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direction, i.e., the big end is eccentric to connecting rod body. Connecting rod can fit the crankshaft properly only
under following conditions: arrowhead mark on the top surface of piston points front; the marks (protuberated) on
connecting rods for cylinders No.1 and 3 face forward; and that for cylinders No. 2 and 4 face rearward. So, when
to reassemble the piston connecting rods, these for cylinders No. 1, 3 and for No. 2, 4 should be sorted and
reassembled respectively. The weight difference among groups should not be more than 5 g.
Figure 8-8 Upper/Lower Main Bearing Shell of Crankshaft
1-Upper main bearing shell; 2-Oil hole; 3-Locating protruded lip; 4-Lower main bearing shell
Before the piston connecting rod is installed into the cylinder liner, apply the clean oil on the outer surface of
piston, connecting rod small end and bearing shell surface. The openings of the first and second piston rings
should mutually stagger 180°, and avoid pointing to the direction of piston pin. The oil ring and the second ring
should stagger 90° (see Figure 8-5).
When the piston connecting rod is installed into the block, the piston head guide groove should face the
tappet side (injection pump side). After tightening the connecting rod bolt to the specified torque (55 – 65 N·m)
during assembly, check if the crankshaft rotates smoothly and if there is an axial clearance in the connecting rod
big end.
● Note: Replace the body and cap of the connecting rod in pair at the same time.
8.2.8 Assembly of Upper/Lower Bearing Shell of Crankshaft
The crankshaft journal of turbocharged diesel engine is supported on the block by the main bearing cap. The
upper bearing shell of crankshaft has the oil groove and hole (see Figure 8-8), and the upper and lower bearing
shells are not interchangeable.
When to press to mount the timing gear, the mark “X” on gear should face outward (see Figure 8-9).
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Figure 8-9 Gear Drive Mechanism
1-Injection pump gear, with Mark Y; 2-Idle gear, with marks Y, Y;
3-Camshaft gear, with marks X, X; 4-Crankshaft gear, with mark X
8.2.9 Assembly of Flywheel
The flywheel is installed by 6 bolts to ensure the reliable installation strength. During installation, tighten the
bolts clockwise three times with the tightening torque of 80 – 90 N·m.
Apply oil on bolts thread before mounting flywheel bolts.
8.2.10 Assembly of Timing Drive Mechanism
The turbocharged diesel engine’s gear drive mechanism includes: the injection pump drive gear, camshaft
gear, idle gear, crankshaft gear and other gears, as shown in Figure 8-9.
The open/close timing of the diesel engine’s intake/exhaust valves and fuel supply timing of injection pump
are strickly set in relation to the movement position of crankshaft. The camshaft gear, injection pump gear and
crankshaft gear are correlated via the timing idle gear. The crankshaft gear, camshaft gear, injection pump gear
and idle gear all have their own assembly marks.
A tilted convex rib is forged on the gear chamber cover, and there are the inscribed lines on the crankshaft
pulley (see Figure 8-10), which are used for the adjustment of top dead center.
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Figure 8-10 Crankshaft Pulley
Marks are inscribed on the surface of outer circle of the crankshaft pulley; 0-means the top dead center of piston;
6-means 6º before top dead center (crankshaft angle); 16-means 16º before top dead center (crankshaft angle)
When to mount timing gear drive mechanism, align these marks with each other to ensure the correct port
timing and fuel supply timing. Otherwise there would be some malfunctions happening such as engine fails to
start up, or its power goes down, oil consumption increases, or in worst case, the piston head could bump to valve
to cause damage.
After the installation of timing gear group, check the port timing.
If the complete gear drive mechanism is required to be replaced due to the unclear and invisible marks or
worn-out gear, please get to the professional service shop or the service stations authorized by Foton Motor
Company.
8.2.11 Assembly of Camshaft
The highlights on the assembly of the camshaft assy.:
(1) When pressing in the cam gear and idle gear, the gear marks “X, X” and “Y, Y” should face outwards
(see Figure 8-9).
(2) When to mount tappet into the tappet bore in cylinder block, apply the lubricating oil on them. Installed
tappet should be able to rotate by hand.
(3) After oil pump has been tightened, the camshaft should be able to rotate by hands.
8.2.12 Assembly of Intake / Exhaust Valve
The valve is used to control the open/close of the intake / exhaust passages.
