Evaporative Emissions System: Testing and Inspection
INCORRECT OPERATION MAY CAUSE:
1. Poor idle, stalling, and poor driveability. Check for:
a. Inoperative purge solenoid.
b. Damaged vapor canister.
c. Hoses split, cracked, or not connected to the proper tubes.
d. Pinched or plugged hose(s).
2. Evidence of fuel loss or fuel vapor odor. Check for:
a. Liquid fuel leaking from fuel lines, or TBI unit.
b. Cracked or damaged fuel vapor canister.
c. Disconnected, misrouted, kinked, deteriorated, damaged vapor hoses, or control hoses.
Wiring Diagram for Canister Purge Valve:
CANISTER PURGE VALVE CHECK
CIRCUIT DESCRIPTION:
The canister purge is controlled by a solenoid that allows ported vacuum to purge the canister when energized. The ECM controls the ground to activate the solenoid. If the following conditions exist, while the engine is running, the canister purge solenoid is energized (purge ON).
1. The engine run time is more than one minute.
2. The vehicle speed is above 5 mph.
3. The throttle is off-idle.
Chart C-3:
TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.
1. This checks to see if the solenoid is opened or closed. The canister purge circuit should be open and the solenoid should be closed (de-energized).
2. With the engine OFF, and the ignition in the ON position, the canister purge circuit should be closed. This activates the circuit and should open the solenoid.
3. This checks for a complete circuit. Normally there is ignition voltage on circuit 439, and the ECM provides the ground path on circuit 428. A short in the canister purge solenoid could cause an open circuit in the ECM.
NOTE: Once the test sequence is completed or after repairs, clear the codes and verify NO "SERVICE ENGINE SOON" light exist.
DIAGNOSTIC AIDS:
This describes the normal operation of the canister purge solenoid.
With the ignition "ON," engine not running, the canister purge solenoid will be energized. With the engine running at base idle speed, the canister purge solenoid will not be energized.