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When plug extenders go bad

Discussion in 'Technical Q&A' started by 4Webers, Jan 6, 2006.

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  1. 4Webers

    4Webers Formula Junior

    Nov 12, 2003
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    Darrell
    #1 4Webers, Jan 6, 2006
    Last edited by a moderator: Sep 7, 2017
    There are lots of threads in the archives about plug extenders failing, but I didn't find any pictures of one, so here ya go. It's hard to get a good picture of something this black, but you can see the hairline 'crack' on the bottom edge from straight up to about 4 o'clock. This extender is less than 2 years old, so don't discount the extenders as a potential source of your misfire just because they are new.
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  2. ernie

    ernie Two Time F1 World Champ
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    #2 ernie, Jan 7, 2006
    I'ma lookin anda starin, but I'ma nota seein.
     
  3. CliffBeer

    CliffBeer Formula 3

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    #3 CliffBeer, Jan 7, 2006
    In my experience, typically the extender goes "bad" not by way of a crack or something similar, rather, when a hole has been burned through the side of the extender by virtue of arcing of the spark to the head/cam cover rather than delivering the charge down through the plug. Most commonly this happens right where the extender wall gets close to the retainer spring for the top of the plug.
     
  4. Philjay50

    Philjay50 Formula Junior

    Jan 16, 2003
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    #4 Philjay50, Jan 7, 2006
    Mine had a hole burnt through it, I will post a piccy if I can find the offending bit.
     
  5. DGS

    DGS Seven Time F1 World Champ
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    #5 DGS, Jan 7, 2006
    Another question would be what causes burn-through to happen?

    Is it the result of bad vacuum advance? Mushy spark (old coil)? Mis-set timing?

    Or does it "jes happen"?

    Are some cars more prone to it than others, even within the same model?
     
  6. Dave328

    Dave328 Formula 3

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    #6 Dave328, Jan 7, 2006
    Just an DIY FYI:
    I keep a J-B Weld kit in my tool kit, just in case I'm in the middle of a drive and get that sudden dreaded miss. A quick road side coating of J-B Weld on the offending extender will solve it right quick. Heck, I haven't even gotten around to replacing the two I "fixed" 2 years ago because they are still working miss-free!

    Dave
     
  7. Jerrari

    Jerrari F1 Veteran

    Jul 24, 2001
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    #7 Jerrari, Jan 7, 2006
    Would an extender have to have a hole or crack in it to be bad? Could it look perfectly good and still be bad?
     
  8. 4Webers

    4Webers Formula Junior

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    #8 4Webers, Jan 7, 2006
    Last edited by a moderator: Sep 7, 2017
    This should help - I should have done this to the pic the first time...

    I missed diagnosing this extender as bad for a long time, because I was looking for an arc-through in the side, up near the plug connection, not down at the bottom. Also I kept thinking that the bad area was just a casting glitch or something. I expect that there is some sort of manufacturing void in this one that allowed the spark to go through it.
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  9. J.P.Sarti

    J.P.Sarti Guest

    May 23, 2005
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    #9 J.P.Sarti, Jan 7, 2006
    The end of the the extender cracking has no realtion to failure, its just a ceramic cover, take an extender apart and you will see a long piece of carbon and a spring like in a distributor cap, thats what fails and the burn though causing arcing or shorting in the tube walls.

    On my Bb I replaced the poor quality factory wiring set up, you have a lot of potential failure spots as well such as the clamp on the wire that attaches to the extender can corrode etc, I replaced the entire wire set with a Beru extender Porsche type set up that screw on the wires, cost less than 12 extenders for everything and is much more reliable.
     
  10. PAP 348

    PAP 348 Ten Time F1 World Champ
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    #10 PAP 348, Jan 7, 2006
    Yeah man,it may look like there is nothing wrong with the extender tube,but if you are unlucky enough,the carbon wire will be broken somewhere in the tube,which you cant see of course and it will cause a miss. But a simple spark test on the offending lead will tell you which is not sparking or not! ;)
     
  11. 4Webers

    4Webers Formula Junior

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    #11 4Webers, Jan 8, 2006
    J.P. - That isn't a crack, it's where the 20,000+ volts were leaving the inside of the extender and shorting to the head. As I said, it just looked like a crack and fooled me into not testing the extender. BTW, it checks out just fine with an ohm-meter. To further fool me, it wouldn't start shorting until it got warm, after the engine had been running for 5-10 minutes. Of course I blamed the poor carb...
     
  12. pcelenta

    pcelenta Karting

    Nov 1, 2003
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    #12 pcelenta, Jan 9, 2006
    darrell,
    are your extenders the aftermarket ones that Rutlands and the others sell? I replaced all of my originals (beru? or maybe some other name) with the aftermarkets and I will see the castings/mouldings on the aftermarket extenders are terrible compared to the originals. I too am having a problems with one in Cylinder number 3 and have order a replacement mine are about 2 years old also...it has no burn through the casting/moulding in particular around the bottom is kinda rough like yours...wonder if they are from the same batch.

    Regards,
    Paul
     
  13. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    #13 Dr Tommy Cosgrove, Jan 9, 2006
    I had one with a little hole burned in the side. If I remember the tiny hole had a white ring around it too. I think thst's how I spotted it. That was a few years back, though.
     
  14. Mike C

    Mike C F1 Veteran
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    #14 Mike C, Jan 9, 2006
    Actually, even wrapping it in electrical tape will serve as a temporary fix. I helped a buddy with that at Indy.
     
  15. 4Webers

    4Webers Formula Junior

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    #15 4Webers, Jan 9, 2006
    Paul, they were the $5 specials from Sodacoms, I got them 2 years ago. Definitely not the original brand with the logo on them. Luckily I kept my originals and found one that was still good enough to clean up and use. My bad one was in cylinder #3 also, hmmm...
     
  16. Verell

    Verell F1 Veteran
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    #16 Verell, Jan 10, 2006

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