrect
⑵ Valve leakage
⑶ The valve spring is broken or

failure
⑷ The camshaft is failure

⑴ Check the valve timing
⑵ Grind the valve, and check the hydraulic

tappet
⑶ Replace the valve spring
⑷ Replace the camshaft

4

Electromagnetic

disturbance

Serious

electromagnetic

disturbance

Check the high voltage wire for leakage

Chapter 8 Structure, Adjustment and Service of BJ483ZQB Diesel Engine

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Chapter 8 Structure, Adjustment and Service of

BJ483ZQB Diesel Engine

8.1 Precautions on Service and Adjustment of Diesel Engine

8.1.1

Non-professional personnel never tries to dismantle to repair a diesel engine. The customers should contact

the dealers or service stations authorized by FOTON Motor Company.

8.1.2

The operators should be familiar with the structure of diesel engine and its technical data, component

assembly relationship and the technical requirements for disassembly/assembly, and understand the proper

methods for assembly/assembly and the maintenance tools using. Customer who does not have necessary

technical skills and conditions is suggested to contact the service stations authorized by Fonton Motor Company.

8.1.3

The disassembly procedure is generally conducted in the following order: from the outside to the inside,

and from the assy. to the components. To improve the assembly efficiency and ensure the correctness of the

assembly, note to check and make marks on parts when disassembly. Clean the components disassembled and

inspect them carefully. The components which can be reused should be sorted and stored by the assy.. The

precision components should be divided from the common ones, and stored in a clean container.

8.1.4

The assembly procedure is generally conducted in the following order: from the inside to the outside, and

from the parts to the components and then from the components to assy.. When assembly, pay more attention to

the installation dimension, orientation, fit clearance, tightening torque and etc. to avoid the neglected installation,

incorrect installation, the scuffing of component fitting surface, and the entry of foreign material into the inside of

the machine. Use proper wrench and fastening torque on bolts and nuts. Use fittings correctly according to

regulations, including cotter pins, spring washer, retraining washer etc. Beside, during assembly, note to cross

check parts codes with assembling marks to ensure right locations and motional relations among parts.

8.1.5

Ensure that the diesel engine is in the clean, good working conditions at all times. Before the disassembly

or assembly, clean or wipe parts to guarantee them clean and ensure the quality of assembly. The complicated

adjustment and maintenance should be conducted in doors to prevent the inside of diesel engine from being

contaminated by the environment.

8.1.6

Watch out personal injury due to moving parts or wrongly use of tools during dismantling or service.

8.2 Service and Adjustment of Diesel Engine

8.2.1 Tightening of Cylinder Head

The cylinder head is tightened to the cylinder block through the cylinder head gasket using 10 main bolts and

8 auxiliary bolts. To prevent the air leakage, the cylinder head bolts should have the sufficient tightening torque at

installation. The cylinder head bolts should be evenly tightened three times in the specified sequence using the

special torque wrench. The tightening sequence and the torque of the cylinder head main bolts are: 40 – 50 N·m

for the first time; 90 – 100 N·m for the second time; and 145 – 160 N·m for the third time. The tightening

sequence and the torque of the cylinder head auxiliary bolts are: 10 – 15 N·m for the first time; 25 – 35 N·m for

the second time; and 45 – 55 N·m for the third time. The tightening operation starts from the center and alternately

extends to its surroundings in sequence every time (see Figure 8-1), and at the last time, it should be tightened to

the specified torque.

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Figure 8-1 The Tightening Sequence of Cylinder Head Bolt

● Note:

(1) The turbocharged diesel engine adopts the integrated cylinder head gasket. During installation, there is

no foreign material in the outer part of the retainer; otherwise it may cause the blow-out of the combustion gas.

(2) When the air leakage from the diesel engine’s cylinder head gasket occurs, use a torque wrench to

check the tightening torque of the cylinder head bolts which should be tightened after the diesel engine has cooled

down.

(3) The cylinder head bolt is a kind of special high-strength bolt, and it is prohibited to substitute it with the

regular bolt.

8.2.2 Assembly of Cylinder Liner

The cylinder liner is with the dry-type structure. Its body is fixed together with the intermediate fixing main

bearing cap by the pin, flushing with the planes of front/rear main bearing caps. It interlinks with the main bearing

cap by main bearing cap bolts.

If the wear of inner surface of the cylinder liner is above 0.35 mm, replace it.

Clean the outer surface of the cylinder liner as well as cylinder bore wall before assembling a cylinder liner.

Do not apply lubricating grease on them to avoid that the grease affects the contact between the cylinder and its

liner as well as their heat dissapation. Apply uniform pressure to press cylinder liner into cylinder block.

