System Operation

Purge Control System Diagram (Turbo):

The vapors generated in the fuel tank while driving or when the engine is at a stop enters the charcoal canister where the charcoal absorbs and stores the fuel vapor.
The purge solenoid is spring loaded open and closes when grounded by the ECU. While the purge solenoid is open (ungrounded), manifold vacuum is bled to a port at the air-intake. When the ECU grounds the purge solenoid, manifold vacuum is redirected to the lower vacuum chamber of the dual control purge valve. Vacuum pulls the valve open and the canister is purged by the depression within the air cleaner. Air cleaner depression is a form of vacuum, but much less than manifold vacuum. It is used on the turbo purge systems to allow the canister to be purged under a vacuum or a boost condition. The valve can be "pulled" open by a vacuum or "pushed" open by boost pressure.
When the turbocharger is in operation, the bleed port at the air-intake becomes a boost feed nipple. If the purge solenoid is grounded (closed), boost pressure is directed to the pressure chamber of the dual control purge valve. This may cause the purge valve to open, allowing the canister to be purged.
When the purge solenoid is open (ungrounded), the ports of the purge solenoid are connected, causing equal boost pressures to be applied to both nipples of the dual control purge valve. This causes the spring to push the diaphragm and the valve closed, shutting off the canister purge. The same thing happens at wide open throttle or heavy loads.
The ECU will ground the purge control solenoid after the coolant sensor indicates higher than 158~F and the air flow sensor indicates an intake air flow rate equivalent to 3,000 rpm.



The canister is purged (solenoid energized) under the following conditions:
CONDITION 1
Engine temperature above 158° F (70° C).
For the first three minutes after starting engine.
Engine rpm over 3000

CONDITION 2
Engine temperature above 158° F (70° C).
After three minutes of engine operation, the canister will be purged intermittently.
Engine rpm over 3000

CONDITION 3
Engine temperature above 158° F (70° C).
Altitude above 7,200 ft. (2,200 m).
Engine rpm over 3000

CONDITION 4
Engine temperature above 158° F (70° C).
Intake air temperature is above 122° F (50° C).
Engine rpm over 3000