Evaporative Emissions System: Operation
When the engine is stopped, fuel vapors flow from the float bowl through the open solenoid valve down into the canister. Vapors from gas expanding in the fuel tank pass through the vapor separator, 2-way valve and into the canister. The purge line check valve is closed to prevent vapors from rising in the line and entering the intake manifold.
When the ignition is turned on, the solenoid valve closes, blocking off the float bowl-to-canister passage. The thermal vacuum valve vents control vacuum to the air cleaner until the engine reaches temperature above 95° F (35° C). Above the switching point, vacuum is applied to the purge control valve. Manifold vacuum pulls fresh air into the canister, through the purge line and into the intake manifold. This fresh air purges the fuel vapors from the canister.