DIESEL ENGINE TROUBLESHOOTING
| NOTE: | This is GENERAL information. This article is not intended to be specific to any unique situation or individual vehicle configuration. The purpose of this Troubleshooting information is to provide a list of common causes to problem symptoms. For model-specific Troubleshooting, refer to SUBJECT, DIAGNOSTIC, or TESTING articles available in the section(s) you are accessing. |
| NOTE: | Diesel engines mechanical diagnosis is the same as gasoline engines for items such as noisy valves, bearings, pistons, etc. The following trouble shooting covers only items pertaining to diesel engines. |
BASIC DIESEL ENGINE TROUBLESHOOTING CHART
| CONDITION & POSSIBLE CAUSE | CORRECTION | |
|---|---|---|
| Engine Won't Crank | ||
| Bad battery connections or dead batteries | Check connections and/or replace batteries | |
| Bad starter connections or bad starter | Check connections and/or replace starter | |
| Engine Cranks Slowly, Won't Start | ||
| Bad battery connections or dead batteries | Check connections and/or replace batteries | |
| Engine oil too heavy | Replace engine oil | |
| Engine Cranks Normally, But Will Not Start | ||
| Glow plugs not functioning | Check glow plug system, see FUEL SYSTEMS | |
| Glow plug control not functioning | Check controller, see FUEL SYSTEMS | |
| Fuel not injected into cylinders | Check fuel injectors, see FUEL SYSTEMS | |
| No fuel to injection pump | Check fuel delivery system | |
| Fuel filter blocked | Replace fuel filter | |
| Fuel tank filter blocked | Replace fuel tank filter | |
| Fuel pump not operating | Check pump operation and/or replace pump | |
| Fuel return system blocked | Inspect system and remove restriction | |
| No voltage to fuel solenoid | Check solenoid and connections | |
| Incorrect or contaminated fuel | Replace fuel | |
| Incorrect injection pump timing | Re-adjust pump timing, see FUEL SYSTEMS | |
| Low compression | Check valves, pistons, rings, see ENGINES | |
| Injection pump malfunction | Inspect and/or replace injection pump | |
| Engine Starts, Won't Idle | ||
| Incorrect slow idle adjustment | Reset idle adjustment, see TUNE-UP | |
| Fast idle solenoid malfunctioning | Check solenoid and connections | |
| Fuel return system blocked | Check system and remove restrictions | |
| Glow plugs go off too soon | See glow plug diagnosis in FUEL SYSTEMS | |
| Injection pump timing incorrect | Reset pump timing, see FUEL SYSTEMS | |
| No fuel to injection pump | Check fuel delivery system | |
| Incorrect or contaminated fuel | Replace fuel | |
| Low compression | Check valves, piston, rings, see ENGINES | |
| Injection pump malfunction | Replace injection pump, see FUEL SYSTEMS | |
| Fuel solenoid closes in RUN position | Check solenoid and connections | |
| Engines Starts/Idles Rough W/out Smoke or Noise | ||
| Incorrect slow idle adjustment | Reset slow idle, see TUNE-UP | |
| Injection line fuel leaks | Check lines and connections | |
| Fuel return system blocked | Check lines and connections | |
| Air in fuel system | Bleed air from system | |
| Incorrect or contaminated fuel | Replace fuel | |
| Injector nozzle malfunction | Check nozzles, see FUEL SYSTEMS | |
| Engines Starts and Idles Rough W/out Smoke or Noise, But Clears After Warm-Up | ||
| Injection pump timing incorrect | Reset pump timing, see FUEL SYSTEMS | |
| Engine not fully broken in | Put more miles on engine | |
| Air in system | Bleed air from system | |
| Injector nozzle malfunction | Check nozzles, see FUEL SYSTEMS | |
| Engine Idles Correctly, Misfires Above Idle | ||
| Blocked fuel filter | Replace fuel filter | |
| Injection pump timing incorrect | Reset pump timing, see FUEL SYSTEMS | |
| Incorrect or contaminated fuel | Replace fuel | |
| Engine Won't Return To Idle | ||
| Fast idle adjustment incorrect | Reset fast idle, see TUNE-UP | |
| Internal injection pump malfunction | Replace injection pump, see FUEL SYSTEMS | |
| External linkage binding | Check linkage and remove binding | |
| Fuel Leaks On Ground | ||
| Loose or broken fuel line | Check lines and connections | |
| Internal injection pump seal leak | Replace injection pump, see FUEL SYSTEMS | |
| Cylinder Knocking Noise | ||
| Injector nozzles sticking open | Test injectors, see FUEL SYSTEMS | |
| Very low nozzle opening pressure | Test injectors and/or replace | |
| Loss of Engine Power | ||
| Restricted air intake | Remove restriction | |
| EGR valve malfunction | Replace EGR valve | |
| Blocked or damaged exhaust system | Remove restriction and/or replace components | |
| Blocked fuel tank filter | Replace filter | |
| Restricted fuel filter | Remove restriction and/or replace filter | |
| Block vent in gas cap | Remove restriction and/or replace cap | |
| Tank-to-injection pump fuel supply blocked | Check fuel lines and connections | |
| Blocked fuel return system | Remove restriction | |
| Incorrect or contaminated fuel | Replace fuel | |
| Blocked injector nozzles | Check nozzle for blockage, see FUEL SYSTEMS | |
| Low compression | Check valves, rings, pistons, see ENGINES | |
| Loud Engine Noise With Black Smoke | ||
| Basic timing incorrect | Reset timing, see FUEL SYSTEMS | |
| EGR valve malfunction | Replace EGR valve | |
| Internal injection pump malfunction | Replace injection pump, see FUEL SYSTEMS | |
| Incorrect injector pump housing pressure | Check pressure, see FUEL SYSTEMS | |
| Engine Overheating | ||
| Cooling system leaks | Check cooling system and repair leaks | |
| Belt slipping or damaged | Check tension and/or replace belt | |
| Thermostat stuck closed | Remove and replace thermostat, see ENGINE COOLING | |
| Head gasket leaking | Replace head gasket | |
| Oil Light on at Idle | ||
| Low oil pump pressure | Check oil pump operation, see ENGINES | |
| Oil cooler or line restricted | Remove restriction and/or replace cooler | |
| Engine Won't Shut Off | ||
| Injector pump fuel solenoid does not return fuel valve to OFF position | Remove and check solenoid and replace if needed | |
VACUUM PUMP DIAGNOSIS
| CONDITION & POSSIBLE CAUSE | CORRECTION | |
|---|---|---|
| Excessive Noise | ||
| Loose pump-to-drive assembly screws | Tighten screws | |
| Loose tube on pump assembly | Tighten tube | |
| Valves not functioning properly | Replace valves | |
| Oil Leakage | ||
| Loose end plug | Tighten end plug | |
| Bad seal crimp | Remove and re-crimp seal | |
