Vacuum/Thermostatic Bowl Vent Valve

Fig. 52 Vacuum/thermoststic bowl vent valve:

This valve, Fig. 52, used on some vehicles, is a vacuum/temperature operated on/off valve. This valve controls vapor flow from the carburetor bowl to the carbon canister. When the engine is running, manifold vacuum closes the flow path from the carburetor bowl to the carbon canister. This valve also closes the bowl to canister flow path when the temperature of the valve is less than 90° F even if there is no manifold vacuum. When the temperature of the valve exceeds 120° F, the valve is open except when closed by manifold vacuum.