Evaporative Emissions System: Description and Operation

Evaporative Emissions Control System Schematic:

SYSTEM DESCRIPTION

The Evaporative Emission Control System (EECS) 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. This retains the fuel 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 is consumed in the normal combustion process.

Vapor Canister:

VAPOR CANISTER

The canister has an integrated diaphragm operated purge valve. When the engine is running, manifold vacuum is supplied to the top of the purge valve (Control Vacuum Signal) which activates the valve diaphragm. The valve opens when the throttle is above a specified opening. The lower tube on the purge valve (PCV Tube) is connected to a timed port above the throttle valve. The purge rate is controlled by throttle opening position.