Evaporative Emissions System: Description and Operation

PURPOSE

The evaporation control system prevents the emission of gasoline vapors from the fuel tank into the atmosphere.

OPERATION

When fuel evaporates in the fuel tank, the vapors pass through vent hoses or tubes to a carbon filled evaporative canister. The vapors are temporarily held in the canister. When the engine is operating, the vapors are drawn into the intake manifold.

The vapors are drawn into the engine at idle as well as off idle. This system is called a Bi-level Purge System where there is a dual source of vacuum to remove fuel vapor from canister. The source of vacuum at idle is a tee in the PCV system. Refer to the appropriate Engine Vacuum Schematic.

The evaporative canister is a feature on all models (with gas engines) for the storage of fuel vapors from the fuel tank.

Only use fuel resistant hose when replacing evaporation control system hoses.