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Thread: Gas Neck O-Ring Fell Off!

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    Gas Neck O-Ring Fell Off!

    Hi all, 1995 525i 5SPD 280k

    Yesterday I poured some Gummout multi purpose cleaner in the gas tank but, I noticed a green o-ring inside the neck. It seemed off centered. I pulled it out before it fell down in the neck. Now when I am near the passenger side rear wheel I smell gas fumes. Is there a way to put the o-ring back? I'm not sure what the purpose of the o-ring is for and the next time I add gas I don't want it to leak on the ground.

    Thanks in advance..

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    That's interesting. I had to open the spring loaded flap in order to pour the Gummout solution. When I opened the flap, I saw a portion of the green O-ring as if it moved out of position.I quickly grabbed it in case it might fall in the neck the next time I add fuel. I will take a pic when I get home this afternoon. I think the O-ring is about an 1 1/2 inch in size. Maybe it goes to the gas cap? I don't know but, it was odd to see it on the other side of the flap.

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    There is no o ring in the fuel neck. There is also no typical o ring on the gas cap - if there was one and it came off it would surely be torn.

    I'm going to guess, that what you have is a bad gas cap, and a PO who solved the venting vapour problem temporarily by putting in the O ring on the filler neck. A nice hack but gas caps are cheap and last forever usually and yes that O ring could fall into the tank.

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    Quote Originally Posted by alang1990 View Post
    There is no o ring in the fuel neck. There is also no typical o ring on the gas cap - if there was one and it came off it would surely be torn.

    I'm going to guess, that what you have is a bad gas cap, and a PO who solved the venting vapour problem temporarily by putting in the O ring on the filler neck. A nice hack but gas caps are cheap and last forever usually and yes that O ring could fall into the tank.
    That's interesting. The cap seems fine, from what I see. it's just odd that the O-ring was on the other side of the spring loaded flap. The O-ring is actually a little bigger than the flap hole. I never smelled gas fumes before until I pulled out the O-ring. Now I can smell gas fumes in that area. I'm baffled on how the o-ring was on the other side of the flap. It looked as if the o-ring moved out of position. When I opened the flap, I saw a third of the o-ring exposed in the hole and the rest of the o-ring wasn't visible. I grabbed needle nose pliers and pulled the o-ring out. it looked as if it slid out from the side of the neck on the side where the flap door opens. Really odd.. I'll go to the car on my lunch break and take a pic of the O-ring.

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    IMG_0212.jpg
    This is the O-ring that was protruding from the side under the spring loaded flap..
    Any ideas what this is to?
    Thanks in advance..

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    Just a thought. Possibly gas was added using a plastic gasoline can and somehow the nozzle had this o ring that got snagged pulling the nozzle past the flap?? Just a thought. Cheers, George

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    Quote Originally Posted by chislern View Post
    Just a thought. Possibly gas was added using a plastic gasoline can and somehow the nozzle had this o ring that got snagged pulling the nozzle past the flap?? Just a thought. Cheers, George
    I have no idea... It was weird how it protruded. Basically, if you take your finger, push down the spring loaded flap, the o-ring stuck out about a 3rd. Funny thing is, when I relieved pressure from the flap, the o-ring prevented the flap from closing. I never seen the o-ring before. Out of all the times I pumped gas, I never seen the o-ring. I didn't notice the o-ring when I poured the Gummout, until I opened the flap.

    Technically, if the o-ring is visible when the flap is opened and when the flap attempts to shut the o-ring will prevent it from shutting, right? That would mean the flap was always ajar because the o-ring was in the way but, I remember the flap always being closed prior to pumping gas. I always look in the filler hole to make sure there's no debris in the entrance. It honestly looks like that o-ring fits between the cap fastener and the filler neck, as if it's two pieces.
    According to Moroza it's only one piece but, why all of a sudden I smell gas fumes around the gas cap door and rear passenger wheel?

