Fuel Evaporation System: Description

The purpose of the Evaporation Control System is to prevent gasoline vapors (hydrocarbons) from the fuel tank, carburetor and throttle body, from entering the atmosphere.

When fuel evaporates in the fuel tank, fuel bowl (carburetor models) or throttle body (EFI and turbo models), the vapors pass through vent hoses to a charcoal canister. The EFI system, having only 2 hoses to the throttle body, uses an in-line purge solenoid (opens when engine is running) to extract vapors from the canister.

The vapors are stored in the charcoal canister until they are drawn into the intake manifold after the engine begins to run. See Figure and Figure .