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Hummer H1 (2002+). Manual - part 12

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Engine 2-9

05745159

Hard Starting
When Hot

Wrong fuel or poor quality fuel.

Air leaks in fuel supply (suction) lines.

Fuel return or vent line restricted.

Low fuel pressure to injector pump.

Engine shut-off solenoid problem.

Low compression due to rings, pistons,
valves.

1. Drain and reÞll tank. Purge rest of fuel system and

bleed injectors.

2. Check lines at fuel pump and injectors for leaks, or

loose Þttings. Tighten or replace lines as needed.

3. Clear or replace either line if restricted, pinched, or

damaged.

4. Replace fuel supply pump if pressure is less than

5 1/2 psi.

5. Test and replace switch or solenoid if necessary.

6. Check compression and overhaul engine if neces-

sary.

Hard Starting
When Cold

Incorrect grade of diesel fuel.

Water in fuel or wax buildup in Þlter.

Glow plugs inoperative.

Fuel lift pump inoperative.

1. Drain and reÞll fuel tank and Þlter. Bleed injectors

and purge lines as needed.

2. Drain water. Remove and clean Þlter and lines if

wax formation has occurred.

3. Check current ßow at relay. Minimum current is 55

amps. If OK, check current ßow at each glow plug.
Current should be 14 amp. Repair wiring or replace
faulty glow plug(s).

4. Check for pump operation, if inoperative check

fuses and wiring. If pump operates, check ßow.

Engine Will Not
Crank

Shift lever not entirely in Park (or Neutral
position).

InsufÞcient battery voltage due to:
¥ Low charge
¥ Corroded connections
¥ Damaged Cables or solenoid wires

Blown fuse.

4. Park/Neutral position switch problem.

1. Check and correct linkage adjustment as needed.

2. Check batteries and cable connections. Charge low

batteries and check generator and belt. Replace
failed battery(s). Clean corrosion from cables con-
nections. Replace or repair cables or terminals as
needed.

3. Check fuse condition at fuse boxes. If blown fuse

is found, check circuit for shorts, grounds.

4. Test switch continuity with ohmmeter. Replace

switch if open/shorted.

Engine Diagnosis

PROBLEM

POTENTIAL CAUSE

CORRECTION

2-10

Engine

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Engine Will Not
Crank -
(Continued)

Starter or solenoid problem.

Hydrostatic lock. Combustion chambers
Þlled with fuel, or coolant due to faulty injec-
tors, or blown head gasket. (Remove glow
plugs, crank engine and note ßuid coming
out of plug holes).

Flywheel ring gear teeth or starter Bendix
damaged.

5. Check for bad or loose connections at starter and

solenoid. If OK, note if starter surges when current
is applied. Problem may be with Bendix or arma-
ture.

6. Test and replace injectors that are stuck open.

Replace blown head gasket or replace head if
cracked.

7. Remove transmission access cover and inspect ring

gear and bendix. Replace ßywheel or starter Ben-
dix as necessary.

Engine Stalling

Air leaks in fuel lines.

Fuel Þlter partially plugged by wax forma-
tion, dirt/sludge, or partially water Þlled.

Misfueled, wrong fuel, or low quality fuel.

Restricted air intake due to plugged Þlter ele-
ment, air cleaner, intake duct. Generally
caused by extended off -road operation in
dusty areas.

Fuel supply pump problem or restriction in
fuel lines, injector pump, or injectors.

Fuel drain back or return lines restricted/
damaged.

1. Check lines from fuel pump to injectors. Replace

lines that leak or have damaged Þttings. Tighten
loose injectors. Bleed injectors afterward.

2. Drain off Þlter contents at draincock. Clean out

fuel tank and lines if Þlter contained sludge. Clean
out Þlter if full of wax or dirt.

3. Drain and reÞll tank. Drain fuel Þlter and bleed

injectors.

4. Replace Þlter if necessary. Remove and clean out

air cleaner body, intake duct, cap, hoses, and dust
unloader.

5. Check fuel ßow at pump and injectors. Supply

pump minimum pressure is 5 1/2 psi. Replace
worn, damaged, or failed parts.

