Evaporative Emissions System: Description and Operation

Evaporative Emissions 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:

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