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Technical Spark jumping hei

Discussion in 'The Hokey Ass Message Board' started by coolieman, Jun 25, 2020.

  1. coolieman
    Joined: Jan 31, 2010
    Posts: 111

    coolieman
    Member

    Spark started jumping from under coil cover to spark plug terminals misted some water and saw yellow arch on cap replaced cap and still doing same thing?? Thanks mike
     
  2. saltflats
    Joined: Aug 14, 2007
    Posts: 10,094

    saltflats
    Member
    from Missouri

    Is the coil grounded?
     
  3. onetrickpony
    Joined: Sep 21, 2010
    Posts: 427

    onetrickpony
    Member
    from Texas

    Missing the ground on the coil. It goes from one of the coil screws to the harness connection.
     
  4. coolieman
    Joined: Jan 31, 2010
    Posts: 111

    coolieman
    Member

    ground wire is connected
     
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  5. 52HardTop
    Joined: Jun 21, 2007
    Posts: 897

    52HardTop
    Member

    It may be a bad wire on the coil. I saw this on a Flathead one time. It turned out to be a bad coil wire that didn't look bad.
     
  6. I suspect a missing pathway for the spark to take the rotor path.
    Check to see if the rotor or cap has the center contact button missing or the metal contact strip on the rotor, or rotor tip damaged in any way.
    If the coil cant discharge thru the rotor or center button, it will be forced to arc across the coil or anything nearby.

    If the sparking is not nearly as fast as you would expect from a coil or rotor problem on all cylinders, and it seems to spark at a rate slower than an "all cylinder event", then I would look for a completely failed plug wire or plug.
    ..sometimes a cracked cap can act like that . Cracks aren't always easy to spot.

    WHY BE ORDINARY ?
     
    Last edited: Jun 25, 2020
  7. VANDENPLAS
    Joined: Dec 14, 2009
    Posts: 2,377

    VANDENPLAS
    Member

    It’s looking for a path of least resistance .
    Why?

    damaged/ corroded wiring
    Bad connection
    Rotor button
    Connector loose on the pins
    Something is not correct!
    Electricity takes lazy that way.
     
    partssaloon, Truck64 and flatford39 like this.
  8. sdluck
    Joined: Sep 19, 2006
    Posts: 2,426

    sdluck
    Member

    Bad spark plug wires
     
  9. Budget36
    Joined: Nov 29, 2014
    Posts: 3,467

    Budget36
    Member

    Is this a coil-in-cap HEI?
     
  10. Mr48chev
    Joined: Dec 28, 2007
    Posts: 26,946

    Mr48chev
    ALLIANCE MEMBER

    grease, oil , dirt, and moister will raise havoc too. Anything that can create a path for the electricity to take that has less resistance than it's designated path.
     
  11. Nicholas Coe
    Joined: Jul 5, 2017
    Posts: 1,456

    Nicholas Coe
    ALLIANCE MEMBER
    from Tontitown

    I have been dealing with a similar problem. We found that our coil to distributor wire was not functioning properly. It looked fine.

    Chasing this issue we replaced the coil, distributor, and spark plugs before suspecting the coil wire.

    Sent from my Pixel 3a XL using The H.A.M.B. mobile app
     
  12. coolieman
    Joined: Jan 31, 2010
    Posts: 111

    coolieman
    Member

    Yes it is hei coil in cap and spark is jumping under coil cover to spark plug boot
     
  13. onetrickpony
    Joined: Sep 21, 2010
    Posts: 427

    onetrickpony
    Member
    from Texas

    When the wires get bad on an HEI, they tend to burn a hole in the rotor and the spark grounds out there. Pull the rotor and look closely at the center area under where the coil connects, right above the distributor shaft. If you see a dark spot (white rotor) or a lighter gray spot (black rotor) developing, the wires could be bad.
    Another area that is often missed is the rubber washer under the coil. It is recommended to use some silicone grease on both sides when the coil is installed. This keeps the rubber from drying out and allowing moisture to collect under the coil. Moisture in that area can contribute to the spark jumping you are seeing.
    It has been my experience that once this starts happening, you get a carbon track on the cap even if there is no crack. The only way to stop it is the replace the cap and make sure you move the ground wire or strap to the new one and grease the rubber washer. Of course, you also have to change the plug wires if that was the cause of the problem or it is just going to start again in a few miles.
     
