Evaporative Emissions System: Description and Operation

Evaporative emission canister





Description

Hydrocarbons from the fuel tank are trapped in a container filled with activated charcoal and stored there when the engine is stationary.

When the car is driven, the EVAP canister purge valve opens and the fuel fumes are sucked into the engine and burnt. There are two versions of the purge valve: a vacuum-controlled valve (M1985-1987) and a solenoid valve (M1988-). The vacuum- controlled valve is operated via a hose from the throttle body while the solenoid valve is operated by the control module.

The valve opens when the engine load is such that combustion of the additional fuel can take place. The hydrocarbons pass via a hose to the intake manifold where they are burnt together with the regular fuel- air mixture.