Evaporative Emissions System: Description and Operation

Typical EEC-IV Evaporative Emission System:

PURPOSE
To reduce HC, the fuel vapors are vented from the fuel tank to the carbon canister and stored there until they can be purged to the engine for burning.

OPERATION
Fuel vapors trapped in the sealed fuel tank are vented through the orificed vapor valve assembly in the top of the fuel tank. The vapors leave the vapor assembly through a single vapor line and continue to the carbon canister (located in the engine compartment or along the frame rail) for storage until they are purged to the engine for burning. Purging the carbon canister is controlled by the powertrain control module, which opens the canister purge solenoid. Purging occurs when the engine is at normal operating temperature.