Evaporative Emissions System: Description and Operation

Fig.35 Charcoal canister.:

Fig.36 Two way valve.:

The evaporative emission control system is employed to prevent evaporative fuel in the fuel tank from being discharged into the atmosphere.
Components for the system consist of a charcoal canister, FIG. 35, two way valve, FIG. 36, purge control valve, thermal vacuum valve, solenoid valve, check valve and vapor sperator.
Fuel vapor evaporated from the fuel tank is routed into the canister located in the engine compartment. When the engine is idling, this vapor is stored in the canister because the purge valve on the canister is closed by the force of high intake vacuum. During this time, the vpaors are absorbed in the charcoal particles.
As the engine speed increases, the purge valve opens. The absorbed vapor is drawn from the canister into the intake manifold through the open purge valve and purge hose. While the purge valve is open, fresh air is drawn into the canister through the bottom filter, purging the absorbed vapor from the charcoal. When the engine is not running, the purge valve is opened by the return spring but the vapor remains in the canister because there is no vacuum to draw the vapor out.