Housing Pressure Cold Advance (HPCA)

This feature is used on all 1981 and 1983---84 engines and advances the injection timing 3° during cold operation. This circuit is actuated by a temperature switch calibrated to open the circuit at 125°F. Below the switching point, housing pressure is decreased from 10 to 0 psi which advances the injection timing 3°. Above the switching point, the switch opens, de-energizing the solenoid and the housing pressure is returned to 10 psi. The fast idle solenoid is energized by the same switch and closes when the temperature falls below 95°F.