Replace any worn out valve.
● Caution: The valve spring locking plate should be correctly installed into the spring seat, otherwise
locking plate might fall off to cause the valve dropping into the cylinder.
8.2.13 Valve Clearance
The valve clearance means the gap between the back end of valve stem and the rocker arm measured when
valve closes near the top dead center of compression stroke.
Valve clearance should be appropriate. Too large clearance could cause impact among valve, valve seat and
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other components, which will shorten their service life. it may also delay the valve open timing and advance the
valve close timing, thus shorten compression and exhaust time to reduce engine power. While too small valve
clearance will shorten the time to warm up components, valve can’t fully close, that also reduces engine power.
During the combustion, it could lead to the high-temperature gas leakage from the gap, overheaing or even burn
out valves.
During the course of operation, all factors could ficilitate clearnance change including worn-out parts,
loosened adjusting screw, overhauled cylinder head or parts and retightening of cylinder head nuts. Therefore, it is
required to check and adjust the valve clearance regularly.
The intake / exhaust valve (cold state) clearance of a turbocharged diesel engine is 0.35 mm ± 0.05 mm. If it
changes during the practical use, check and adjust it in accordance with the following procedures.
(1) Turn crankshaft till 1
st
cylinder piston reaches TDC of compression stroke, saying pulley TDC mark “0”
aligns the pointer on gear cover, and intake/exhaust valves in 1
st
cylinder are both closed (see Figure 8-10).
Perform adjustment on 1,2,3,5 valves(see Figure 8-11).
Figure 8-11 Adjustment of Valves No. 1, 2, 3 and 5
(2) Insert a feeler into rocker arm and valve (see Figure 8-12), and loosen concerning rocker arm locking nut,
turn adjust screw with a screwdriver till feeler becomes snug. Then retighten the nut
Figure 8-12 Check the Valve Clearance Using a feeler
Front
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(3) After adjustment is done, turn crankshaft 360 degree. At the moment, 4
th
piston is at its TDC of
compression stroke. Perform same adjustments on remaining 4,5,7,8 valves.
8.2.14 Check the Turbocharger before Installation
Remover a new turbochanger’s external packaging to check if its rotor rotates freely. If there are impacting
sound or rotation lagging, find out the reasons and install it only after troubleshooting.
Check and clean the air filter element. Replace paper element in accordance with the technical requirements.
Check and clean compressor intake pipe and engine exhaust pipes. Keep any foreign objects off from
turbocharger.
Check the oil filter and replace contaminated and damaged.filter element
Check and clean turbocharger’s oil supply and return pipes to ensure it is clean without distortion. The shims
for oil supply and return pipes are not allowed to block off the oil supply / return holes in turbocharger.
Check oil and change diry or deteriorated oil.
8.2.15 Installation of Turbocharger
The turbocharger should be secured reliably. The tightening torque of the exhaust pipe nut connecting to the
turbocharger should be 28 – 35 Nm, and the oil inlet / return pipe should be connected reliably. When to install the
oil inlet/return pipe, do not apply the sealant on the joint to avoid the entrance of the sealant into the turbocharger
and thus prevent the parts and components from be damaged.
Secure the double-steel-wire clip used to fix turbocharger’s rubber connection hose, avoid air leakage which
causes the power down.
After a new turbocharger is installed on the diesel engine, refill the clean engine oil through the oil filler
opening, turn the rotor by hand to pre-lubricate the turbocharger.
8.2.16 Check and Adjust the Turbocharger
Adjust the relative angle of turbocharger housing:
(1) Unscrew the bolt securing the compressor casing (or turbine casing), keep oil return opening on the
intermediate casing downward vertically, and turn the compressor casing (or turbine casing).
● Caution: DO NOT fully unscrew the bolt to avoid the impeller contacts with the casing.
The torque of compressor casing bolts should be 5.7 N·m,
The torque of turbine casing bolt should be 11.3 N·m.
(2) If necessary, check the operating condition of the turbocharger rotor. Turn the rotor by hand, a normal
rotor can rotate by itself at least one turn. Dismantle to check faulty turbocharger. Rotor check needs absolute tidy
operating environment to keep foreign object from entering the turbocharger..
Use the special equipment and tools to disassemble and reassemble the turbocharger assembly. As only the
turbocharger manufacturer and service center (station) have these special equipment and tools, user is not
suggested to perform these operations by himself unless it has to.
