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Thread: Fuel Smell

  1. #1
    Chuck Miller

    Fuel Smell

    I've been dealing (or NOT dealing) with a slight fuel
    smell inside my relatively stock 73'S since I bought it
    in 89'. Sometimes stronger then other times, a little stronger with the window cracked just a bit, and getting a little stronger lately. This last weekend I went about finding this pain in the nose. With a tip
    from a fellow Porsche nut I went directly to the 'fuel
    overflow expansion box'. This is a black 3/3/6 thermo-
    plastic box with two bungs on the bottom. The box lives behind the dash at about the location of the left gauge cluster, OR looking the other way, behind
    the fresh air duct on the fuel side of the car. Low and
    behold the box had sight cracks on the top and along
    the tops seam. When covering one bung and blowing into the other with the box submerged in water bubbles appeared at these suspect areas. The box can be ordered
    from Porsche (it stuck around till the end of the SC's) ... mine was not too bad so I 'welded' or remelted the bad areas back up with a soldering iron
    then sealed them up with black weather strip adhesive
    (almost NOTHING sticks to thermo-plastic) While I was
    at it I also rehosed the complete overflow system. After a 'up to the top' fill up and a 'brisk' ride
    through the hills, I have to say, this the first time
    the old blue car has been COMPLETELY 'smelless' .....

    For what it's worth .... Happy 'S-ing
    Chuck Miller

  2. #2
    GREAT TIP Chuck. I had one of the hoses come loose from the bung once. Ended up with a gas soaked sock, when gas ran into the passenger compartment. Sure glad neither of us was smoking...could have been Ka-Boom. I check the tightness of the hose clamps from time to time, try to not fill up allll the way when I buy gas.

  3. #3

    Gas Box

    Yep... I had the same problem. Talked to a guy at a swap this weekend with the same problem. Good tip on the soldering iron. I tried to epoxy mine and it worked for aaboouut 20 minutes! I replaced it at a cost of about $30.00 and no probs since. Wish I had known about the hot poker trick before.

    David & the Gang

  4. #4

    Re: Gas Box

    some months ago, I was in a local independent automotive shop. The owner was making a custom shaped fan shroud by cutting down a used shroud and welding the pieces together with a product I'd never seen before. This morning, I called, asked what the stuff was. It's simply called "Structural adhesive". It's a 2 part compound, comes in one of the 2 sided syringe type applicators. Steve (The mechanic) says it comes in various formulas, depending on the use of the thermoplastic being welded. There is a formula designed to be in contact with fuels. It's sort of expensive, $20 or so. He buys it through a local auto parts store. He told me you won't find this material at the huge discount automotive places like Kragen, Shucks, etc. However, this stuff does glue & seal thermoplastics. Steve tells me he's repaired plastic gas tanks with it. Should my gas box ever crack, I'll sure give it a try. So, if the hot poker fails...perhaps another alternative.

  5. #5
    Chuck Miller

    Fuel Smell

    Thanks for the tip Pwd72s .... That's what this forum

  6. #6
    Thanks for the compliment. BTW, reason I used the term "welded", though this is a cold application method, is that the structural adhesive stuff actually becomes part of the thermoplastic with it's (chemical?) reaction to the part being repaired. It's not simply a glue. Look at it kind of like a welding rod...for thermoplastics. Steve (the mechanic) is a big and strong guy. I noticed he was straining to push the material through the syringe...must be really thick material. Don't know if it comes in colors or not. Steve was using black, pretty close in color to our gas boxes. So guys, once again, don't knock the people who work with Detroit iron...they can teach you things...the custom fan shroud was for his wife's little s-10 chev. Blazer...seems Steve thought it needed a bit more power, so it's now running an LT1 engine. Power now "adequate", according to Steve.

  7. #7
    Hey guys, don't ignore this fuel smell problem! The answer is indeed in the fuel box or old lines and it's worth checking whether you have the odor or not.

    One night returning from dinner, we stopped to fill up and noticed the usual strong smell on the short ride home. Pulling into the driveway, the speaker wiring on the right side chose that moment to short against the body and larger sparks shot out from under the dash. Relieved at no explosion, we stared at each other in disbelief and I repaired the wire and the hoses before I could sleep that night!

    A word to the wise.


  8. #8


    Hi Guys,

    Chuck and I have discussed this before and the welding idea is well worth the saving of $30.00 from Porsche. MY problem is that I have replaced mine with a new factory unit about 2 years ago and now the smell is back. I will check it over the weekend using Chucks "bubble test" and if it in fact is the unit again, I will try one of the advised fixes. Thanks for the info. I also had the gasket under the fuel gauge sending unit fail. After replacing that gasket and retightening the unit...presto! No least for a while.

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