The Fuel Evaporative Emission Control (EVAP) System temporarily absorbs the evaporated gas in the charcoal canister and channels it to the engine for burning, in order to prevent the fuel, which is evaporated from the fuel tank, from escaping into the atmosphere.
The evaporated gas, which is generated in the fuel tank, opens the check valve (1) and flows into the canister. The charcoal absorbs the evaporated gas in the canister. The absorbed gas is drawn from the purge port of throttle body into the cylinder to burn while the engine is running. For some models, the engine ECU controls the gas flow by controlling the opening of the VSV (for EVAP). The check valve (2) and the vacuum valve of the fuel tank cap open to draw the outside air into the tanks when the inside of tank becomes a vacuum (because the outside temperature is low, etc).
(EVAP) System for North American Models
North American models have a feature that keeps evaporated fuel from escaping during refueling, by temporarily absorbing it into the charcoal canister. There also is a diagnostic function.
When opening fuel tank cap
The atmosphere is drawn into the chamber located in the upper of the ORVR valve.
The ORVR valve opens and the evaporated gas flows into the canister when the pressure in the tank increases by refueling.