Fuel Evaporation System: Operation
When the engine is not running, fuel tank vapors pass through the 2-way and 1-way valves and flow 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 check valves in fuel lines allow vent air to enter the tank to replace fuel being drawn out, and also to prevent leakage in case of rollover.