(3) Disassemble the compressor casing and check for oil leakage. At the same time, clean the inside
chamber of compressor casing and the surface of compressor impeller. Special care should be taken to protect
impeller during cleaning.
8.2.17 Adjust Advance Angle of Fuel Injection Pump (Stationary State)
The optimal fuel supply advance angle of a diesel engine is preset by the manufacturer. The advance angle
of fuel injection pump should be 8º - 12º CA before top dead center (crankshaft angle)of compression stroke. In
winter, the angle can be adjusted up to its upper limit while down to its lower limit in summer.
The improper advance angle will influence engine’s power, fuel consumption and normal operation. Adjust
any improper advance angle as per following methods:
(1) Check the advance angle of fuel injection pump (stationary state)
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Loosen the No 1 cylinder’s high pressure fuel pipe nuts, turn the crankshaft counter-clockwise and stop
turning at the moment fuel drips from the piston in No 1 cylinder. In this case, the scale reading on crankshaft
pulley that aligns with pointer on gear chamber cover is the value of advance angle. The scale readings are 6º, 8º ,
10º, 12º, 14º and 16º respectively.
(2) Adjust advance angle of fuel injection pump (stationary state)
If the advance angle checked above doesn’t conform to the specified value, loosen three nuts on injection
pump, move the injection pump slightly inward or outward. Advance angle decreases as it moves inward while
advance angle increases as it goes outward. When the advance angle of fuel supply reaches its ideal position,
tighten the above mentioned three nuts, and finally, check again whether or not the adjusted advance angle of fuel
supply is proper.
● Caution: It is not allowed to dismantle the parts with lead seal on injection pump. Approach to
professional help. And if necessary, conduct the testing and adjustment on the special test stand.
8.2.18 Check Fuel Injector
The turbocharged diesel engine adopts the S series multi-orifice injectors, Model CKBEL87S069 or ZP22
(see Figure 8-13). It atomizes the fuel and sprays into combustion chamber where fuel mist mixes with the air and
become combustible mixture.
Figure 8-13 Fuel Injector Assembly
1-Injector; 2-O-ring; 3-Copper washer
Malfunction of a fuel injector will lead to uneven engine Rpm and black smoke emitting. In order to find
which injector is faulty, you should set throttle on a position where engine Rpm is most irregular, unscrew high
pressure pipe joint nuts on fuel injection pump top to shut off fuel supply to relevant cylinder. If the engine Rpm
does not change much at a cylinder whose fuel has been cut off while engine emits less smoke, injector in this
cylinder must be faulty and should be removed.
8.2.19 Replace Fuel Injector
● Caution: DO NOT let the contaminated material and dirt enter the fuel system. Before disconnect the
connector, thoroughly rinse the jointing area. Use appropriate goods to cover the connector that has been opened.
(1) Disassemble the fuel return pipe.
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(2) Disassemble the high pressure fuel pipe connecting nuts from the injector and injection pump. Do not
bend the fuel pipe, and if necessary, disassemble the return pipe clamp.
(3) Remove retaining screw, and detach the clip, injector, O-ring, injector washer. Install new O-ring and
injector washer on the new injector.
(4) Mount the new injector, O-ring and injector washer. Put on pipe clamps and retaining screw. Ensure the
injector does not tilt. Evenly and gradually tighten the retaining screws.
● Caution: Tighten high pressure pipe connecting nuts with specified tightening torque. If any leakage
occurs around nut, check whether the fuel pipe is correctly aligned with the inlet of injector. DO NOT over-
tighten the injector connecting nut, otherwise fuel pipe end will be crashed, thus fuel supply is affectd.
(5) Install the high pressure pipe and tighten the connecting nut.
(6) Replace the sealing gasket and install the fuel return pipe, tighten the blots.
(7) Start the diesel engine, and check for fuel and air leakages.
8.2.20 Check the fuel injection quality of the injector
Check injecting quality. Put a fuel injector on test stand to observe its spraying quality. Clean, adjust and
even replace injector in the events of poorly atomization, fuel spills, leakage and strange injecting sound (see
figure 8-14).
A normal injecting quality is identified with following conditions: fine fuel mist; a certain cone angle
(between 4-12°); clear sound of “pop, pop…”; clear and quick fuel shutoff; no dripping or leaking after injecting.
