Fuel Evaporation System: Operation
When the engine is not running, fuel tank vapor passes through the roll-over valve and flows into the canister. When the engine is started and throttle opens above idle, a ported vacuum signal opens the purge valve and vapors are drawn into the intake manifold from canister.
A calibrated jet located in purge line to intake manifold meters the vapor flow into intake manifold. The roll-over valve prevents leakage in case of roll-over.