Evaporative Emission Control Canister: Description and Operation

Evaporative emission canister







The evaporative emission canister is placed on the right-hand side of the tank and consists of a container filled with a special pelletized charcoal. Pelletized charcoal is used to give as little back pressure as possible from the canister. Hydrocarbons which have vaporised in the tank are passed through a line to the canister. During filling up, the hydrocarbons and air from the tank are evacuated via a line to the carbon filter which absorbs the hydrocarbons.

Lines connect the evaporative emission canister with the fuel tank, purge valve and shut-off valve. When the engine starts, air is drawn through the shut-off valve to the canister and then via the purge valve into the intake manifold. The hydrocarbons follow and are burned in the engine.

The evaporative emission canister absorbs around 70 g hydrocarbon per tank filling. During driving, the canister is purged; the time required for this depends on the driving style. The canister can absorb a maximum of around 125 g hydrocarbons.