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