Fuel Evaporation System: Operation
When the engine is not running, fuel tank vapors flow through vent line into canister for storage. Float bowl vapors flow through the outer vent control valve into canister for storage when the ignition key is off.
When the engine is running above 1,600 RPM and coolant temperature is above 131°F (55°C), the vacuum switching valve (VSV) opens and canister vapors are drawn into intake manifold for burning. The VSV is an electrically operated solenoid type valve and is opened and closed by a computer. This computer receives input signals from a speed sensor and thermo switch.