73 

 
No. 042 Oil pump with abnormal sound   

Malfunction Causes 

Solution 

 

Engine oil not sufficient   

Check oil level within crankcase; if too low, fill up to 
standard height;   

Engine oil with poor quality   

Replace engine oil;   

Filter screen blocked   

Check filter screen is blocked; if so, clean or replace; 

Clearance of driving gear of oil pump too large 

Check clearance; if necessary, replace it;   

Oil pump sounding   

When at idling speed, probably oil pan position 
appearing with clear clattering; if necessary, replace 
oil pump;   

Valve blocked   

Check and clean;   

Driving gear of oil pump sounding   

Fit clearance between driving gear of oil pump and 
driving gear of camshaft changes, thus damaging 
driving gear of oil pump;   

Engine bottom 
with regular 
clattering 

JL376/378 driving chain sounding   

Replace driving chain;   

 

Add 

Oil pump with abnormal 
sound

Engine oil not sufficient 

Engine oil with poor 
quality 

Filter screen blocked 

Clearance of driving gear of oil 
pump too large 

Oil pump sounding 

Valve blocked 

Driving gear of oil pump 
sounding 

Driving chain 
sounding 

Replace

 

Replace 

Clean 

Replace 

Repair 

Replace 

Clean 

Normal 

Insufficient 

Normal 

Normal 

Normal 

Normal 

Normal 

Normal 

Poor

Blocked

Large clearance

Sounding

blocked

Sounding

Sounding

 
 

 

 

74 

 
No. 043 Crankshaft thrust piece with abnormal sound   

Malfunction Causes 

Solution 

 

Engine oil not sufficient   

Check oil level within crankcase; if too low, fill up to standard height; 

Engine oil with poor quality   

Replace engine oil;   

②

Check filter screen is blocked; if so, clean or replace;   

Engine oil with too low pressure   

C

③

heck clearance between drive gear and driven gear of oil pump. 

And check relief valve is blocked; if so, repair or replace; 

Crankshaft and thrust piece severely 
worn  

Crankshaft and thrust piece severely worn, causing too large axial 
play, and abnormal sound; disassemble the engine and repair;   

Thrust piece burnt and damaged 

Check it is burnt and damaged; if necessary, replace thrust piece; 

Crankshaft thrust 
piece with 
abnormal sound 

Thrust clearance too large   

Measure thrust clearance at thrust piece, with standard value as 
0.087mm-0.177mm; if exceeding limit value 0.300mm, replace 
thrust piece. (empirical value) 

 

Replace 

Crankshaft thrust piece with 
unusual noise 

Engine oil not sufficient 

Engine oil with poor 
quality 

Engine oil with too low pressure 

Crankshaft and thrust piece severely worn 

Thrust piece burnt and 
damaged

Thrust clearance too 
large 

Repair 

Replace 

Replace 

Repair 

Add 

Normal 

Large clearance

Normal 

Normal 

Normal 

Normal 

Burnt and damaged

Worn

Too large

Poor

Insufficient

 
 

 

 

75 

 
No. 044 Valve with abnormal sound   

Malfunction Causes 

Solution 

Valve clearance too large   

Remove valve chamber cover, and make the engine run at idling speed; 
listen to the sound and observe splashing of lubricating oil, and make 
preliminary judgment; insert feeler gage to suspected valve clearance; if the 
sound weakens or disappears, then it is this valve that is sounding; with the 
engine under cold state, adjust valve clearance; when clearance of intake 
valve is 0.12mm~0.15mm, corresponding exhaust valve clearance is 
0.20mm~0.25mm. when adjusting, make the valve closed;   

Engine oil not sufficient 

Check oil level within crankcase; if too low, fill up to standard height; 

Cylinder cover deformed   

Replace cylinder cover;   

Check oil screen is blocked; if so, clean or replace;   

Check clearance between drive gear and driven gear of oil pump. And 
check relief valve is blocked; if so, repair or replace;   

Engine oil with too low 
pressure, poor lubrication 
causing abnormal sound 

Check clearance between crankshaft and connecting rod tile is too large 
causing oil leaking too much and oil pressure too low;   

Continuous, regular 
and clear “da-da” 
sound is heard at 
one side of valve 
chamber. When the 
engine is at idling, 
medium speed, the 
sound becomes 
obvious; when high 
speed, the sound is 
in disorder. This 
sound is not 
affected by engine 
temperature and 
flameout. 

