HYOSUNG 2010 ST7 Service Manual page 261

9-5 SERVICING INFORMATION
ENGINE
Complaint
Engine will not
start or is hard
to start.
Symptom and possible causes
Compression too low
1. Tappet clearance out of adjustment.
2. Worn valve guides or poor seating of valves.
3. Mistimed valves.
4. Excessively worn piston rings.
5. Worn-down cylinder bore.
6. Starter motor cranks too slowly.
7. Poor seating of spark plugs.
Plug not sparking
1. Fouled spark plugs.
2. Wet spark plugs.
3. Defective ignition coils.
4. Open or short in high-tension cord.
5. Defective pick-up coil.
6. Defective ECU.
7. Open-circuited wiring connections.
No fuel reaching the intake manifold
1. Clogged fuel filter or fuel hose.
2. Defective fuel pump.
3. Defective fuel pressure regulator.
4. Defective fuel injector.
5. Defective fuel pump relay.
6. Defective ECU.
7. Open-circuited wiring connections.
Incorrect fuel/air mixture
1. TP sensor out of adjustment.
2. Defective fuel pump.
3. Defective fuel pressure regulator.
4. Defective TP sensor.
5. Defective pick-up coil.
6. Defective IAP sensor.
7. Defective ECU.
8. Defective WT sensor.
9. Defective IAT sensor.
Remedy
Adjust.
Repair or replace.
Adjust.
Replace.
Replace.
See electrical section.
Retighten.
Clean.
Clean and dry.
Replace.
Replace.
Replace.
Replace.
Repair or replace.
Clean or replace.
Replace.
Replace.
Replace.
Replace.
Replace.
Check and repair.
Adjust.
Replace.
Replace.
Replace.
Replace.
Replace.
Replace.
Replace.
Replace.