Evaporative Emissions System: Description and Operation: Overview

Overview
The Evaporative Emission (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 (located in the engine compartment, in the rear of vehicle near luggage compartment area or along the frame rail) for storage until the vapors are purged to the engine for burning.

There are two types of Evaporative Emission (EVAP) systems:
^ The Enhanced Evaporative Emission (EVAP) system.
^ The On-Board Refueling Vapor Recovery (ORVR) Evaporative Emission (EVAP) system.

NOTE: Refer to the Evaporative Emission System components for information for: fuel vapor control valve, fuel vapor vent valve assembly and fuel vapor separator assembly, liquid/vapor fuel discriminator, fuel filler pipe check valve, fill limit valve assembly, fill limit vent valve assembly, fuel filler pipe flapper valve, fuel vapor control valve (fuel tank mounted), ORVR T-connector assembly and EVAP canister.