Hummer H1 Service Manual page 48

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PROBLEM
Low Power, 1. Vehicle overloaded.
Poor Accelera-
tion 2. Low grade diesel fuel.
3. Sludge or wax buildup in fuel Þlter (low fuel
supply).
4. Air in fuel supply system.
5. Fuel supply pump failed.
6. Mistimed injection pump.
7. Restriction in air intake system.
8. Vacuum pump failure.
9. 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).
Exhaust Smoke: 1. CDR valve faulty.
Blue Smoke
2. Worn piston rings, valve stem seals, or valve
guides.
05745159
Engine Diagnosis
POTENTIAL CAUSE CORRECTION
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.
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 2-11