Evaporative Emissions System: Description and Operation

Evaporative Emission Control System:

PURPOSE
Controls hydrocarbon emissions from raw fuel.

OPERATION
The evaporative emission control system (EECS) consists of the fuel tank and filler cap, a check/relief valve, two roll-over/float valves, a vacuum switching valve and charcoal canister with integral purge control valve. The system collects fuel vapors that would otherwise be discharged into the atmosphere and temporarily stores them in a charcoal canister. When the engine is started, the vapors are directed to the intake to be burned in the engine. Canister purge is ECM controlled by means of a vacuum switching valve. This system of vapor recovery helps prevent raw hydrocarbon emissions and also promotes fuel economy by eliminating fuel loss through evaporation.