Evaporative emission canister (Emission control)

Evaporative emission canister

The evaporative emission (EVAP) canister contains charcoal which absorbs and stores fuel vapour from the fuel tank while the engine is not running. When the engine is running the vapour is purged from the canister into the engine and burned.

The EVAP canister is purged when the EVAP canister purge valve is opened. Manifold depression draws fresh air into the canister through the charcoal, which releases fuel vapour into the throttle housing.

Evaporative emission canister purge valve

The EVAP canister purge valve is operated by the ECM. The valve remains closed when the engine is cold or at idling speed, to protect engine tune and catalyst performance. If the EVAP canister was purged during cold running or at idling speed, the additional enrichment in fuel mixture would delay catalyst light off time and cause erratic idling. When the engine is above 75˚C, the purge valve solenoid will become operational (modulated ON and OFF) whenever the engine speed is above approximately 1800 rev/min. When the purge valve is opened, fuel vapour from the EVAP canister is drawn into the throttle housing for combustion.