8. Fuel system
126
Failure Diagnosis
Symptom Causes Troubleshooting
1. Engine does not start
A. Fuel is not supplied from the
fuel delivery pump
B. Fuel is not injected from the
fuel injection pump
C. Improper fuel injection timing
D. Fuel injection nozzle not
working
• Clogged fuel pipe, or air entered the fuel pipe line
• Defective delivery pump valve
• Seized delivery pump piston or push rod
• Correct
• Replace
• Disassemble / correct
• Clogged fuel filter cartridge
• Air entered to the fuel filter or injection pump
• Seizure or defect in the plunger or delivery valve
• Clean / replace
• Bleed
• Disassemble / correct
• Defective installation of fuel injection pump bracket
• Defective adjustment of the fuel injection pump tappet
• Excessively worn cam of camshaft
• Inspect / correct
• Inspect / correct
• Replace
• Seizure of needle valve of nozzle
• Fuel leakage between nozzle and needle valve
• Improper fuel injection pressure
• Service or replace
• Service or replace
•Adjust
2. Engine starts but stops imme-
diately
• Clogged fuel filter or clogged pipe between fuel
delivery pump and injection pump
• Air entered into fuel
• Insufficient supply of oil by fuel delivery pump
• Clogged air breather in fuel tank, causing insufficient
fuel supply.
• Clean or replace
• Air bleeding
• Disassemble / correct
• Replace breather
3. Insufficient engine power
• Excessively work plunger
• Improper injection timing
• Defective delivery valve
• Excessive fuel leakage in injection nozzle
• Nozzle not working properly
• Replace
•Adjust
• Replace
• Service or replace
• Disassemble / correct
4. Engine knocking occurs
• Early injection timing
• High nozzle injection pressure
• Nozzle not working properly
•Adjust
•Adjust
• Disassemble / correct
5. Excessive engine smoke and
knocking
• Defective injection timing
• Too low nozzle injection pressure
• Broken nozzle spring
• Nozzle not working properly
• Excessively work plunger
• Defective delivery valve seat
• Excessive fuel supply
•Adjust
•Adjust
• Replace it
• Replace it
•Adjust
• Replace it
• Check feed pump
6. Unstable engine power
• Insufficient fuel supply
• Air entered into fuel
• Water entered into fuel
• Defective plunger operation
• Defective actuator operation
• Defective nozzle
• Injection start pressure different between cylinders
• Defective controller
• Check feed pump
• Air bleeding
• Replace fuel
• Disassemble / correct
• Disassemble / correct
• Disassemble / correct
•Adjust
•Adjust
7. Engine cannot reach the max.
speed
• Nozzle not working properly
• Defective operation of actuator or controller
• Disassemble / correct
•Adjust
8. Unstable engine idling
• Defective controller operation
• Defective plunger operation
• Defective magnetic pickup sensor
•Adjust
• Disassemble / correct
• Inspect or replace
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