157 

No.115 Engine not running or slowly running while startup   

General malfunction part: 1. battery; 2. startup motor; 3. harness or ignition switch; 4. mechanical 
parts of the engine. General diagnosis flowchart: 

Serial No.  Operation steps 

Results   

Follow-ups   

Yes Next 

step 

1 

Check voltage between two binding posts of battery is around 8-12V 
while the engine is started with the multimeter.   

No Replace 

battery 

Yes Next 

step 

2 

With ignition switch at starting position, check binding post of anode of 
startup motor is with voltage above 8V with the multimeter. 

No 

Repair or replace 
harness 

Yes 

Repair or replace 
starting motor 

3 

Remove startup motor, and check its working conditions. Mainly check it 
is open circuited or jammed due to poor lubrication. 

No Next 

step 

Yes 

Replace for 
lubricating oil with 
proper grade 

4 

If malfunction only occurs in winter, check resistance of startup motor is 
too large due to improper selection of lubricating oil and gear case oil. 

No Next 

step 

Yes 

Check internal 
resistance of 
engine 

5 

Check internal mechanical resistance of the engine is too large, causing 
startup motor not running or slowly running. 

No Diagnosis 

help 

 

 
 

 

 

158 

No.116 While startup, engine running, but unable to start   

General malfunction part: 1. oil tank without oil; 2. fuel pump; 3. speed sensor; 4. ignition coil; 5. 
mechanical part of engine. General diagnosis flowchart: 

Serial No.  Operation steps 

Results   

Follow-ups   

Yes Next 

step 

1 

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 

2 

Connect diagnosis instrument of electric injection system and observe 
“engine speed”. Start the engine and observe speed signal is output. 

No 

Repair speed 
sensor lines 

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 

Eliminate 
mechanical failure 

4 

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

No Next 

step 

Yes Diagnosis 

help 

5 

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

 

 
 

 

 

159 

No.117 Difficult to start for hot startup   

General malfunction part: 1. fuel containing water; 2. fuel pump; 3. cooling liquid temperature 
sensor; 4. fuel pressure regulator vacuum pipe; 5. ignition coil.   
General diagnosis flowchart: 

Serial No.  Operation steps 

Results   

Follow-ups   

Yes Next 

step 

1 

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 

Repai r oil supply 
system 

Yes Next 

step 

2 

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 

Repair lines or 
replace sensor 

3 

Take out connector of cooling liquid temperature sensor, and start the 
engine. Observe the engine is successfully started at this point. (or 
connect one 300ohm resistance in series at connector of this sensor to 
replace cooling liquid temperature sensor and observe the engine is 
successfully started at this point.) 

No Next 

step 

Yes 

Repair or replace 

4 

Check fuel pressure regulator vacuum pipe is loosening or air leaking.   

No Next 

step 

Yes Replace 

fuel 

5 

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

No Next 

step 

Yes Diagnosis 

help 

6 

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

 

 
 

 

 

160 

No.118 Difficult to start for cold startup   

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. mechanical parts of engine. General 
diagnosis flowchart: 

Serial No.  Operation steps 

Results   

Follow-ups   

Yes Next 

step 

1 

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 

Repai r oil supply 
system 

Yes Next 

step 

2 

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 

Repair lines or 
replace sensor 

3 

Take out connector of cooling liquid temperature sensor, and start the 
engine. Observe the engine is successfully started at this point. (or 
connect one 300ohm resistance in series at connector of this sensor to 
replace cooling liquid temperature sensor and observe the engine is 
successfully started at this point.) 

No Next 

step 

Yes 

Clean throttle valve 
and idling speed 
duct 

4 

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

No Next 

step 

Yes 

Replace 
malfunctiony ones 

5 

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

No Next 

step 

Yes Replace 

fule 

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 engine 
cylinder is with insufficient pressure. 

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