When Engine is Not Running

The fuel vapor taken up into the vapor separator is routed into the check and relief valve. When the vacuum becomes 1 - 1.4 in. Hg, the check valve opens and allows vapor into the crankcase. While the check valve is open, the valve at the air filter side remains closed to prevent flow of vapor into the atmosphere. On California models, the vent switching valve is opened to allow fuel vapor into the canister from the float chamber.