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Thread: Some fuel tank pressure problems

  1. #1
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    Some fuel tank pressure problems

    Hey guys.
    After having the car stand for 3 weeks I decided to start it. After I did I found a huge puddle of fuel in the garage. Got me scared. Did some searching and found no leak later. All clamps good and I changed the fuel hoses couple of years ago.
    No leak after that.

    Then when I opened the gas cap the next day I got this massive hissing. Like some vacume.
    Now the question is what should I tackle?
    I have my car almost in perfect shape mecanically

  2. #2
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    Try here Andre, Sounds like the vent valve in the rear of the car.


    Cabin fuel smell & E31 fuel ventilation system




    - - - Updated - - -

    .
    Attached Images Attached Images
    Last edited by 8eights; 01-08-2018 at 01:04 PM.

  3. #3
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    That valve is No Longer Available (hasn't been for several years)
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  4. #4
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    Isn't there one available with a extra outlet that needs to be plugged? I found a picture TX.



    part# 16131182761
    Last edited by 8eights; 01-08-2018 at 02:18 PM.

  5. #5
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    Any thoughts on whether this could also be the culprit for my problem filling up at the pump? Gas doesn't flow freely and overflows, cutting the pump off. It takes me 30 minutes to gas up. Very irritating.

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  6. #6
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    That is why you need so long at the fill up - fuel tank can’t vent except for the filler tube,, which shuts off the flow from the fuel delivery pump at the station. There is a 3-port vent from another model that can be used, just plug the unused port.
    '93 850Ci - Mineralweiß Metallic

    2001 740iL - Titansilber
    ALPINA B7 -Alpinweiß III


    ...the price of cool ain't cheap!

  7. #7
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    Quote Originally Posted by TxGR8White View Post
    That is why you need so long at the fill up - fuel tank can’t vent except for the filler tube,, which shuts off the flow from the fuel delivery pump at the station. There is a 3-port vent from another model that can be used, just plug the unused port.
    Any idea from which model and year?

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  8. #8
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  9. #9
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    What da? Glad they're available...not happy about the price.
    1993 850Ci.....18 years & 165,000 miles and counting!

  10. #10
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    I just bit the bullet and bought one. Thanks for the lead.

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  11. #11
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  12. #12
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    Don't bother with either of those places. NLA....still.


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  13. #13
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    Quote Originally Posted by nrp22101 View Post
    Don't bother with either of those places. NLA....still.


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    Bummer!
    1993 850Ci.....18 years & 165,000 miles and counting!

  14. #14
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    I don't think we will suffer here, There are alternatives with other BMW's using a similar part or a far durable performance part by Jegs/Earls or Russel.

  15. #15
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    I very much doubt this is your problem (filling gas tank). This valve breaths into the charcoal canister via a long small hose that I doubt can keep up with the flow of fuel into the gas tank. I do think it is the cause of the hissing you hear when opening the gas tank (mine does the same thing).
    I believe there is a much shorter and fatter breather hose for the gas tank that leads to the neck of the fill tube. This allows air to escape as you fill the tank and in your case is perhaps blocked or damaged.

  16. #16
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    Quote Originally Posted by BMSman View Post
    I very much doubt this is your problem (filling gas tank). This valve breaths into the charcoal canister via a long small hose that I doubt can keep up with the flow of fuel into the gas tank. I do think it is the cause of the hissing you hear when opening the gas tank (mine does the same thing).
    I believe there is a much shorter and fatter breather hose for the gas tank that leads to the neck of the fill tube. This allows air to escape as you fill the tank and in your case is perhaps blocked or damaged.
    Hmmm. Thanks BMSman, I'll give it a look.

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  17. #17
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    Quote Originally Posted by 8eights View Post
    I don't think we will suffer here, There are alternatives with other BMW's using a similar part or a far durable performance part by Jegs/Earls or Russel.
    Do you have a suggestion for a replacement part? I need mine replaced as well but not sure where to look.

  18. #18
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    Quote Originally Posted by cayle View Post
    Do you have a suggestion for a replacement part? I need mine replaced as well but not sure where to look.

    Anyone resolved a replacement part for the vent unit?

    What about the Mercedes Fuel Tank Vent Valve - part number 123 470 03 93 with an external rollover valve?

  19. #19
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    Nissan 1737089910

    Quote Originally Posted by Nkana View Post
    Anyone resolved a replacement part for the vent unit?

    What about the Mercedes Fuel Tank Vent Valve - part number 123 470 03 93 with an external rollover valve?

  20. #20
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    Would this work on our car?

  21. #21
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    It should and only one in and outlet, More like our original part and plenty available.

  22. #22
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    After a bit more research I found this one is a little less expensive (I paid $30 shipped). It does exactly the same job as the original part and is about the same size. I made a simple bracket out of aluminum so it bolts up to the existing mounting point.

    The purpose of this valve is to allow the gas tank to breath (in and out) but prevent fuel flowing back down this line in the event of a vehicle roll over. The gas tank will breath 'in' as fuel is drawn out and breath 'out' as fuel expands due to changing ambient heat. It breaths in/out via the charcoal canister in the engine bay which traps any gas vapors. The charcoal canister is purged by the engine on start up (fumes drawn into intake manifold). The valve allows the gas tank to breath in with little resistance but exhaling requires it overcome a small pressure barrier.

    The Nissan part is clearly labelled 'UP' and the connections 'Tank' and 'Engine', so there is no confusion as to how it should be installed. The oem BMW part looks like a standard valve you see mounted in the top of a gas tank that is now mounted in a white plastic carrier. The gas tank connection is to the bottom of the BMW valve and the charcoal canister to the top.

    fueltankvalve.JPG

    ftb2.JPG

    ftb3.jpg

    The nipples on the Nissan part are a bit smaller than the BMW part which uses 8x13 fuel hose.. This Nissan part is designed for 6x12 fuel line. After applying some heat to 6 x12 hose I was able to squeeze it over the connections in the car. Note the valve connections (top/bottom) are reversed when compared to the BMW part.
    Last edited by BMSman; 03-04-2018 at 02:30 PM.

  23. #23
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    They do work, You can also drill 2 tight holes and snap it into place, I'm using the other part number you provided................... 1737089910

  24. #24
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    Quote Originally Posted by 8eights View Post
    They do work, You can also drill 2 tight holes and snap it into place, I'm using the other part number you provided................... 1737089910
    Did you find the hose connections smaller than the BMW part?

  25. #25
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    I was looking at my valve yesterday, keep in mind that the input is the lower nipple and the output is the upper one. Mine still operated fine when some compressed air applied to the bottom, not too much pressure but I could see how it worked.

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