Evaporative Emissions System: Description and Operation

Evaporative Emission Control System Schematic:

The evaporative emission control system used on this vehicle is the charcoal canister storage method. This method transfers fuel vapor from the fuel tank to an activated carbon storage canister to retain the vapors when the vehicle is not operating. When the engine is running the fuel vapor is purged from the carbon element by intake air flow and consumed in the normal combustion process.

Vapor Canister:

VAPOR CANISTER AND PURGE VALVE OPERATION
The purge valve is an integral part of canister. When the engine is running, manifold vacuum is supplied to the top of the purge valve (Control Vacuum Signal), which lifts the valve diaphragm and opens the valve. The lower tube on the purge valve (PCV tube) is connected to ported vacuum above the throttle valve. The rate of purge is controlled through this port by throttle position.