G 20 Van V8-379 6.2L DSL VIN C FI (1992)
Cold Advance: Description and Operation
Cold Advance System Circuit
Purpose:
The cold advance control circuit is designed to advance the injection timing about 4° during cold operation. The ECM controls a cold advance
relay which in turn controls the cold advance solenoid.
Operation:
The ECM opens the circuit above coolant temperature of 95°F (35°C). Below the switching point with the key "ON", the cold advance solenoid is
continuously energized without the engine running. Below the switching point and the engine running, the ECM closes the circuit to the cold
advance solenoid.
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 relay is mounted on the right side of the firewall.
The cold advance solenoid is mounted under the injection pump cover.