Moisture at injector tip is allowed.
● Caution: Do not go on using an injector which fails to satisfy the technical requirements. Replace it with a
new one
8.2.21 Check the Injection Pressure of the Injector
All injectors in a new diesel engine has been checked and adjusted in the factory, users can directly use it
without readjustment. However, after the diesel engine has operated for a period of time, injector spring elastic
force will change, that makes injector pintle opening pressure changing. In addition, chenk ther pressure after
injector had been removed and cleaned.
Check the injection pressure of injector on a test bench: secure injector on the test bench, disassemble the
fuel pipes, at this momnet pressure gauge indictates “0” . Pump the fuel and observe pressure gauge indication.
Check whether pressure gauge indicates specified value (20 – 21 MPa).
Figure 8-14 Check the Injection Quality of an Injector Using a Test Bench
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8.2.22 Regulation of Injector Opening Pressure
The opening pressure of a injector in turbocharged diesel engine is regulated by increasing and decreasing
the thickness of the pressure regulating shim to injector body. Increase the thickness of shim to raise the opening
pressure; and decrease the shim thickness to reduce the opening pressure.
If it is required to regulate the injection pressure, operator should clean the outside of injector and unscrew
the tightening nuts. Note that the coupling parts, tappet, springs and original washer should not be discarded. Keep
all part and component clean.
8.2.23 Check the Thermostat
Thermostat automatically changes coolant flow in radiator according to engine temperature to maintain
engine in a proper operation temperature. (figure 8-15)
The temperature sensing element of the thermostat is a paraffin-type one. The thermostat is installed in the
thermostat casing at the water outlet on the cylinder head.
Figure 8-15 A Thermostat
Figure 8-16 Thermostat Test
1-Thermometer; 2-Water under Heating; 3-Thermostat
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A bypass valve under thermostat closes when thermostat valve opens, coolant then flows into radiator to
improve cooling. The thermostat valve closes when water temperature is low, and then the bypass valve opens to
cut off the passage from the water jacket to the radiator, and the coolant enters the water pump through the bypass
pipe and then is driven back to the water jacket. In this case, the coolant doesn’t go through the radiator, it
circulates only between the water jacket and water pump. This small circulation could help to warm up diesel
engine quickly. When coolant temperature is high, thermostat valve will fully open, the minor circulating bypass
valve is closed at the same time to let coolant flow into the radiator and conduct the major circulation to improve
heat dissipation.
Thermostat initial opening temperature is 76℃±2℃, full opening temperature is 90℃. Full opening travel
is no less than 8mm.
Test thermostat: remove thermostat, put it into a container with water to warm it up gradually. Observe
temperature with a thermometer. While water temperature is changing, check if valve closes or opens as
requirements (see figure 8-16). Otherwise replace thermostat.
Figure 8-17 Check and adjust water pump belt tension
8.2.24 Adjust Belt Tension
Fan belt tension should be proper. If it is too loose, the belt will slip over the belt pulley. This would decrease
fan speed to affect cooling system performance and speed up belt wear. While too tight belt would facilitate
bearing wear and increase power consumption.Check the belt tension regularly.
Install the belt into alternator and water pump belt pulley groove first, then into the crankshaft pulley
groove. To tighten the fan belt, turn the alternator outward, and tighten the fastening bolts.
Check fan belt tension after a diesel engine has operated up to 100h (vehicle milieage 4,000~ 5,000 km).
Hand press the belt (70 ~80 N ) at the spot between the water pump and alternator pulle. Its deflection should be
preferentially 6~8 mm (see Figure 8-17).
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Chapter 9
Diesel Engine Faults and Troubleshooting
During diesel engine operation, technical state of the parts could deteriorate gradually due to wearing,
distorting and improper maintenance. When some technical indices exceed the limits, the engine is faulty. The
common faults on a diesel engine are: hard start-up, rough operation, lack of power, abnormal sound during
operation, abnormal exhaust gas color, lower oil pressure and higher coolant temperature, etc.
Remove any engine faults whenever they happen. Engine operates with faults would reduce its power and
economy and deteriorate its operating performance. Moreover, it would accelerate parts wear or lead to accidental
damages.
● Notes:
(1)Diagnose an engine according to symptoms and by referring to diesel engine’s construction /operation
theories. Avoid missing a fault or dismantling blindly.
