Fuel Evaporation System: Operation
When the engine is not running, fuel vapor from the fuel tank is directed to the charcoal canister, to be stored. The tank pressure control valve is closed preventing vapors from escaping into the atmosphere. At the same time, the vent switching valve is open allowing fuel vapors from the float bowl to the charcoal canister, where they are stored.
When the engine is running, the vent switching valve closes and manifold vacuum opens the tank pressure control valve, allowing fuel vapors from the fuel tank and charcoal canister to flow to the intake manifold to be burned by the engine.