Evaporative Emissions System: Testing and Inspection

Chart C-3:

Chart C-3 Wiring Diagram:

CIRCUIT DESCRIPTION:

The canister purge is controlled by a solenoid that allows vacuum to purge the fuel vapor canister when energized. The ECM supplies a ground to power the solenoid (purge "ON"). If the diagnostic test terminal is grounded with the engine not running, or the following conditions exists with the engine running, the purge solenoid is energized (purge "ON").

^ The engine run time after start is more than 45 seconds cold and/or 20 seconds when engine coolant temperature is above 85~C (185~F).
^ The coolant temperature is above 70~C (158~F).


TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. Checks to see if the solenoid is being commanded open or closed by the ECM. The solenoid is normally de-energized in this step, so it should be closed.

2. Completes functional check. This should normally energize the solenoid and allow the vacuum to drop (Purge "ON").


DIAGNOSTIC AIDS:

^ Inspect the canister for cracks or fuel saturation.

^ Inspect fuel vapor lines from the fuel tank for leaks, being disconnected or sharp bends blocking the flow of vapors.