6. Inspect and repair or replace lines, clamps as

needed.

Engine Diagnosis

PROBLEM

POTENTIAL CAUSE

CORRECTION

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Engine 2-11

05745159

Low Power,
Poor Accelera-
tion

Vehicle overloaded.

Low grade diesel fuel.

Sludge or wax buildup in fuel Þlter (low fuel
supply).

Air in fuel supply system.

Fuel supply pump failed.

Mistimed injection pump.

Restriction in air intake system.

Vacuum pump failure.

Engine shut-off solenoid has intermittent
open or short.

10. Turbocharger, related wiring, or wastegate

actuator fault may have occurred. May also
be caused by exhaust gasket failure.

11. Injection pump, or injector failure.

12. Engine problem:

¥ Timing chain and gears worn.
¥ Cam and injection pump gears mistimed.
¥ Piston, ring, or valve wear.
¥ Worn cam lobes.
¥ Damaged piston(s).

1. Lighten vehicle load.

2. Drain tank and refuel.

3. Drain and clean Þlter.

4. Check lines from fuel supply pump and to injec-

tors. Replace leaking, damaged lines as needed.
Bleed air at injector fuel line Þttings.

5. Check and replace pump if output is less than 5 1/2

psi.

6. Check and correct as needed.

7. Check air intake cap, duct, air cleaner, hoses, and

air horn. Clean/repair as needed. Replace Þlter if
plugged.

8. Replace pump if inoperative.

9. Check wiring and solenoid. Repair wiring and con-

nectors. Replace solenoid if failed.

10. Check wiring, wastegate vacuum actuator, and

PCM with Tech I scan tool. Run vacuum check on
actuator and vacuum pump with vacuum tool.
Check for intake/exhaust leaks. Replace turbo-
charger, or related components as indicated by
diagnosis.

11. Diagnose and replace pump as needed. Replace

damaged injectors.

12. Check compression and timing. Then disassemble

engine and repair as needed. Remove engine com-
pletely if diagnosis indicates crankshaft, rod, or
piston problem.

Exhaust Smoke:
Blue Smoke

CDR valve faulty.

Worn piston rings, valve stem seals, or valve
guides.

1. Check valve operation with manometer or vacuum

hand pump. Clean or replace valve and hose if nec-
essary.

2. Remove glow plugs and check compression. Then

repair valve train and cylinder heads, or perform
piston ring replacement.

Engine Diagnosis

PROBLEM

POTENTIAL CAUSE

CORRECTION

2-12

Engine

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White Smoke

Low quality fuel.

Injection pump/engine timing is retarded.

Engine coolant entering combustion chamber
through blown gasket, cracked head, loose/
damaged head bolts. May be accompanied
by low coolant level and overheating.

Low ambient temperatures (below freezing).

1. Drain and reÞll tank with better quality fuel.

2. Check and correct timing.

3. Verify problem and repair as necessary. Replace

cracked head, block, or head gasket.

4. Normal condition caused primarily by water vapor.

Not a concern unless it continues after warmup.

Black Smoke

Low grade diesel fuel.

Overrich fuel mixture:
¥ Drain/return lines restricted.
¥ Injector(s) stuck open.
¥ Engine speed or throttle sensor fault.

Black smoke at wide open throttle.

1. Drain and reÞll tank.

2. Test, diagnose and repair as required.

3. Restriction in air intake system, no vacuum to

wastegate actuator, damaged wastegate, or air leak
at intake or exhaust manifold.

Gray Smoke

Long idle periods.

Low grade fuel.

Fuel tank vent restricted.

Fuel return line restricted.

Engine problem (low compression excessive
blowby, worn rings or valve stem seals).

1. Try to avoid prolonged idling.

2. Add proper quality fuel. (not necessary to drain and

reÞll tank).

3. Clear vent and line.

4. Clear restriction. Replace line if kinked or pinched.

5. Diagnose and repair as indicated.

Engine Diagnosis

PROBLEM

POTENTIAL CAUSE

CORRECTION

Content .. 10 11 12 13 ..