Fuel Evaporation System: Operation
When the engine is off, the float bowl vent valve opens. The fuel vapors from the fuel tank and carburetor collect in the charcoal canister. When the engine is running, the float bowl vent valve closes and engine vacuum is applied to the canister. This draws ambient air through the purge valve, canister, and canister purge line into the carburetor.
A fuel recirculation system prevents fuel in the lines from absorbing engine compartment heat, minimizing the possibility of fuel evaporation. See Fig 1 .