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Thread: Help with BBC mechanical fuel pump

  1. #1
    Vintage Eliminator 21
    Put a new Holley mechanical pump in my BBC last weekend. When I took it to test, it leaked at the fuel line connections on the pump.
    Did a redo on the teflon tape Monday night and tightened as much as I dare (did not want to crack the aluminum pump housing). Tested again this morning and still had a slight leak on the output side. Tightened and seemed to leak more.
    I've posted photos of what it looks like now.
    Any ideas or suggestions would be appreciated.
    http://img.photobucket.com/albums/v4...BCfuelpump.jpg
    http://img.photobucket.com/albums/v4...Cfuelpump2.jpg

  2. #2
    flat broke
    For one, teflon tape on fuel lines can be a problem waiting to happen. You'll notice that the tape is frayed looking on the outside of the inlet plumbing in your pic. You can imagine that those frayed ends could let go and fall off into the bilge right? Well, they can also fray on the end inside the pump from being cut in the threads. If that happens it can get inside the pump or line and be passed into the carb if there is no filter between the pump and carbs. From there they can do anything from sticking a needle and seat to clogging a main jet. So from that standpoint, you might want to look into using teflon paste or some Permatex 1B on your fittings in place of the teflon tape.
    As for why yours is leaking... It might not be tight enough, or perhaps the fittings you have may not have a good enough taper to seal properly. It's hard to tell from a picture. Assuming the pump is new and the threads were in good shape, you've already checked for cracks in the housing and all is well, I'd change to teflon paste or Permatex 1B and use a little more torque. if that fails, change out the fittings, again using teflon paste of Permatex 1B.
    Good luck,
    Chris

  3. #3
    Saab
    Make sure you have the right fitting, I believe that takes a flare fitting so the threads dont seal it, the inner flare does. I think. take a look and see

  4. #4
    76ANTHONY
    For one, teflon tape on fuel lines can be a problem waiting to happen. You'll notice that the tape is frayed looking on the outside of the inlet plumbing in your pic. You can imagine that those frayed ends could let go and fall off into the bilge right? Well, they can also fray on the end inside the pump from being cut in the threads. If that happens it can get inside the pump or line and be passed into the carb if there is no filter between the pump and carbs. From there they can do anything from sticking a needle and seat to clogging a main jet. So from that standpoint, you might want to look into using teflon paste or some Permatex 1B on your fittings in place of the teflon tape.
    As for why yours is leaking... It might not be tight enough, or perhaps the fittings you have may not have a good enough taper to seal properly. It's hard to tell from a picture. Assuming the pump is new and the threads were in good shape, you've already checked for cracks in the housing and all is well, I'd change to teflon paste or Permatex 1B and use a little more torque. if that fails, change out the fittings, again using teflon paste of Permatex 1B.
    Good luck,
    Chris
    when working with fuel i always use the paste, it helps out alot and seals better too. the fittings are sometimes manufactured really crappy, so i would try a aeroquip or something nice, it will get rid of the leak fo sho

  5. #5
    SmokinLowriderSS
    Make sure you have the right fitting, I believe that takes a flare fitting so the threads dont seal it, the inner flare does. I think. take a look and see
    Double-check you have the right fittings. My non-holley took std tapered pipe-thread fittings, yours may be different.
    You cannot get the wrong fittings to seal, no matter how much thread sealant you use. Flare thread is straight, pipe thread is cut with a taper.
    Then, if it's tapered pipe fittings, Rectorseal#7, usable on fuel, gas lines, water, even potable (drinking) water. I keep a small can arround.
    You can probably spend more $$$ on another product, but sealed is sealed.
    Hell, you could use a small ammount of it on flare threads as an anti-gall/sieze agent.
    Rectorseal #7 contains PTFE/Teflon.
    And it DOESN'T TAKE MUCH.

  6. #6
    DelawareDave
    Maybe it's the pic, but it looks like there is a crack in the casting, just to the right of the lower fitting, running horizontal. Or is it casting flash?

  7. #7
    atxwrangler
    i saw that,but,thought if that was a crack,surely he would have seen it!

  8. #8
    flat broke
    Maybe it's the pic, but it looks like there is a crack in the casting, just to the right of the lower fitting, running horizontal. Or is it casting flash?
    That looks like a parting line from the casting process, and he said it was leaking from the output which would be the top hole. But it never hurts to double check for cracks.
    Chris

  9. #9
    Senior Member
    Join Date
    Feb 2009
    Posts
    2,626
    As has already been stated, DO NOT use teflon tape on fuel line fittings. Teflon paste is fine.
    Second, to clarify what Saab said, you DO NOT use teflon tape or ANY type of sealant on flare fittings. They are designed to seal at the taper in the pipe to the taper inside the fitting. The threads do no sealing at all. If you are leaking at a flare fitting you need to dissassemble and inspect the contact pattern between the pipe and fitting. If the flare on the pipe was poorly made, you may need to replace the pipe. When tightening the pipe into the fitting, hold the fitting with one wrench and use a LINE WRENCH(also called a FLARE WRENCH) to turn the
    pipe nut. Using a regular wrench will distort the pipe nut and can prevent proper tightening. If the pipe you are using is new, it may take quite a bit of torque to pull it into place on the flare fitting.
    This pic makes it clear you have used tape in the flare fitting.
    http://img.photobucket.com/albums/v4...Cfuelpump2.jpg

  10. #10
    DelawareDave
    I, for one, am suspicous of the type of fittings he is using, as mentioned by Smokin'. There is tape on the line fitting, which is a flare, and requires no sealant. The fitting it is screwed into, looks to be near bottomed out in the next fitting, making me wonder what it is, and there is no tape/sealant visible there. Then, what is the fitting screwed into the pump itself? Male NPT, but what is the female side? And why are there 2 fittings at each connection? Using the proper reducers, if required, reduce the chance for a leak. And- which fitting is actually leaking? NPT into the pump body? Flare fitting? Or the one in between?
    Something just doesn't look right in the choice of fittings used.

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