Evaporative Emissions System: Description and Operation

Evaporative Emission Control System:

EVAP Operations Chart:

This system is designed to minimize the amount of raw fuel vapors escaping into the atmosphere, and consists of a charcoal canister, an outer vent control valve, an electronic control unit (ECU) controlled vacuum switching valve (VSV) and fuel tank filler cap with a check valve. The system uses the charcoal canister to store fuel vapor when the engine is not running. When the ignition is turned off, the outer vent control valve is opened allowing vapor to vent into the charcoal canister. The ECU monitors engine speed, throttle position, water temperature and opens the VSV when the conditions are correct for purging of the charcoal canister and fuel tank. The check valve in the fuel cap allows air to enter the tank, thus preventing tank deformation and allowing clean air to sweep through the tank.