Canister Vent Valve: Description and Operation

Canister Vent Valve

Except CODE (494a) USA Version

Models 129 As Of 04/01/98 Production Date





Vent valve design


Vent valve position
- In vent line between fuel tank and activated charcoal canister

Vent valve task
- Admitting and releasing air to/from fuel tank
- Preventing overfilling of fuel tank


Vent valve function
- Air release from fuel tank
The vent valve (4) opens at a pressure of 30 - 50 mbar: fuel vapors flow to the activated charcoal canister.
- Air admission to fuel tank
The air admission valve (6) opens at a vacuum of 1 - 16 mbar in the fuel tank. Air or fuel vapors are drawn in through the activated charcoal canister.
- Refueling
The opening pressure of the vent valve (4) of 30 - 50 mbar is not achieved when the fuel tank filler cap is removed. The vent line to the activated charcoal canister remains sealed off. The refueling nozzle switches off more rapidly.