161 

No.119 Difficulty startup at any time though with normal speed   

General malfunction part: 1. fuel containing water; 2. fuel pump; 3. cooling liquid temperature 
sensor;4. oil injector; 5. ignition coil; 
6. throttle valve body and idling speed bypass duct; 7.intake duct; 8. ignition timing; 9. spark 
plug;10. mechanical parts of engine. General diagnosis flowchart: 

Serial No.  Operation steps 

Results   

Follow-ups   

Yes 

Repair air intake 
system 

1 

Check air filter is blocked, and intake duct is air leaking. 

No Next 

step 

Yes Next 

step 

2 

Connect fuel pressure gauge (access point is front end of oil sucker of 
fuel distribution pipe assembly), and start the engine, and check fuel 
pressure is around 350kPa. 

No 

Repair oil supply 
system 

Yes Next 

step 

3 

Take out line of one cylinder, and connect spark plug, making spark plug 
electrode about 5mm away from engine body. Startup the engine and 
check there is high pressure spark. 

No 

Repair ignition 
system 

Yes Next 

step 

4 

Check spark plug of each cylinder, and observe its type and clearance 
conform to the specifications. 

No 

Adjust or replace 

Yes 

Repair lines or 
replace sensor 

5 

Take out connector of cooling liquid temperature sensor, start the engine 
and observe it is successfully started at this time. 

No Next 

step 

Yes 

Clean throttle valve 
and idling speed 
duct 

6 

Step on the throttle lightly, and observe it is easily started. 

No Next 

step 

Yes 

Replace 
malfunctiony ones 

7 

Remove oil injector, and check it is leaking or blocked with special 
cleaning and analysis instrument. 

No Next 

step 

Yes Replace 

fuel 

8 

Check fuel condition and observe malfunction is caused just after 
refueling.   

No Next 

step 

Yes 

Eliminate 
mechanical failure 

9 

Check pressure of each cylinder of the engine, and observe engine 
cylinder is with insufficient pressure. 

No Next 

step 

Yes Next 

step 

10 

Check ignotion sequence and ignition timing of the engine conform to the 
specifications. 

No 

Repair ignition 
timing 

Yes Diagnosis 

help 

11 

Connect commutator of electric injection system, and open ignition 
switch, and check power supply of 12#, 13#, 44#,  45#, ,63# pins are 
normal; check bonding of 3#, 51#, 53#, 61#, 80# pins are normal. 

No 

Repair 
corresponding lines

 
 

 

 

162 

No.120 Normal startup with instable idling speed at any time   

General malfunction part:1. fuel containing water; 2. oil injector; 3. spark plug; 4. throttle valve 
body and idling speed bypass air duct; 5.

 

intake duct; 6. idling speed regulator; 7. ignition timing; 

8. spark plug; 9. mechanical parts of the engine. 
General diagnosis flowchart: 

Serial No.  Operation steps 

Results   

Follow-ups   

Yes 

Repair air intake 
system 

1 

Check air filter is blocked, and intake duct is air leaking. 

No Next 

step 

Yes 

Clean or replace 

2 

Check idling speed regulator is jammed. 

No Next 

step 

Yes Next 

step 

3 

Check spark plug of each cylinder, and observe its type and clearance 
conform to the specifications. 

No 

Adjust or replace 

Yes Clean 

 

4 

Check throttle valve body and idling speed bypass air duct is with carbon 
deposit. 

No Next 

step 

Yes 

Replace 
malfunction ones 

5 

Remove oil injector, and check it is leaking or blocked, or flow with out of 
tolerance with special cleaning and analysis instrument. 

No Next 

step 

Yes Replace 

fuel 

6 

Check fuel condition and observe malfunction is caused just after 
refueling.  

No Next 

step 

Yes 

Eliminate 
mechanical failure 

7 

Check pressure of each cylinder of the engine, and observe cylinder 
pressure has too large differences.   

No Next 

step 

Yes Next 

step 

8 

Check ignition sequence and ignition timing of the engine conform to the 
specifications. 