(2)Much complicated diagnosis or fault-removing procedures may need to use instrument or special
equipment, and be performed by technician.
The diesel engine faults and removing procedures in this chapter are for reference only.
9.1 Hard start-up
Symptoms and causes
Removing procedures
Wrong circuit connection or poor
contact
Check if connections are tight and reliable.
Weak battery
Charge battery
Poor contact between start brush
And commuter
Repair or replace brush. Polishing commuter surface with wooden
sandpaper and blow it clean
Stuck or failure starter solenoid
Adjust solenoid and replace if necessary
Electrical
system
Failure pre-heating system
Replace glow plug
Air in fuel system
Check if fuel supply connector is loose. Loosen vent screws on
injection pump and fuel filter, press hand pump till no bubble in
overflowed fuel. Retighten vent screws and hand pump.
Choked fuel pipe
Check if fuel pipe is clear.
Blocked fuel filter
Clean fuel filter or replace element.
Fuel pump failure or inconsistent
supply
Check fuel inlet pipe for air leaking and if screen net is blocked. If
there is no fuel supply after removing faults, check fuel inlet pipe
and fuel pump.
Less injection from injector. No
injection or non atomization
Check injector for its atomizing state, check to see if injector
plunger and oil outlet valve is worn-out or stuck, check and adjust
the injection pressure to specified range.
Fuel
system
No fuel supply from injection
pump
Check and repair.
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Symptoms and causes
Removing procedures
Worn-out piston compression
ring
Replace piston ring. And replace cylinder sleeve as per its wear
situation.
Mechanical
system
Leaked valve
Check valve and valve seat for air sealing. Repair or grind if
necessary.
9.2 Hard start-up at low temperature
Symptoms and causes
Removing procedures
Fuel
In winter or cold area, diesel becomes
turbid and frozen due to selection of
wrong fuel.
Use low-freezing diesel according to local ambient
temperature
Oil
In winter or cold area, selecting
wrong oil. Oil becomes too viscous,
which increase interior friction and
the resistance to start-up.
Use low-viscosity oil according to local temperature of the
diesel engine in order to decrease the starting power.
Battery
Select to use battery whose volume is
less than 100Ah in cold area or in
winter
Select to use low-temperature battery whose volume is
larger than 100Ah according to local temperature
9.3 Insufficient power
Insufficient diesel engine power means engine power does not reach the designed requirements. Engine is
“weak” and tends to stalling under heavy load or climbing a hill. The lack of power usually comes with hard start
up. They are related to each other, cross-reference diagnosing can be made thereupon.
Symptoms and causes
Removing procedures
(1)air in fuel pipe and fuel filter, or
they are blocked.
Bleed the system or replace fuel filter element, flush oil
pipes.
( 2 ) insufficient fuel supply from
injection pump.
Check, repair or replace plunger sets.
Power and
Rpm do not
increase
after
depressing
gas pedal
Fuel injector atomization is poor or
injecting pressure is low and some fuel
injectors are stuck.
Check fuel injector atomization or adjust injecting
pressure. Check, repair or replace injector parts.
Blocked air filter
Remove dust on air filter element. Replace if necessary.
Bad exhaust
gas color
with higher
temperature
Exhaust pipe has longer connector or
connecting pipes, small turning radius
or to many elbows.
Remove carbon deposit inside the exhaust pipe, re-install
exhaust connecting pipes, use less than 3 elbows with
enough exhausting section.
Fuel supply advance angle and valve
timing are changed.
Check and adjust the static fuel supply advance angle and
valve timing.
Poor
performance
at each gear Valve clearance is changed.
Check and adjust the valve clearance.
Coolant temperature is too high.
Check cooling system, remove water scale; check belt
tension and adjust it if necessary; check thermostat.
Oil temperature is too high.
Check oil volume and add if necessary; if bearing and any
motion parts get hot, find out the cause and remove
Diesel
engine
overheating
Exhaust gas temperature is too high.
Check and correct static fuel supply advance angle and
fuel injector injecting pressure
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Chapter 9 Diesel Engine Faults and Troubleshooting
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Symptoms and causes
Removing procedures
Leakage at contacting face between
cylinder head and block. Cylinder-head
bolt is loose or the cylinder-head gasket
is damaged.
Tighten cylinder head as per specified torques, or replace
cylinder-head gasket.
