Chart C-6 HPCA Electrical Check: VIN N (5.7L) VIN T (4.3L)

Fig. 066 - WIRING DIAGRAM for Chart C-6 HPCA Electrical Check. VIN N, VIN T:

CHART C-6

HPCA ELECTRICAL CHECK

4.3L VIN "T"

5.7L VIN "N"

The Housing Pressure Cold Advance (HPCA) solenoid operates in conjunction with the fuel injection pump return fuel line connector/pressure regulator. During normal operation the HPCA will be energized by the ECM at engine coolant temperatures of 37°C (66.6°F) and below and/or at altitudes above approximately 4,000 ft. When the HPCA solenoid is energized, the HPCA solenoid plunger extends and pushes the pressure regulator check ball off its seat. Housing pressure then drops which results in advanced fuel injection pump timing. At altitudes above approximately 4,000 ft. (1,219 M) housing pressure and injection pump timing are affected also by the operation of the ECM controlled Housing Pressure Altitude Advance (HPAA). Advanced injection pump timing is desired on a cold engine to reduce emissions, white smoke and noise as well as improving cold starting and idle quality.
This chart is to be used for HPCA electrical diagnosis only.

Fig. 065 - Chart C-6 HPCA Electrical Check.:

1. Checks for available ignition voltage through the HPCA solenoid and checks for ground on circuit from ECM terminal "B" to HPCA solenoid. Light should be "ON".
2. By disconnecting the MAP sensor altitude is simulated and the ECM should energize the HPCA solenoid. (Light off).
3. Determines if problem is due to faulty ECM or open circuit.
4. Checks for available ignition voltage at HPCA solenoid, identifying source of problem as ignition feed, grounded circuit from ECM or open solenoid.