Hummer H1 Service Manual page 151

3-14 Fuel, Emissions, and Exhaust
Installation
3. Install the O-ring seal above the threads at the bottom of
the new solenoid (Figure 3-14).
4. Install the replacement solenoid into the injector pump
housing and torque to 19 lb-ft (25 N•m).
5. Connect the electrical connector to the ESO solenoid.
6. Start the engine and check for leaks.
O-RING
Figure 3-14: Two Styles Of Solenoids
Optical/Fuel Temperature Sensor Tests
The optical/fuel temperature sensor supplies three signals to
the PCM for fuel control and timing. A high resolution signal
helps determine injection timing and fuel control. A pump cam
signal provides reference pulses that monitor and help deter-
mine injection timing. The fuel temperature signal helps the
WIRE
HARNESS
Figure 3-15: Optical/Fuel Temperature Sensor Circuit
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PCM determine pump advance or retard requirements and fuel
flow. The sensor is located at the top of the injection pump ad-
jacent to the fuel shut-off solenoid.
A fault in the optical sensor or related wiring will produce fast
idle and performance problems. A problem will cause a high
resolution circuit fault, or a cam reference pulse error fault.
The sensor can be checked with a scan tool and a voltmeter as
follows:
High Resolution Fault Test
1. Turn ignition off.
2. Disconnect sensor harness connector.
3. Turn ignition on.
4. Connect voltmeter to sensor terminal A, of the harness,
and to ground (Figure ).
• If meter indicates 5 volts, continue with test.
• If meter indicates zero voltage, look for open/short in
wire to PCM 5 volt reference terminal, connector, or
PCM.
5. Connect volt/ohmmeter to a good engine ground and to
sensor ground terminal D:
• If resistance is .2 W or less, proceed to next test step.
• If resistance is greater than .2 W , problem is with ground
wire, connector, or sensor.
Fuel Solenoid and Solenoid Driver
The solenoid and driver provide the fuel injection metering to
the individual injectors. The driver receives the PCM com-
mand and transmits it to the solenoid which controls the actual
injection process.
The solenoid driver also returns a pulse width signal back to
the PCM. This signal informs the PCM that injection has taken
place. The pulse width signal time is in milliseconds.
A fault in either component will cause an injection pulse width
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