Diesel Engine Trouble Shooting
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 Trouble Shooting information is to provide a list of common causes to problem symptoms. For model-specific Trouble Shooting, 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 TROUBLE SHOOTING 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 | |