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Arcing light show on my exhaust manifolds. Update-Very strange!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by coyle13, Feb 23, 2004.

  1. coyle13

    coyle13 Registered Member

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    Well,
    I was setting the timing a few nights ago and I noticed a unmistakable snapping sound, so I turned out all the lights and noticed an electric light parade marching across my intake manifold and jumping from all the spark plug wires to the exhaust manifold. I knew the distributor had a lot of play in the shaft and the coil was testing marginal, so I decided to just get a new (rebuilt) distributor and put in the MSD coil and brand new wires that had been sitting in the garage for the past 6 months, waiting to be installed. Anyway, I replaced the distributor with new pickup and module, cap and rotor (Accel), AC Delco plugs gapped at .40, MSD wires and Blaster coil. I used a MSD wiring harness for the GM dual connector coil with good crimp connectors and wrapped all the connections with self-vulcanizing electrical tape.
    Long story short, the light show is EXACTLY the same, only it is much brighter now because of the MSD. The strange thing is that I replaced EVERTHING except the original GM harness connections. The one from the coil to the distributor module ohmed at 0, but I don't know how to test the power lead going to the coil from the factory harness. Obviously, I have a bad ground or short somewhere, but how do I go about the diagnostic on this? I know the juice will follow the path of least resistance, but I have never seen so many different spark "leaks" at different places at once.


    UPDATE:
    I decided to isolate the coil to see if the arcing would stop. So, I attached the coil with some nylon spacers and wood screws to a small piece of 1/2" plywood and attached that to the firewall above the distributor, effectively insulating the coil from any metal contact. No more arcing on the intake manifold, but ALL the plug wires were still arcing like crazy. So, I ohmed one of the brand new MSD wires (#8) and it was bad. (It showed infinate resistance). So, I replaced that wire with a Taylor Spiro-Pro that I had as a spare. It is about 2.5 feet long and ohmed at 643. Good wire. Just for good measure, I replaced the spark plug with a brand new AC Delco gapped at .37 (even though I just replaced that plug 1 week ago.)
    I fired it up and, of course, it was arcing like crazy on the #8 wire. I pulled the #4 wire and did the same proceedure with a good wire and a new plug and the same thing. Arcing like crazy. So, I did #6 and #2 with known good wires (674 and 642 ohms) and brand new AC Delco's gapped at .37. Still the light show.I replaced all the brand new stuff I put on one week ago with NEW brand new stuff that tested good and it still arced like crazy. In one week, my brand new MSD wires were all fried. The idle is hunting and surging, but the truck runs pretty good. Power is fine and mostly smooth. WTF? /forums/images/graemlins/angryfire.gif
    It seems that the secondary ignition is firing a little hot and if frying everything in a hurry. What would cause this? I can effectively rule out the cap/rotor/module/pickup/wires and plugs. What else? Would the ESC cause this type of problem? A bad ECM ground? I am at a loss. ANY help or suggestions would be apprreciated.
     
  2. NerdBoy

    NerdBoy 1/2 ton status

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    Re: Arcing light show on my intake manifold. Need help!

    This is a long shot, but what is your engine ground connected to, and what is the part the ground is connected to, connected to?
    And, in what shape is the ground strap?
    If the ground is connected to the manifold, and there is anti-seize on the manifold bolts, your plugs might not be grounding well. Check all the grounds in your system.
     
  3. coyle13

    coyle13 Registered Member

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    Re: Arcing light show on my intake manifold. Need help!

    I did just replace the intake manifold gasket (again, because the one I replaced 6 months ago still leaked) and I used a bunch of thread sealant on all the intake bolts. The grounding strap does go to one of the intake manifold studs. So, I will run some jumper cables from known good grounds to the neg. battery terminal and see if that helps. Thanks for the info.
     
  4. JP's K5

    JP's K5 Registered Member

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    Re: Arcing light show on my intake manifold. Need help!

    Did you change the plug wires along with the rest of it? My pickup used to look like the 4th of July when the wires went bad. If you replace them make sure they arent touching each other or the manifolds. Also invest in some nice wires. Taylor hasnt done me wrong yet(8mm). /forums/images/graemlins/thumb.gif
     
  5. NerdBoy

    NerdBoy 1/2 ton status

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    Re: Arcing light show on my intake manifold. Need help!

    Let me know if that fixes the problem...
     
  6. coyle13

    coyle13 Registered Member

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    Re: Arcing light show on my intake manifold. Need help!

    I put a new set of MSD wires, which replaced an older set of Taylor's, which were probably fine. Oh well, I have a set of trail spares /forums/images/graemlins/thumb.gif Also, everything is routed carefully and separated. No wires are cross-firing. I just have a wicked ignition "leak". If I have a bad ground, will it cause the spark "leak" that I have or is it more likely a bare live wire somewhere?
     
  7. NerdBoy

    NerdBoy 1/2 ton status

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    Re: Arcing light show on my intake manifold. Need help!

    If you isolated your manifold by putting sealant on the bolts, and the ground goes to the manifold, it may be the only good ground on the engine. Electricity tends to take the path of least resistance. If the path through the spark plugs (and the gap) to the heads, and then through the sealed bolts on the manifold, to the ground strap is higer resistance than just jumping through the insulation to the mainfold, then that is the path it will take. Spark plug wire insulation is good, but it can break down quite quickly when the spark plugs aren't in a well-grounded engine.

    By the way, the ground cable from your battery should go straight to the engine block. The when I was having ignition problems with my MSD 6AL, the technician told me to fix that before we went any further diagnosing it.
     
  8. coyle13

    coyle13 Registered Member

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    Re: Arcing light show on my intake manifold. Need help!

    Thanks for the info. Just a couple more questions: Should I test for a bad ground by running a jumper cable/alligator clip from the ground in question to the negative battery terminal and see if it goes away or should I just run some 4 gauge grounding straps from the engine block to the battery and from the frame to the battery and from the block to the frame and see if that makes it go away? Also, when I replaced the intake manifold gasket, there were 2 grounds attached to the rear of the passenger side head that were completely stripped of insulation and oil soaked> I re-crimped them and taped them well. There was also a 10 gauge flat copper grounding strap that went from the head to the passenger side firewall. Should I move these to a block ground or should I just add the new grounding straps and leave the existing ones where they are? Thanks again for the help. /forums/images/graemlins/cool.gif
     
  9. NerdBoy

    NerdBoy 1/2 ton status

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    Re: Arcing light show on my intake manifold. Need help!

    I would just relocate the main ground that comes from the battery to the block. Possibly to a mounting bolt for one of your accessories (A/C, Power Steering, and such) The rest of the ground straps sound like they are in good locations. As long as there is a good strap from the engine (block or head).
     
  10. coyle13

    coyle13 Registered Member

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    Re: Arcing light show on my intake manifold. Still need help!!

    Well,
    I relocated the main grounding strap to the front of the engine block and I still have the light show. Didn't reduce it a bit. Anyone else have any ideas? Also, I did take the truck to a mechanic a few weeks ago to do a diagnosis for a vacuum leak. He put the truck on the "machine" and gave me a print-out showing the condition of the major systems. The primary and secondary ignition systems were o.k. Does anyone know where I can get an engine wiring schematic for a '91 Blazer?
    Thanks for your help!
     
  11. coyle13

    coyle13 Registered Member

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    Re: Arcing light show on my intake manifold. Still need help!!

    Updated-to the top
     

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