Hummer H1 Service Manual page 148

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SCAN TOOL DIAGNOSIS
The scan tool is needed for operational testing of electronic
components such as the PCM, electronic accelerator pedal po-
tentiometer, and engine sensors.
The scan tool is connected to the vehicle electrical system
through the diagnostic/data link connector. The connector is a
black 16-way connector. It is located under the instrument
panel near the steering column.
Refer to Section 2 for detailed information on scan tool use.
Fuel Pump Pressure Test
Fuel pump pressure should be 5.8-8.7 psi (40-60 kPa) at idle.
1. Disconnect fuel line at fuel filter inlet port.
2. Install a tee adapter in fuel line between pump and filter
inlet port.
3. Connect test gauge to tee adapter. Gauge should have
pressure capacity up to 20 psi (138 kPa).
4. Start and run engine and record fuel pump pressure.
5. If pump pressure is less than 5.8 psi (40 kPa), replace
pump and retest pressure.
6. Remove pressure gauge and tee adapter. Reconnect fuel
line to filter inlet.
Diesel Fuel Injector Test
WARNING: Nozzle tester tool J–29075-AMG dupli-
cates normal injector operating pressures which can
exceed 1700 psi (117 bar). Never place hands or arms
near the injector nozzle during the test. The high pres-
sure, finely atomized spray from the nozzle can pene-
trate flesh, destroy tissue, and result in blood poisoning.
It is recommended that a clear protective receptacle be
positioned around the injector to contain the spray. A
receptacle can be fabricated from 3/16 to 1/4 in. clear
plastic for test purposes.
The test requires a nozzle tester tool J–29075-AMG, injector
adapter kit J–29079-125, a length of clear plastic 1/8 or 3/16
I.D. tubing, and a drip pan.
1. Locate faulty injector by loosening fuel line fitting
momentarily at each injector. Faulty injector will not have
much affect on engine operation.
2. Remove suspect injector(s) from engine.
3. Install clear plastic tube on fuel drain/return ports on
injector.
4. Attach injector to fitting and line on test tool (Figure 3-10).
5. Close shutoff valve on tool (Figure 3-10).
5745159
Fuel, Emissions, and Exhaust
INJECTOR
FITTING
AND LINE
NOZZLE
PRESSURE
GAUGE
NOZZLE TESTER
J–29075-AMG
Figure 3-10: Pressure Testing Diesel Fuel Injector
6. Position drip pan under injector.
7. Place protective receptacle or box around injector.
8. Pump test tool handle to fill line, fitting, and injector with
test fluid.
9. Test injector nozzle opening pressure as follows:
a. Open test tool shutoff valve 1/4 turn.
b. Press tool pump handle slowly downward and note
pressure where test gauge needle stops.
c. Maximum observed pressure represents injector
opening pressure. Compare values to Fuel Injection
Nozzle table on page 3–12.
d. Replace injector if opening pressure is less than speci-
fied.
e. Replace injector if it does not have a uniform conical
spray pattern.
10. Test injector nozzle leakage as follows:
a. Open test tool shutoff valve an additional 1/2 to 1 1/2
turns.
b. Press tool pump handle slowly downward until test
tool gauge is at 1400 psi (95 bar) and observe injector
nozzle tip.
3-11
PART OF
J–29079-125
ADAPTER KIT
SHUTOFF
VALVE
KNOB
PUMP
HANDLE