Evaporative Emissions - Overview (G1772568): Overview

The Evaporative Emission (EVAP) system reduces the level of hydrocarbons released into the atmosphere by fuel vapor venting from the fuel tank. The system comprises of an Evaporative emissions canister, an Evaporative emissions purge valve, interconnecting vapor pipes and, on North American Specification (NAS) vehicles, a Diagnostic Module Tank Leakage (DMTL) pump and filter. The vapor pipes are connected to the system components using quick release connectors.

Fuel vapor is generated by the fuel in the tank and the amount of vapor produced increases as the fuel heats up. Fuel vapor can flow freely to the Evaporative emissions canister via the tank venting system.

The vapor generated in the fuel tank during refueling flows without restriction to the Evaporative emissions canister.

The vapor passes into the Evaporative emissions canister where it is absorbed and stored by the charcoal. Because there is a limit to the amount of vapor the canister can contain, the fuel vapor is purged from the canister when the engine is running and burned in the engine.