Hummer H1 Service Manual page 145

3-8 Fuel, Emissions, and Exhaust
PROBLEM
No Start Condi- 1. Excessive amount of water or wax buildup in
tion (engine system.
cranks but will
not run)
2. Blown fuse.
3. No fuel to injection pump.
4. No fuel to injectors.
5. Engine fault:
• broken camshaft
• damaged injection pump gears
• timing chain or gear failure
6. Fuel tank select valve problem.
7. No inject signal from PCM.
8. Injection pump failure.
9. PCM ground or feed circuit fault (on ground
or ignition voltage reference signal).
10. PCM fault.
Engine Starts 1. Air leak in fuel feed line.
then Stalls
2. Glow plug fault (cold ambient temperature).
3. Restriction in fuel tank vent or return lines.
4. Fuel-lift pump pressure below 2 psi (14 kPa)
at injection pump, or 5.8 psi (40 kPa) at fuel
pump outlet.
5. Idle rpm too low.
6. No injection signal to PCM (turbo diesel).
_____________________________________________
Fuel System Diagnosis—Diesel Engine
POTENTIAL CAUSE CORRECTION
1. Draw off sample at drain plug. Drain and flush sys-
tem if necessary.
2. Replace fuse. Check for shorts-grounds in affected
circuit.
3. Test fuel-lift pump output. Replace pump if pres-
sure is below 5.8 psi (40 kPa). Check lines and
filter for restrictions if pump output is OK. Also
test pump relay. Be sure pump relay is being
energized when ignition switch is in crank or start
position. Check fuel level in tanks
4. Check shut off solenoid. Check fuel solenoid
driver feed (terminal A) and ground (terminal C)
circuits.
5. Inspect and repair as needed.
6. Replace valve if it won't switch from main to aux-
iliary and back. NOTE: the valve will only operate
if the fuel lift pump is energized!
7. Run scan tool test and replace failed sensor,
harness wire, or connector.
8. Replace pump but only if failure is indicated by
scan tool and pressure test.
9. Confirm with scan tool. Use multimeter to locate
fault.
10. Confirm with scan tool before replacement.
1. Inspect lines and repair as needed. Bleed injectors
afterward.
2. Test and repair wiring, or replace failed glow plugs
or relay/controller.
3. Inspect and clear restriction. Replace cap vent, or
lines as needed.
4. Replace pump but only if fuel lines to pump are not
blocked, plugged, or restricted. Also be sure flow
through 2-stage filter is not restricted as well.
5. Adjust idle to required rpm.
6. Test with scan tool and replace failed sensor or
harness.
®