No 

Repair ignition 
timing 

Yes Diagnosis 

help 

9 

Connect commutator of electric injection system, and open ignition 
switch, and check power supply of 12#, 13#, 44#,  45#, ,63# pins are 
normal; check bonding of 3#, 51#, 53#, 61#, 80# pins are normal. 

No 

Repair 
corresponding lines

 

 
 

 

 

163 

No.121 Normal startup, with instable idling speed during warming up   

General malfunction part: 1. fuel containing water; 2. cooling liquid temperature sensor; 3. spark 
plug; 4. throttle valve body and idling speed bypass air duct; 5. intake duct; 6.idling speed 
regulator; 7. mechanical parts of engine. 
General diagnosis flowchart: 
 

Serial No.  Operation steps 

Results   

Follow-ups   

Yes 

Repair air intake 
system 

1 

Check air filter is blocked, and intake duct is air leaking. 

No Next 

step 

Yes Next 

step 

2 

Check spark plug of each cylinder, and observe its type and clearance 
conform to the specifications. 

No 

Adjust or replace 

Yes 

Clean concerned 
parts 

3 

Remove idling speed regulator, and check throttle valve body, idling 
speed regulator and idling speed bypass air duct are with carbon deposit. 

No Next 

step 

Yes 

Repair lines or 
replace sensor 

4 

Take out connector of cooling liquid temperature sensor, start the engine 
and observe the engine's idling speed is instable during warming up. 

No Next 

step 

Yes 

Replace 
malfunctiony ones 

5 

Remove oil injector, and check it is leaking or blocked, or flow with out of 
tolerance with special cleaning and analysis instrument. 

No Next 

step 

Yes Replace 

fuel 

6 

Check fuel condition and observe malfunction is caused just after 
refueling. 

No Next 

step 

Yes 

Eliminate 
mechanical failure 

7 

Check pressure of each cylinder of the engine, and observe cylinder 
pressure has too large differences.     

No Next 

step 

Yes Diagnosis 

help 

8 

Connect commutator of electric injection system, and open ignition 
switch, and check power supply of 12#, 13#, 44#,  45#, ,63# pins are 
normal; check bonding of 3#, 51#, 53#, 61#, 80# pins are normal. 

No 

Repair 
corresponding lines

 

 
 

 

 

164 

No.122 Normal startup, with instable idling speed after warming up   

General malfunction part:1. fuel containing water; 2.cooling liquid temperature sensor; 3. spark 
plug; 4. throttle valve body and idling speed bypass air duct; 5.intake duct;6. idling speed 
regulator; 7. mechanical parts of engine. 
General diagnosis flowchart: 

Serial No.  Operation steps 

Results   

Follow-ups   

Yes 

Repair air intake 
system 

1 

Check air filter is blocked, and intake duct is air leaking. 

No Next 

step 

Yes Next 

step 

2 

Check spark plug of each cylinder, and observe its type and clearance 
conform to the specifications. 

No 

Adjust or replace 

Yes 

Clean concerned 
parts 

3 

Remove idling speed regulator, and check throttle valve body, idling 
speed regulator and idling speed bypass air duct are with carbon deposit.

No Next 

step 

Yes 

Repair lines or 
replace sensor 

4 

Take out connector of cooling liquid temperature sensor, start the engine 
and observe the engine's idling speed is instable during warming up. 

No Next 

step 

Yes 

Replace 
malfunctiony ones

5 

Remove oil injector, and check it is leaking or blocked, or flow with out of 
tolerance with special cleaning and analysis instrument. 

No Next 

step 

Yes Replace 

fuel 

6 

Check fuel condition and observe malfunction is caused just after 
refueling.  
 
   

No Next 

step 

Yes 

Eliminate 
mechanical failure 

7 

Check pressure of each cylinder of the engine, and observe cylinder 
pressure has too large differences. 

No Next 

step 

Yes Diagnosis 

help 

8 

Connect commutator of electric injection system, and open ignition 
switch, and check power supply of 12#, 13#, 44#,  45#, ,63# pins are 
normal; check bonding of 3#, 51#, 53#, 61#, 80# pins are normal. 

No 

Repair 
corresponding lines