Evaporative Emission Control Canister: Description and Operation

OPERATION

Depending on engine displacement, either one or two EVAP canisters may be used. Also depending on vehicle model and fuel tank size, the canisters may be mounted either vertically or horizontally.

The ESIM (Emission System Integrity Monitor) switch is mounted to the EVAP canister. The NVLD system is no longer used on any engine.

The EVAP canister(s) are filled with granules of an activated carbon mixture. Fuel vapors entering the EVAP canisters are absorbed by the charcoal granules.

Fuel tank pressure vents into the EVAP canisters. Fuel vapors are temporarily held in the canisters until they can be drawn into the intake manifold. The duty cycle EVAP canister purge solenoid allows the EVAP canisters to be purged at predetermined times and at certain engine operating conditions.