Canister Control Valve (CCV)

NOTE: See EMISSION COMPONENTS article for view of type 1, 2 and 3 control valves.

There are 3 types of canister control valves. In some applications, more than one type may be used on the same system.

The type 1 control valve is used on carbureted models. during periods when the engine is not running, vapors from the float bowl are vented through the valve to the canister. When the engine is started, manifold vacuum pulls the internal diaphragm upward, sealing off the float bowl. At this time only the carbon canister is purged.

The type 2 control valve is an integral part of the carbon canister. When the engine is not running, vapor from the fuel tank is stored in the carbon canister. When the vehicle is started, vacuum to the upper port will draw in the internal vacuum diaphragm, opening the port between the canister and purge vacuum.

The type 3 control valve is quite similar to the type 2 valve except that it is located in the canister purge lines itself. When vacuum is applied to the upper port of valve, diaphragm is lifted, opening port between purge vacuum and accumulated vapors. When engine is off, valve diaphragm is closed by internal spring pressure, preventing vapors from venting to atmosphere.