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    Thread: Gravity valve for fuel vent...what problems can occur?

    1. Member
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      Things with wheels and engines...
      08-24-2004 05:04 PM #1
      So, that little gravity valve back by the fuel filler neck, what exactly does it do? If it does fail, what kind of problems does it cause?

      Just trying to learn a bit more about the fuel system...

      Thanks

      SteveO
      13 GolfR
      09 Audi A4
      94 Ford F250 IDI TD
      77 VW Rabbit (G60 Project)

    2. Member WackyWabbitRacer's Avatar
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      08-24-2004 06:09 PM #2
      The valve is actually a vent for the gas tank. It is called a gravity valve in the event the car rolls over, and the valve then closes to prevent gas from leaking out.

      If the valve is not functioning, then vapor pressure will build up inside the gas tank and cause gas to overflow pass the gas cap if the tank is relatively full.

      The valve is a part of the Evaporative Emission Control (EEC) system. Regards, WWR.

      WWR
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    3. Member
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      08-25-2004 12:04 AM #3
      Could a failing valve cause any adverse effects on the car running?
      SteveO
      13 GolfR
      09 Audi A4
      94 Ford F250 IDI TD
      77 VW Rabbit (G60 Project)

    4. Member WackyWabbitRacer's Avatar
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      08-25-2004 02:28 PM #4
      Quote, originally posted by 2Turbo4X4 »
      Could a failing valve cause any adverse effects on the car running?

      Don't believe so as the CIS fuel pump is gravity fed from the gas tank. The only problem with a failing valve is normally gas overflow from the gas cap if the tank is relatively full. Regards, WWR.

      WWR
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    5. Member dbreid's Avatar
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      08-25-2004 02:38 PM #5
      I had a gravity valve get destroyed once on a car I had. The strap holding it broke (rust) and the valve hit the top of the tire, wearing a huge hole in it. I tried to find another, but couldn't, so I just connected all the lines together without the valve, and never saw any issue. That car was carbed, though, which might make a difference?

      -Dan


    6. 08-25-2004 02:45 PM #6
      As WWR mentioned, the gravity part of that valve is only there to prevent leakage when the car is overturned. You wouldn't notice a difference taking it out until you landed on your roof and ended up in a puddle of gas.

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