Evaporative Emissions System: Operation

Fuel vapors pass through the carbon canister and deposit hydrocarbons on the surface of the carbon. When the engine is running, fresh air entering the canister through an opening cleans the carbon and routes the hydrocarbons via the air cleaner back to the engine for combustion. On all fuel injected models, a fuel return line is used to prevent excessive pressure build-up at idle speeds.

Fig 1: Quantum Carbon Canister-to-Intake Manifold Flow

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.