Hummer H1 Service Manual page 46

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PROBLEM
Hard Starting 1. Wrong fuel or poor quality fuel.
When Hot
2. Air leaks in fuel supply (suction) lines.
3. Fuel return or vent line restricted.
4. Low fuel pressure to injector pump.
5. Engine shut-off solenoid problem.
6. Low compression due to rings, pistons,
valves.
Hard Starting 1. Incorrect grade of diesel fuel.
When Cold
2. Water in fuel or wax buildup in Þlter.
3. Glow plugs inoperative.
4. Fuel lift pump inoperative.
Engine Will Not 1. Shift lever not entirely in Park (or Neutral
Crank position).
2. InsufÞcient battery voltage due to:
¥ Low charge
¥ Corroded connections
¥ Damaged Cables or solenoid wires
3. Blown fuse.
4. Park/Neutral position switch problem.
05745159
Engine Diagnosis
POTENTIAL CAUSE CORRECTION
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.
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.
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 2-9