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    Weird. But then your car's notorious for throwing curveballs. Is your gas cap sealing?

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    That O-ring has nothing to do with the fuel system. Green ones are typically used in air conditioning applications.
    If I had to make a story I'd say that fuel was added from a(probably dirty)container having this O-ring in it from another job.
    No worries, that is what the pick-up screen and filter are for.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

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    The gas cap has large thick rubber washer that is squeezed against the filler neck when the gas cap is turned in the neck. This creates a full seal. Your gas cap is damaged you need to get another. Considering that with the o ring there were no fumes but without there are fumes, its likely that it was put there on purpose by someone as a temp fix, rather than falling in as an accident.

    Forgot about the pickup screen at the bottom of the fuel filter. No risk to the car of any objects falling into the tank.

    Anyway, just to be thorough, there are two other situations where you will smell fumes from the back while standing outside the car. The first is if you fill up right to the top of the filler neck. Fuel will leak out through the breather hose attached to the fuel tank. This can't and shouldn't be fixed - the breather tub prevents overpressure in the tank. Second if there are cracks at the top of your fuel level sender, you will have fuel and fumes leaking out during a full fillup. That can be fixed with a light dusting of plastic glue plumbers use for pvc pipes.

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    Fumes
    There is a vapor/overflow tank and venting plumbing up in the rear quarter panel. One of the tubes is attached to the filler pipe. Two more, I believe, to the side of the tank on that side.
    If you remove the inner fender you can examine.
    A rusty fuel tank in New York isn't a stretch of the imagination either.
    Last edited by ross1; 10-18-2018 at 08:47 AM.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

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    Quote Originally Posted by moroza View Post
    Weird. But then your car's notorious for throwing curveballs. Is your gas cap sealing?
    It was fine until I noticed that o-ring on the inside of the spring loaded flap. Once I removed the o-ring, I can now smell fumes. I never smelled fumes prior to that. Very odd..

    - - - Updated - - -

    Quote Originally Posted by ross1 View Post
    Fumes
    There is a vapor/overflow tank and venting plumbing up in the rear quarter panel. One of the tubes is attached to the filler pipe. Two more, I believe, to the side of the tank on that side.
    If you remove the inner fender you can examine.
    A rusty fuel tank in New York isn't a stretch of the imagination either.
    I looked under to examine the fuel tank and it's fine. I will remove the wheel well lining to inspect. It was very odd to see that o-ring sticking out when i pushed the flap open.

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    Does the flap fully close and seal the filler neck? A friend of mine had a flap that was bent and gas fumes were very noticeable.

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    Quote Originally Posted by alang1990 View Post
    The gas cap has large thick rubber washer that is squeezed against the filler neck when the gas cap is turned in the neck. This creates a full seal. Your gas cap is damaged you need to get another. Considering that with the o ring there were no fumes but without there are fumes, its likely that it was put there on purpose by someone as a temp fix, rather than falling in as an accident.

    Forgot about the pickup screen at the bottom of the fuel filter. No risk to the car of any objects falling into the tank.

    Anyway, just to be thorough, there are two other situations where you will smell fumes from the back while standing outside the car. The first is if you fill up right to the top of the filler neck. Fuel will leak out through the breather hose attached to the fuel tank. This can't and shouldn't be fixed - the breather tub prevents overpressure in the tank. Second if there are cracks at the top of your fuel level sender, you will have fuel and fumes leaking out during a full fillup. That can be fixed with a light dusting of plastic glue plumbers use for pvc pipes.
    That's the thing.. I never smelled fumes prior to pulling out the o-ring. It's hard to believe the gas cap coincidentally became damaged right after I pulled out the o-ring. My gas cap doesn't click after tightening. The more you tighten it, the harder it will be to loosen it. I don't think the cap is damaged. There's a rubber housing around the entrance of the filler neck, where the cap screws into. Maybe I should remove the rubber housing and inspect.