Leakage at intake/exhaust valves
Disassemble and check intake/exhaust valves, grind
contacting face between valve and valve seat. Replace
parts if necessary.
Valve clearance is not correct.
Adjust valve clearance to standard.
Lack of
power,
performance
deteriorates,
leakage,
black smoke
and
abnormal
slapping.
Leakage at injector hole, or copper
washer is damaged
Remove to check injector. Clean injector hole and replace
damaged parts.
9.4 Abnormal noise during operation
First of all, operator should recognize what a abnormal sound is like: either a knock due to an abnormal
breaking-out or clashing noise due to parts’ abnormal motion. Diagnose to locate sound source according to its
acoustic feature together with parts construction theory.
●Cautions: It is strictly prohibited to keep a diesel engine operating with abnormal noise. Once hearing an
abnormal noise, you should stop vehicle immediately to check and remove the fault to avoid accident.
Symptoms and causes
Removing procedures
Early injecting or fuel injector is stuck, there is clear
metal-beating noise in the cylinder.
Adjust static fuel supply advance angle, and check fuel
injector for injecting.
Excessive clearance between piston pin and connecting
rod small end bushing hole, which makes light and
sharp noise. The noise is clearer during idle running,
and turns sharper when throttle is opened wider
suddenly.
Replace connecting rod small end bushing to make its
clearance reaching the standards
Excessive clearance between piston and cylinder
sleeve, and clashing noise can be heard from engine
outside. The noise gets louder with rising of engine
Rpm.
Replace piston, piston ring. Or replace cylinder sleeve
depending on its wear.
Excessive clearance between connecting rod bearing
and main bearing due to wear. Clashing noise among
engine parts can be heard at crankcase during
operation. And heavy and strong knocking can be heard
when engine Rpm is slowed down suddenly.
Disassemble to check bearing. Replace it if necessary.
And keep specified fitting clearance.
Valve knocks piston. Heavy, even and rhythmical
beating noise can be heard at cylinder head.
Find out knocking cause, check valve timing, and
adjust valve clearance.
Drive gear is worn-out or with excessive clearance.
Abnormal noise comes out from gear chamber. And
knocking noise can be heard at sudden deceleration.
Check driving gear clearance and replace gear if
necessary.
Excessive clearance at intake/exhaust valves. Louder
and rhythmical sound can be heard at cylinder head.
Re-adjust valve clearance.
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9.5 Abnormal exhaust gas color
The color of exhaust gas under normal load is light gray, and deep gray for the most under short heavy load.
Blue, white or black gas indicates faults are occurring. Blue indicates oil burning; white indicates that atomized
diesel have not burnt in cylinder or there is water in the fuel; and black indicates the injected fuel is excessive,
which has not burnt completely.
Symptoms and causes
Removing procedures
Diesel operates under overload.
Reduce diesel engine load to specified range.
Uneven fuel supply among cylinders
Adjust fuel supply to each cylinder from injection
pump.
Incorrect valve clearance, poor valve
sealing (exhaust valve is leaking)
Adjust valve clearance and check sealing cone.
Smaller fuel injecting angle, injecting
delay causes part fuel burning in exhaust
pipe.
Adjust static fuel supply advance angle.
Insufficient air intake, air filter or intake
pipe is blocked.
Remove dust and dirt, and replace air filter element if
necessary.
Worn-out cylinder sleeve and piston ring. Replace parts.
Black
exhaust
gas
Damaged EGR system solenoid (for
diesel engine with EGR system only)
Disconnect the hose (from solenoid) from EGR valve
end, if black smoke stops, it shows solenoid has
damaged and needs to be replaced.
There is water in cylinder or in diesel.
Locate the cause and remove.
White
exhaust
gas
Engine is too cold at cranking, no
combustion in certain cylinder (especially
in winter).
Increase moderately engine Rpm and load and let it
run longer.
Piston ring is stuck or worn-out, and its
elasticity becomes poor. Oil enters
combustion chamber as second piston ring
has been mounted on wrong side.
Disassemble and check piston ring, or replace it if
necessary.
Engine operates on low load for a long
period, clearance between piston and
cylinder sleeve becomes larger, oil enters
combustion chamber.
Increase moderately engine load or disassemble to
check or replace piston ring, piston and cylinder
sleeve.
Blue
exhaust
gas
Excessive oil in oil pan.
