Evaporative Emissions System: Testing and Inspection

Functional Check:

Fuel Tank Pressure Control Valve:

Fuel Tank Pressure Control Valve
With hand vacuum pump, apply approximately 38 cm Hg (15" Hg) to the control vacuum tube. After ten seconds, there should be at least 13 cm Hg (5" Hg) vacuum remaining. If after 10 seconds there is less than specified vacuum, replace the valve.

With 38 cm Hg (15" Hg) applied to control vacuum tube, attach a short piece of hose to the valves tank tube side. Blow into the tube. You should feel air pass through the valve. If not, replace the valve.

Inspect
Ensure all connections and vacuum lines are tight and free of cracks, damage and restrictions. Visually check vapor canister for cracks and/or damage.

Canister Purge Test:

Purge Solenoid Circuit Diagram:

Circuit Description
Canister purge is controlled by a solenoid that allows manifold vacuum to purge the fuel vapor canister when energized. The PCM supplies a ground to energize the solenoid. If the diagnostic "test" terminal is grounded with the engine stopped and ignition "ON", or the following conditions are met with the engine running, the purge solenoid will be energized (purge "ON").

^ Engine run time after start more than 1 minute
^ Coolant temperature above 60°C (140°F)
^ Vehicle speed above 2 mph
^ Throttle off idle, above 3%
^ IAT is less than 105°C (221°F)

Test Description

1. Disconnect vacuum hose to throttle body at purge solenoid and connect hand operated vacuum pump with gauge, to the solenoid valve.
2. Apply approx. 38 cm Hg (15" Hg) vacuum. Vacuum should hold. If not, replace purge solenoid valve.
3. Disconnect solenoid electrical harness connector and apply battery power and ground to the solenoid terminals. Solenoid should energize and vacuum gauge reading should drop to zero. If so, solenoid valve is OK. If not, replace solenoid valve.

Diagnostic Aids
Normal operation of the canister purge solenoid described as follows:
^ With the ignition "ON", engine "OFF", output/field service enable terminal of the [1][2]DLC grounded, the canister purge solenoid should become energized.

^ If circuit 339 (power supply) is open or shorted to ground, the solenoid will not energize and vapor canister will not purge.

^ If circuit 428 (driver circuit) is open, or shorted to power, the purge solenoid will not energize and vapor canister will not purge.

^ If circuit 428 (driver circuit) is shorted to ground, the solenoid will be energized whenever the ignition is turned "ON" and the canister will be purging whenever the engine is running. This may cause rough idle.