Hummer H2. Manual - part 27

DIESEL ENGINE TROUBLE SHOOTING 

BASIC DIESEL ENGINE TROUBLE SHOOTING CHART 

Frozen or binding heated air inlet 

Inspect heated air door for binding 

Hesitation With Heavy Gas Pedal Movement 

Defective accelerator pump 

Replace pump, see FUEL SYSTEMS 

Metering rod carrier sticking or 
binding 

Remove restriction 

Large vacuum leak 

Inspect vacuum system and repair leak 

Float level setting too low 

Reset float level, see FUEL SYSTEMS 

Defective fuel pump, lines or filter 

Inspect pump, lines and filter 

Air door setting incorrect 

Adjust air door setting, see FUEL 

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. 

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 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Trouble Shooting - Basic Procedures

  

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 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Trouble Shooting - Basic Procedures

  

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 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Trouble Shooting - Basic Procedures

  

VACUUM PUMP DIAGNOSIS 

FUEL INJECTION TROUBLE SHOOTING 

BASIC FUEL INJECTION TROUBLE SHOOTING CHART 

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 

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 

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. 

CONDITION & POSSIBLE 
CAUSE 

CORRECTION 

Engine Won't Start (Cranks Normally) 

Cold start valve inoperative 

Test valve and circuit 

Poor connection;vacuum or 
wiring 

Check vacuum and electrical connections 

Contaminated fuel 

Test fuel for water or alcohol 

Defective fuel pump relay or 
circuit 

Test relay and wiring 

Battery too low 

Charge and test battery 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Trouble Shooting - Basic Procedures