Evaporative Emissions System: Operation

Fuel vapors pass from the tank into the charcoal canister, where they are absorbed by activated charcoal. When the engine is running, vacuum is pulled through the canister, purging the fuel vapors. The 2-way valves provide air to vent the fuel tank and act as a safety valve to prevent tank over-pressure from fuel expansion. Turbo models use a check valve in the purge line to prevent the turbocharger from pressurizing the canister.