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    Quote Originally Posted by chislern View Post
    Just a thought. Possibly gas was added using a plastic gasoline can and somehow the nozzle had this o ring that got snagged pulling the nozzle past the flap?? Just a thought. Cheers, George
    If that were the case, wouldn't the o-ring just fall down the neck, especially after all the times I filled the car with gas? Why would it be sticking out as if it were pinched between something inside the neck or it slid out of position?
    No one fills my tank, only me. I use Gummout Multi purpose cleaner every 5 months to keep the injectors clean. I use a pen to push down the flap and pour in the cleaner. I've never seen that o-ring before and I never used a gas tank to pour gas in the filler neck. It baffled me to see that and where I live, I don't think anything malicious occurred.

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    Quote Originally Posted by drewusmaximus View Post
    It was fine until I noticed that o-ring on the inside of the spring loaded flap. Once I removed the o-ring, I can now smell fumes. I never smelled fumes prior to that. Very odd..

    - - - Updated - - -



    I looked under to examine the fuel tank and it's fine. I will remove the wheel well lining to inspect. It was very odd to see that o-ring sticking out when i pushed the flap open.
    Forget about that O-ring. it's a red herring

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

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    Quote Originally Posted by ross1 View Post
    Forget about that O-ring. it's a red herring
    Agreed but, it's very odd.. I'm shocked it didn't fall down the neck and I never noticed it. Oh well... Moving forward.

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    I agree with ross1. Sometimes things happen in the universe we are not meant to know or understand!!

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    Quote Originally Posted by chislern View Post
    I agree with ross1. Sometimes things happen in the universe we are not meant to know or understand!!
    That is absolutely true! LOL It just sucks not finding out the reason. I guess i'll never know... LOL

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    Quote Originally Posted by drewusmaximus View Post
    That is absolutely true! LOL It just sucks not finding out the reason. I guess i'll never know... LOL

    Well now you have a new fume problem you did not have before. How are you planning to fix that?

    The o ring was, clearly a part of the solution to that.

    Please post some pictures of your filler neck, the o ring and your gas cap . Close ups.

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    Quote Originally Posted by alang1990 View Post
    Well now you have a new fume problem you did not have before. How are you planning to fix that?

    The o ring was, clearly a part of the solution to that.

    Please post some pictures of your filler neck, the o ring and your gas cap . Close ups.
    Not sure what I'm going to do yet.
    IMG_0217[1].jpg

    IMG_0218[1].jpg

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    Quote Originally Posted by alang1990 View Post
    Well now you have a new fume problem you did not have before. How are you planning to fix that?

    The o ring was, clearly a part of the solution to that.

    Please post some pictures of your filler neck, the o ring and your gas cap . Close ups.
    Coincidence. NO O-rings in the fuel tank filler or venting.
    This was debris caught in the leaded fuel restrictor flap, nothing more.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

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    Quote Originally Posted by ross1 View Post
    Coincidence. NO O-rings in the fuel tank filler or venting.
    This was debris caught in the leaded fuel restrictor flap, nothing more.
    Accepted solution. On to the next..

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    Quote Originally Posted by alang1990 View Post

    Anyway, just to be thorough, there are two other situations where you will smell fumes from the back while standing outside the car. The first is if you fill up right to the top of the filler neck. Fuel will leak out through the breather hose attached to the fuel tank. This can't and shouldn't be fixed - the breather tub prevents overpressure in the tank. Second if there are cracks at the top of your fuel level sender, you will have fuel and fumes leaking out during a full fillup. That can be fixed with a light dusting of plastic glue plumbers use for pvc pipes.
    No, if fuel leaks you have a problem. the tank is vented to the filler and a tank in the quarter panel, should be no leaks from there, ever.
    There IS a drain in the fuel door compartment intended for rainwater. You'll need to try pretty hard to over fill it that much.

    alang, you have an interesting transmission in that 1990 525
    Last edited by ross1; 10-18-2018 at 06:51 PM.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

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