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Fuel Tank Vent: Description and Operation




GF47.30-P-3100MOR Component Description For The Vent Valve
- MODEL 230.477 with ENGINE 275.954 as of Model Year 09 /AEJ 08 model refinement package
- except code (494) USA version
- MODEL 230.479 with ENGINE 275.981 as of Model Year 09 /AEJ 08 model refinement package
- except code (494) USA version





View of underfloor behind rear axle
76 Vent valve

Location
The vent valve is located under the fuel tank.

Task
The vent valve aerates and ventilates the fuel tank, and also prevents overfilling.

Design
The vent valve consists of a plastic housing with integrated aeration/ vent valves.

Function
Fuel tank aeration
The aeration valve opens at a vacuum of about 1 to 16 mbar and the air and fuel vapors are extracted through the activated charcoal canister.

Fuel tank ventilation
The vent valve opens at an overpressure of about 30 to 50 mbar and the fuel vapors can flow to the activated charcoal canister.

Refueling
The vent valve opening pressure of about 30 to 50 mbar is not reached when the tank cap is removed. The vent line to the activated charcoal canister remains closed off. This causes the fueling nozzle to shut off more quickly, and prevents overfilling.

By overfilling, the fuel can get into the activated charcoal canister and can be suctioned by the engine.