General Information

Evaporative Emission System

=> [ Function ]

• Hose connections are secured with either spring type or clamp type clips.

• Hose clip pliers (VAS 6340) or hose clip pliers (VAS 6362) are recommended for installing space saving clamps.

The connectors for fuel, vacuum and ventilation lines are marked with colors. There is either a colored dot on the connector or the release button is the corresponding color.





Function

Depending on air pressure and ambient temperature, varying quantities of fuel vapors form above the fuel surface in the fuel tank.

The Evaporative Emission (EVAP) system prevents these Hydrocarbon (HC) emissions from entering the atmosphere.

Fuel vapors travel from the highest point of the tank via the pressure retaining valve, with quantity restrictions, to the EVAP canister.

The activated charcoal in the canister stores these gases like a sponge.

While driving, with oxygen sensor control active (engine warm), the EVAP canister purge regulator valve (N80), (also called the regeneration valve) is activated by the Engine Control Module (ECM) in pulses dependent on load and engine speed. The opening time is dependent on input signals.

When purging (recovery of the activated charcoal), the suction tube vacuum sucks fresh air in through the ventilation opening on the underside of the EVAP canister. The fuel vapors stored amongst the activated charcoal and fresh air are proportionately supplied to be burned.

The pressure retention valve prevents fuel vapors from being sucked out of the tank when the EVAP canister purge regulator valve is opened and an intake manifold vacuum is present. It therefore ensures that the evacuation of the EVAP canister has priority.

When no voltage is applied (for example, wiring open circuit), the solenoid valve is closed. The EVAP canister is not purged.