8.2.3 Tightening of Main Bearing Cap Bolt

The tightening torque of main bearing cap bolt is 160 – 170 N·m. Tighen evenly in three times in sequence:

the first: 40 – 50 N·m; the second: 90 – 100 N·m; and the third: 160 – 170 N·m.

8.2.4 Assembly of Piston

The Figures 8-2 and 8-3 show the piston with the elliptical and cone-shaped head on which there are 2 gas

grooves and 1 oil groove. On the top face of piston, there is a forward arrowhead installation mark which points to

the front of diesel engine. In addition, the outside diameter grouping mark is engraved on the piston. Select the

piston group whose dimension group matches that of cylinder liner to install.

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Figure 8-2 Piston and Connecting Rod

1-Piston; 2-Piston Ring; 3- Snap Ring; 4-Piston Pin; 5-Connecting Rod; 6-Connecting Rod Bushing; 7-Connecting Rod Cap;

8-Cumbustion Chamber

Figure 8-3 Piston and Piston Ring Structure

1-Barrel-Face Trapezoid Gas Ring; 2-Inner Chamfer Twist Type Gas Ring; 3-Spiral Spring Oil Ring

The piston pin seat locates in the middle section of the piston, and is used to support the piston pin. The

grooves at both ends of pin hole are used to install the snap ring which limits the piston pin axial movement.

There is an oil hole under the pin hole, which is used to collect the oil and lubricate the pin / seat friction surface.

Measure the wear of piston when repairing. Replace the piston if the wear of piston exceeds the standard

value.

● Note: The piston ring and piston should be replaced in pair.

8.2.5 Check and Assembly of Piston Ring

The piston ring is divided into gas ring and oil ring. Each piston 2 gas rings and 1 oil ring. The first gas ring

is a barrel-face trapezoid ring, the second gas ring is an inner chamfer twist type ring (the inner chamfer faces

upward when installation), and the third ring is a spiral spring oil ring (Figure 8-3).

The special tools are used to reassemble the piston ring (Figure 8-4). Install the spiral oil ring first, followed

by second and first rings.

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Figure 8-4 Installation of Piston Ring Using A Piston Ring Expander

Piston rings were set into cylinder liner under normal temperature. There should be proper gap at their opens

—so called “open gap”. Proper gap can help to avoid it being seized due to heat expansion, and reduce leakage

through gap to preserve energy and keep crankcase clean. The standard clearance values are as follows: first ring

0.25 – 0.40mm; second ring 0.25 – 0.40mm; oil ring 0.15-0.30mm.

Use a feeler to measure open gap after a piston has been put into a standard cylinder liner.

Wear on outer circle of a piston ring would enlarge open gap, air leakage would increase too. Replace ring

sets when gap exceeds limit.

The height clearance between ring and ring groove is called side clearance. Proper upper limit of side

clearance ensures ring could move in groove freely without sticking; and proper lower limit could help ring to

reduce oil pumping amount and restrain ring from moving up and down. Side clearance affects oil consumption.

Side clearance of each piston ring is as follows: 0.06 – 0.10 mm for the first ring; 0.04 – 0.08 mm for second

ring; and 0.02 – 0.06 mm for oil ring.

Use a feeler to measure side clearance after a piston ring has been put into its relating groove.

When to mount an oil ring, the lining spring connector should be installed opposite to the opening of oil ring

body.

After the piston ring has installed into the piston, the ring should move freely in the ring groove without

restriction. The opening positions of three piston rings should mutually stagger to each other.

Figure 8-5 Piston Ring Installation Position

8.2.6 Assembly of Piston Pin

The piston pin is fastened by a spring retaining ring. One end of the ring bends inwards. Use a long flat nose

pliers to snatch the bent on ring to take it out. No special tool is neede. (See Figure 8-6)

First Ring

Spiral Spring Opening

Spiral Spring Oil Ring

Second Ring

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Figure 8-6 Remove spring retaining ring with nose pliers

Heat piston to 100

℃

– 120℃ before mounting piston pin into piston.

● Note: When to install piston pin retaining ring, check locating ring surface for any damage.

8.2.7 Assembly of Connecting Rod and Its Bolts

The connecting rod connects the piston with the crankshaft. The body of connecting rod and its big end cap

are attached in pair using the locating bolt, they are not interchangeable (see Figure 8-7).

Figure 8-7 Connecting Rod Assembly

1-Connecting rod small end bushing; 2-Connecting rod body; 3-Connecting rod bolt; 4-Connecting rod upper bearing shell

5-Connecting rod lower bearing shell; 6-Connecting rod cap; 7-Connecting rod nut

Apply lubricating oil on thread surface before mounting connecting rod bolts, and tighten two bolts in three

times. The tightening torque of the connecting rod bolt is 55 – 65 N·m.

Since the central plane of the connecting rod body misaligns with that of the connecting rod big end in axial