Fuel Evaporation System: Operation

When engine is not running, fuel vapor from tank vents through, or tank pressure control valve, depending on model, into charcoal canister. On carbureted models, the vent switching valve opens to allow carburetor vapor to vent to charcoal canister. Purge control valve is closed when engine is not running.

When engine is running, vent switching valve closes by solenoid action (if equipped). Purge control valve opens on vacuum signal from distributor advance mechanism and allows canister vapor to be drawn into intake manifold.