K 1500 Truck 4WD V8-379 6.2L DSL VIN J FI (1992)
Cold Advance: Description and Operation
Cold Advance And Shutdown Solenoids
Purpose:
The housing pressure cold advance feature advances the injection timing about four degrees during cold operation. This provides better cold starts,
improved cold idle, and emission control.
Operation:
The circuit is actuated by a coolant temperature switch on the rear of the right cylinder head. The switch is calibrated to open the circuit at 35°C
(95°F). Below the switching point, timing is advanced by decreasing housing pressure from 68.95 kPa (10 psi) to zero. Above the switching point,
the housing pressure is returned to 68.95 kPa (10 psi). The fast idle solenoid is energized by the same switch.
When the solenoid is activated, it will push a pin in the return line valve (located on the top of the injector pump cover), changing the return line
pressure, which in turn changes the injector pump housing pressure. The return line valve may be removed and checked to see if it is sticking
manually. The return line valve also incorporates a filter screen internally which should be checked. Excessive particles in the screen may indicate
some type of internal injector pump damage.
When the cold advance solenoid is energized and the engine is running, the housing pressure is decreased from 69 kPa (10 psi) to zero, which
advances the timing 4°. After the engine begins to warm up, the cold advance solenoid is de-energized and the housing pressure is returned to 69
kPa (10 psi).
Location:
The cold advance solenoid is mounted under the injection pump cover.
