Evaporative Emissions System: Description and Operation

Crankcase And Evaporative Emission Control System (PCV & EVAP):

The evaporative emission control system stores fuel vapor generated in the fuel tank in the canister when the engine is not running. The fuel vapor is stored in the canister until it is drawn into the dynamic chamber and burned when the engine is started.
To control crankcase emissions when the engine is running at idle the purge control valve is opened slightly and a small amount of blowby gas is drawn into the combustion chamber and burned. At high engine speed or heavy-load condition the purge control valve is further opened and a larger amount of blowby gas is drawn into the combustion chamber.