Evaporative Emission Control System
1 - filler cap, 2 - charcoal canister, 3 - hose, 4 - calibrated hole, 5 - hose, 6 - cleaning solenoid valve, 7 - coolant temperature sensor, 10 - safety valve
To minimize leakage of unburned hydrocarbons into the atmosphere, later models use a fuel vapor control system. The fuel filler cap is sealed, so the charcoal canister collects the gasoline vapors generated in the fuel tank of a parked car. The canister stores fuel vapors until they are removed from the canister through the purge solenoid valve. When the valve is open, the fuel vapor passage to the engine air supply path is open and the vapors are burned while the engine is running.
To ensure that the engine is running properly, when the engine is cold or idling, the ECU does not open the purge control valve until the engine is warm and does not allow stored steam to pass into the engine air supply path.