Intermittent Loss of Spark/Backfire
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Intermittent Loss of Spark/Backfire

  1. #1
    Wet
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    Default Intermittent Loss of Spark/Backfire

    468, 871 blower motor. MSD 6al
    The last couple of times out when the engine was cold, it ran just fine as always. Ride out to the sandbar, spend a little time there, fire it up, and backfire through the carbs. Hmm. Well, I have to drive it back to the ramp. As we drive, the spark would come and go on one (don't know which) cylinder. A few minutes later, it would clear up and I could run it like I normally do. The backfire comes in the turning over, the spark loss comes as we are running. Does this sound like plug wires going bad? I'm thinking it's an errant spark, or arcing wires causing the backfire. Anyone?

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    plug wires are awhole lot cheaper than wipeing out a motor!! ...get a new set ...also...carbs backfireing on start-up sounds like a timeing issue!
    re-check your timeing ...just sayin' my .02 cents

    FastRat

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    Wet
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    Definitely getting plug wires, but I'm wondering if I should be looking elsewhere?

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    Senior Member Widetrack's Avatar
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    Check the cap! I had one that drove me nuts trying to figure out what was going on! Look for carbon tracking and look at the button too! My.02 WT


    SOMEONE SAID YOU CAN'T TAKE IT WITH YOU! SO,IM BURNING IT UP ONE GALLON AT A TIME!
    WT

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    Senior Member GA Jet's Avatar
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    Quote Originally Posted by Widetrack View Post
    Check the cap! I had one that drove me nuts trying to figure out what was going on! Look for carbon tracking and look at the button too! My.02 WT
    x2

    Mine was backfiring through the carb, timing wouldnt set, wouldnt stay running. Long story short I had to replace the whole distributor on my 455 but it worked like a charm!

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    Senior Member cave's Avatar
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    When my MSD 6al box was ready to take a dump it did the same thing your saying happened to you. I sent it to MSD and they fixed it. Got to go to MSD site and get an number and then send it to MSD. It was like 50 bux to have them fix the box and ship it back.

    It could be the wires too. Wasnt for me. I replaced every thing sept the box. Dizzy too. Ended up with an all new system and a back up everything
    Takin it home

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    Quote Originally Posted by Wet View Post
    468, 871 blower motor. MSD 6al
    The last couple of times out when the engine was cold, it ran just fine as always. Ride out to the sandbar, spend a little time there, fire it up, and backfire through the carbs. Hmm. Well, I have to drive it back to the ramp. As we drive, the spark would come and go on one (don't know which) cylinder. A few minutes later, it would clear up and I could run it like I normally do. The backfire comes in the turning over, the spark loss comes as we are running. Does this sound like plug wires going bad? I'm thinking it's an errant spark, or arcing wires causing the backfire. Anyone?
    i have an msd 6al in my blown drag car and it has some type of missfire at 2900 to 3000 rpm's , i found this out when box was in my street rod. it misses and car would be bucking back and forth , changed everything plugs , wires , distributor , made sure had correct voltage to box ect. switched box with my spare from my jet boat and now runs perfect , but reinstalled in drag car because it never hardly ever see's below 7800 . but like clock work it still misses 5 years later , and msd told me either they work or they dont period . thats a bs statement cause mine does have a miss , almost like randomly shuts off several cylinders with no back firing. i would also pull blower and check base gasket or if you have street manifold with pop -it style resettable blow off valve gasket . vacuum leaks are most likely the culprit , also check belt tension if to tight and blower expandes . which they all do , they belt may get to tight and lift the back of the blower upoff the manifold
    "Ill be your huckleberry"

  9. #8
    B&G
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    Call MSD with your ignition components accessible, they can walk you through some quick tests, Maybe you'll stumble on to something. Magnetic pickup in distributor, 6AL Box, ETC. Also we had problems with cap and rotors for a few months about a couple years ago. Maybe a bad batch?
    Last edited by B&G; 09-09-2010 at 06:37 PM.

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    Wet
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    I pulled the rev limiter chip and had no more issues. This is the second MSD that this has happened to.

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    Senior Member miketeast's Avatar
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    Quote Originally Posted by Wet View Post
    I pulled the rev limiter chip and had no more issues. This is the second MSD that this has happened to.
    advanced electronics
    Team FTL
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