Evaporative Emissions System: Description and Operation

The evaporative emission system is used to reduce hydrocarbons emitted into the atmosphere from the fuel system. This reduction of hydrocarbons is accomplished by activated charcoals in the EVAP canister.

The fuel vapor in the sealed fuel tank is led into the EVAP canister which contains activated carbon. This is where the vapor is stored when the engine is not operating.

The vapor in the EVAP canister is purged by the air flowing through the EVAP canister purge volume control valve which is controlled by engine control module. When the engine operates the flow rate of vapor controlled by the EVAP canister purge volume control valve is proportionally regulated as the air flow increases.

The EVAP canister purge control valve shuts off the vapor purge line during decelerating and idling; under normal operating conditions the valve is usually open.