Fuel Evaporation System: Operation
Fuel vapor from the sealed fuel tank is stored in the charcoal canister when the engine is stopped or idling. As the throttle valve opens and engine speed increases, vacuum opens the purge control valve and fuel vapors are drawn from canister into the intake manifold.
On Pickup with fuel injected 2.4L engine, a thermal vacuum valve prevents any purging of canister by preventing the opening of the purge valve when coolant temperature is below 140°F/60°C.
When the purge valve is closed a small amount of purge air flows into intake manifold through the constant purge orifice.
On carburetted Pickup models, a vent switching valve allows carburetor float bowl to vent into canister when engine is not running.