Fuel Evaporation System: Operation

When fuel evaporates in carburetor float chamber or fuel tank, vapors pass through vent hoses or tubes to the charcoal canister.

Fuel vapors are held on the activated charcoal surface until they are drawn into the intake manifold (when the engine is running). Vacuum port in carburetor base controls vapor flow to engine.

Fuel vapors from primary canister are purged through carburetor port. When distributor vacuum signal activates purge switch, vapors from secondary canister are purged through PCV hose to carburetor.

Damping canister is used on "H" and "K" models with 2-canister system. It cushions sudden releases of fuel vapors when purge control valve opens. Fuel vapors are held in canister and gradually released into intake manifold.