Camshaft worn   

If abnormal sound still exists after adjustment of valve clearance, check and 
measure cam lobe is damaged or severely worn; if exceeding limit value 
0.300mm, replace it. (empirical value) 

 

Valve clearance too large 

Engine oil not 
sufficient 

Cylinder cover 
deformed 

Engine oil with too low pressure, poor lubrication 
causing unusual noise 

Camshaft worn 

Valve with abnormal 
sound 

Adjust 

Replace 

Add 

Repair 

Replace 

Normal 

Worn

Normal 

Normal 

Normal 

Poor

Deformed

Insufficient

Too large

 
 

 

 

76 

 
No. 045 Engine with insufficient power   

Malfunction Causes 

Solution 

 Check air filter is blocked; if so, clean or replace; 

①

 

 Air filter blocked 

①

 

 Check intake system is leaking. Measure degree of vacuum 

②
of intake manifold. When at idling speed, degree of vacuum 
shall be larger than 30KPA; if too small, it indicates that intake 
system is leaking; carefully check connection and each hose, 
vacuum pipe;   

 Step on accelerator pedal to the bottom, and check throttl

③

e 

valve is fully opened; if not, adjust its dragline or pedal;   

②

    Throttle valve tie-line or throttle valve 

position sensor improperly adjusted, and 
could be fully opened 

 Check throttle valve position sensor. When throttle valve is 

③
changed from fully closed to fully opened, resistance of its 
signal terminal and earthing terminal shall be increased 
continuously, without interruption; if unusual, adjust or replace it 
accordingly;  

③

  Improper ignition timing or weak 

high-pressure spark   

⑤

Check ignition timing. When the engine is at idling speed, 

ignition advance angle is 10°--12°; if not correct, adjust advance 
angle of initial ignition of the engine. When accelerating, ignition 
advance angle could automatically be increased to 20°--30°. If 
unusual, check ignition control system or replace ECU; 

Fuel pressure too low

④

 

 Check fuel pressure. When at idling s

⑥

peed, fuel pressure 

shall conform to specified value 265~304kpa. When 
accelerating, fuel pressure shall increase about 50kpa. If too 
low, check fuel pressure adjuster, electric fuel pump, gasoline 
filter, etc;   

⑤

  Oil injector blocked or with poor 

atomization 

 Remove oil injector; check ejecting amounts and atomization 

⑦
are normal; if not, clean or replace oil injector;   

⑥

    Battery voltage too low 

 Check battery voltage is normal; if too low, it will cause 

⑧
reduced ejecting amounts, causing insufficient dynamic force, 
and slow acceleration; if too low, check charging system or 
replace battery;   

⑦

  Cooling liquid temperature sensor 

malfunction 

 Check cooling liquid temperature sensor. Resistance of this 

⑨
sensor could be changed according to specified standard under 
different temperatures; if not, replace this sensor;   

⑧

    Inlet pressure sensor malfunction   

 Check intake manifold pressure temperature sensor; if 

⑩
unusual, replace it;   

The engine is 
basically running 
normally without 
load; but 
accelerating slowly 
and hard to grade 
up with load; when 
stepping on 
accelerator pedal 
to the bottom, still 
feels that power is 
not enough, 
rotating speed 
could not be 
increased, and 
unable to reach 
maximum speed.   

Engine cylinder pressure too low

⑨

 

 Measure compression pressure of e

⑾

ngine cylinder; if too low, 

adjust valve clearance or remove the engine;