Canister Control Valve

Two types of canister control valve are used. One type acts as fuel bowl vent and canister purge. When engine is not running, spring tension holds valve open allowing venting of float bowl. When engine is running, manifold vacuum pulls plunger up to close valve.

The other type of valve acts as both vapor vent valve and purge valve. When engine is running, manifold vacuum from PCV system pulls lower diaphragm upward. This turns off venting of carburetor float bowl. When engine is operating above idle speed, control vacuum pulls upper diaphragm upward. This allows purging of canister through PCV system.