Evaporative Emissions System: Description and Operation

GENERAL INFORMATION
The evaporative emission control system prevents fuel vapors generated in the fuel tank from escaping into the atmosphere.
Fuel vapors from the fuel tank flow through the fuel tank pressure control valve and vapor pipe/hose to be stored temporarily in the EVAP canister. When the vehicle is in operation, fuel vapors stored in the EVAP canister flow through the EVAP purge solenoid and purge port and go into the intake manifold plenum to be sent to the combustion chamber.
When the engine coolant temperature is low or when the intake air quantity is small (when the engine is at idle, for example), the engine control module brings the EVAP purge solenoid into the OFF state to shut off the fuel vapor flow to the intake manifold plenum. This does not only insure the driveability when the engine is cold or running under low load but also stabilize the emission level. Furthermore, an EVAP ventilation solenoid is locate between the EVAP canister and the atmosphere in order to carry out OBD-II EVAP leak monitoring. This solenoid is normally off, but turns on during OBD-II EVAP leak monitoring to shut off the flow of air into the EVAP canister from the atmosphere. Also, fuel vent valve is provided at fuel filler tube to prevent fuel from being over-filling to a fuel tank.