Drain excess oil by referring to dipstick hole.
9.6 Low oil pressure
Each diesel engine’s high-speed moving sets should get enough lubricant to reduce wearing and taking heat
away. This will help to avoid parts from stuck and early worn-out. Moreover, lubricating oil can fill up the tiny
clearance in parts (e.g. the one between piston and inner wall of cylinder sleeve), which will improve sealing and
prevent high-pressure air leak, making start-up easy and keeping engine’s original power. Therefore, lubricating
oil should have certain pressure and flow, and should be clean as well.
●Cautions: Engine oil pressure lower than specified value indicates there is fault in lubricating system.
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Chapter 9 Diesel Engine Faults and Troubleshooting
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Never run diesel engine without oil pressure or under lower oil pressure. In those cases, one should shut off engine
to check and remove faults.
Symptoms and causes
Removing procedures
Oil pressure meter indication does not match sensor
output.
Replace them in pair with mated ones from same
manufacturer.
Oil amount in oil pan is not enough.
Add oil to specified level.
Oil strainer or filter is blocked, or filter pressure
adjusting valve is failure.
Clean oil strainer, replace oil filter element, and adjust
or replace pressure-adjusting valve.
Oil pump pressure limiting valve is failure.
Adjust or replace oil pump pressure limiting valve.
Fitting clearances at connecting rod bearing,
crankshaft bearing and camshaft bearing are
excessive.
Replace with new bearing.
Oil pump is worn-out severely or there is other fault
inside.
Check, adjust or replace relevant parts.
Oil viscosity is much low.
Change with specified oil.
9.7 Abnormal coolant temperature or coolant short
Symptoms and causes
Removing procedures
Diesel engine
overheating
(1)Coolant level is too low
(2)Fan belt is loose or broken
(3)Thermostat main valve stuck
(4)Faulty water pump and fan
clutch
(5)Incorrect fuel supply timing
(6)Chocked radiator core
(1)Replenish coolant, check for leak, repair if necessary
(2)Adjust fan belt tension or replace fan belt
(3)Replace thermostat assembly
(4)Replace water pump and fan clutch
(5)Correct fuel supply timing
(6)Clean radiator
Diesel engine
is too cold
(1)Thermostat valve is ajar
(2)Coolant temperature meter is
failure
(1)Replace thermostat
( 2 ) Measure coolant temperature, replace coolant
temperature meter
Short coolant
often
(1)Radiator is leaking
(2)Radiator hose connector is
loose or hose is damaged
(3)Water pump is leaking
(1)Repair or replace radiator
(2)Tighten clamp or replace hose
(3)Replace water pump assembly
●Notes:
(1)Once a diesel engine gets overheated, it is not allowed to shut down engine or add coolant immediately.
Run engine under no-load at mid-large throttle opening till coolant temperature drops. Then stop engine to
perform checks.
(2)Do not remove radiator cap while engine is still hot to avoid scalding. Use caution when adding coolant.
(3)In the event the cause of overheating cannot be found, contact service station or repairing garage
immediately to prevent other parts from damaged.
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OPERATION AND MAINTENANCE MANUAL FOR FOTON VIEW SERIES LIGHT BUS
·150·
9.8 Supercharging system faults
Symptoms and causes
Removing procedures
Lack of
power
(1) Impurity deposits at sealing location on turbine side
(2) Higher oil temperature, insufficient fuel supply and
floating bearing is burnt
(3) Oil leaks from turbine and compressor shaft end due to
blocked or distort oil return pipe.
(4) Supercharger sealing ring is failure due to damage
(5) Turbine rotor lost balance
(6) Turbine and compressor impellers are worn-out and
damaged.
(7) Air filter is blocked (dirty).
(8) Boost compensator breaks air pipe
(9) Dirty intake/exhaust pipes or connectors are leaking.
(10)Supercharger cannot operate well or is damaged.
(1) Change
oil
and
service
supercharger.
(2) Check fuel supply system,
service supercharger.
(3) Service and replace fuel
return pipe.
(4) Replace sealing ring.
(5) Repair and replace turbine
shaft rotor
(6) Check and service.
(7) Service air filter and replace
element
(8) Check
or
replace
air-conducting pipe.
(9) Clean,
check,
repair
or
replace air intake/exhaust
pipes
(10)
Check, repair or replace
supercharger
Higher fuel
consumption
(1)Dirty intake/exhaust pipes or air leak at connections.
