Evaporative Emissions System: Description and Operation

Fig.1 ORVR System Schematic:

EVAPORATION CONTROL SYSTEM
The evaporation control system prevents the emission of fuel tank vapors into the atmosphere. When fuel evaporates in the fuel tank, the vapors pass through vent hoses or tubes to an activated carbon filled evaporative canister. The canister temporarily holds the vapors. The Powertrain Control Module (PCM) allows intake manifold vacuum to draw vapors into the combustion chambers during certain operating conditions.

All engines use a proportional purge solenoid system. The PCM controls vapor flow by operating the purge solenoid.

NOTE:
- The evaporative system uses specially manufactured hoses. If they need replacement, only use fuel resistant hose. Also the hoses must be able to pass an Ozone compliance test.