Evaporative Emission (EVAP) Systems: Notes

Overview 

The EVAP system prevents fuel vapor build up in the sealed fuel tank. Fuel vapors trapped in the sealed tank are vented through the vapor valve assembly on top of the tank. The vapors leave the valve assembly through a single vapor line and continue to the EVAP canister for storage until the vapors are purged to the engine for burning.

All applications required to meet on board diagnostics (OBD) regulations use the enhanced EVAP system. Some applications also incorporate an on board refueling vapor recovery (ORVR) system. Refer to the appropriate Evaporative Emissions article for vehicle specific information on the description and operation of the Evaporative Emission System.