(2)Poor supercharger performance
(1)Check or replace part.
(2)Clean, adjust or replace.
Higher oil
consumption
(1)
Supercharger sealing ring is worn out.
(2)
Oil leakage at compressor impeller end.
(3)
Screws at joints of oil intake / return pipe are loose
washers are damaged.
(4)
Oil is of poor quality.
(1) Replace sealing ring.
(2) Check and repair.
(3) Check,
repair
or
replace
washers.
(4)Change
oil
according
to
requirements.
Abnormal
noise
(1) There is too much oil dirt in gas passage on turbine
end, which narrows the passage.
(2) There is too much oil dirt in gas passage on
compressor end, which narrows passage.
(3)Excessive wear on floating bearing, rubbing between
turbine/compressor impeller and case.
(1) Clean or replace.
(2) Clean or replace.
(3) Replace floating bearing.
Vibration due
to rubbing
between
turbine, air
compressor
impeller
(1) Foreign matter enters.
(2) Floating bearing is excessively worn out.
(3) Poor turbine shaft dynamic balance.
(1)Clean or replace.
(2)Replace floating bearing.
(3)Check, repair or replace.
● Cautions:
(1)Be ware of any foreign matters entering intake/exhaust system during fault removing and assembling /
disassembling a diesel engine. Supercharger rotor rotates at a very high speed, its clearance to case is narrow, any
foreign matters either big /small or soft / hard would adversely affect rotor performance and damage its impellers.
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Chapter 9 Diesel Engine Faults and Troubleshooting
·151·
The supercharger may subject to abnormal vibration and noise once the impellers are damaged. Shut off engine
immediately when this happens, perform check and repair on supercharger.
(2)Oil leak on supercharger does not warrant that it must be replaced as long as impeller does not rub case
and impeller shaft can rotate freely. Supercharge in this case can be used after oil leak has been removed.
9.9 Starter does not run, weak startup and noise
Symptoms and causes
Removing procedures
Starter motor does
not run
(1) Starter switch and other control circuit are
disconnected.
(2) Poor
contact
between
brush
and
commutator
(3) Starter motor internal disconnected
(1) Check circuit, make connections
reliable.
(2) Adjust brush spring pressure, clean
the commutator.
(3) Check and repair starter.
Weak starter,
cannot startup
diesel engine
(1) Lower battery volume
(2) Poor lead contacting
(3) Burnt damage or oil dirt on commutator
surface.
(4) Worn-out brush or weak brush spring leads
to poor brush contacting with commutator
(5) Poor contacting due to burnt electro-
magnetic switch main contacts,
(6) Worn-out bearing, armature rubs case
(1)Charge
battery
according
to
specifications.
(2)Tighten lead connections.
(3)Polish the commutator surface or
remove the oil filth.
(4)Replace carbon brush or adjust carbon
brush spring.
(5)Polish with grade “0” non-metallic
sandpaper.
(6)Replace bearing.
Engine started
up, while starter
goes on running
with sharp
noise
(1) Bronze contact disk sticks to two contacts
inside starter clutch
(2) Starter motor armature shaft is bent.
(3) Tooth face is scratched to be stuck.
(4) Starter overriding clutch is damaged.
(1)Cut off power immediately, check
circuit and repair contacts.
(2)Cut off power immediately, replace
starter
(3)Cut off power immediately, repair
tooth face.
(4)Cut off power immediately, repair or
replace clutch.
9.10 Alternator does not work, lower/higher charging current
Symptoms and causes
Removing procedures
Alternator does not
work
(1)Wrong circuit connection, disconnected
circuit or poor contacting.
(2)Rotor coil is disconnected.
(3)Commutator diode is damaged.
(4)Poor contacting on carbon brush.
(5)Regulator is damaged.
(1)Check and repair circuit.
(2)Check repair or replace alternator
assembly
(3)Replace commutator diode.
(4)Remove dirt on brush or replace brush.
(5)Repair or replace regulator.
Lower charging
current
(1)Driving belt is loose.
(2)Regulated voltage is too low.
(3)Battery fluid is insufficient or the battery
plates are severely sulphurized.
(1)Adjust belt tension.
(2)Replace regulator.
(3)Add battery fluid to specified level.
Replace battery with severely sulphurized
plates.
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