  14. Truck64
    Joined: Oct 18, 2015
    Posts: 4,056

    Truck64
    Member
    from Ioway

    An Ignition scope, by the way can save hours of head scratching and needless parts replacement and even better, actually discover the defect so it can be remedied. Solid state units from the 60s and 70s can often be found pretty cheap. High voltage is weird stuff, as mentioned it will always try to take the easier path to ground.
     
    Truckdoctor Andy likes this.
  15. coolieman
    Joined: Jan 31, 2010
    Posts: 111

    coolieman
    Member

    I replaced distributor cap also found 1 bad spark plug boot top of distributor tested coil and pick up I have Isolated the sparking sound to under the coil cover put 2 different coils in cap that tested good I am just sharing this last post to see if that would narrow it down for anyone Thanks for the replies ,Mike
     
  16. Truck64
    Joined: Oct 18, 2015
    Posts: 4,056

    Truck64
    Member
    from Ioway

    Right, I get that. I've done "troubleshooting" with the parts cannon myself a few times. It does work, sometimes. Just often enough to be reinforced.

    In the .mil we were sometimes basically ordered to do that, by someone who didn't actually have to do the work. This is when I started to pay more attention to actual diagnosis, instead of throwing parts around, because, while the parts weren't paid for by me, it would be my weekend ruined, not theirs. (Surprisingly or maybe not so surprisingly, publicly exposing people as dumb shits is not always without consequence)

    I'm just sayin'. A scope is some good shit for looking over the ignition system, even if every part is brand new. Maybe, especially if every part is brand new.
     
    Truckdoctor Andy likes this.
  17. saltflats
    Joined: Aug 14, 2007
    Posts: 10,094

    saltflats
    Member
    from Missouri

    20200626_135318.jpg
    Is it wired like this?
     
  18. coolieman
    Joined: Jan 31, 2010
    Posts: 111

    coolieman
    Member

    No it just has 1 black wire from coil body to medal frame around coil
    A picture is worth a thousand words !!! ,when my cap broke originally I just switched distributors and didn't realize I was missing ground connection, I gueess that why I was wondering how coil was grounding Thanks everyone for your time,Mike
    ,
     
  19. saltflats
    Joined: Aug 14, 2007
    Posts: 10,094

    saltflats
    Member
    from Missouri

    Some caps have a metal strap that fits under the coil and bends up and down to the center terminal as the black wire is in the picture.
     
  20. Atwater Mike
    Joined: May 31, 2002
    Posts: 10,092

    Atwater Mike
    ALLIANCE MEMBER

    A friend had this problem, I asked about the ground, he just said "Yeah, it's grounded.."
    Whole BOX LOAD of corrective parts later, he said, "Well...then take a look at it!"
    Regretful for 'annoying' him, I looked. Then made up a nice 16 gauge ground pigtail.
    His unduly replacement of non-warranted electrical parts precluded any thanks for such an uncanny fix. :p
     
    Truck64 likes this.
  21. Did I just see you sayin that yours did not have that black wire going from the coil transformer frame to the center terminal of the cap-coil connection?
    You MUST have a ground connection to the center terminal that also connects to the ign coil metal frame. that must be your missing path that is causing all the trouble.
    YOU MUST HAVE THE CENTER WIRE TERMINAL HOOKED UP TO THE COIL FRAME AS IN THE PICTURE. If it is missing, that's your problem.
    If that path is missing, the current will seek other improper paths.

    ....unless I misunderstood your description :)

    WHY BE ORDINARY ?
     
    Last edited: Jun 26, 2020
    Truck64 likes this.

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