Fuel Evaporation System: Description
The Fuel Evaporation system is used to prevent fuel vapors (hydrocarbons) from entering the atmosphere. Activated charcoal in the carbon canister absorbs fuel vapors given off by the fuel system.
The system consists of a fuel tank with a positive sealing filler cap, carbon canister with purge control valve, fuel check valve, canister purge and vacuum signal lines, and vapor vent lines.
Vehicles use a thermal vacuum valve. In addition, Federal models use an evaporative purge control valve which controls purge air flow in proportion to intake air quantity.
Vehicles use a vent switching valve.