Venting system USA:

The fuel tank is vented during refueling via the refueling vent line.

Because of its large cross-section, the refueling vent line directs the displaced volume (fuel vapors) at high speed through the condensate tank to the carbon canister.

The activated carbon retains the fuel contained in the fuel vapors. The cleaned air is discharged to atmosphere via the evaporation line, the tank leakage diagnostic module and the dust filter.

During driving, the system tank is vented in the same way via the refueling vent line and service vent lines.

The condensed constituents of the fuel vapors pass from the condensate tank via the service vent lines back into the fuel tank.

The roll-over valves in the vent lines prevent fuel from flowing into the condensate tank in extreme driving situations and positions.

The flow restrictor in the right service vent line prevents overfilling of the fuel tank during refueling. When the specified fill quantity is reached, the roll-over valve in the refueling vent line closes. The tank is now only vented via the service vent lines. If refueling is now continued, the flow restrictor generates an overpressure in the fuel tank. This significantly prevents further filling of the tank. The pressure holding valve in the left service vent line limits the overpressure in the fuel tank.

The carbon canister is regenerated by purging with fresh air.

The engine control unit opens the tank vent valve. Thus the vacuum pressure of the engine intake manifold is applied at the purge line.

In this way, the carbon canister is purged by the supply of fresh air via the tank leakage diagnostic module and the dust filter. The fuel constituents bound by the activated carbon are flushed out by the supplied air and directed via the purge line to the engine for combustion.

This operation is only possible while the engine is running.