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Thread: CJ3A Direct Short Battery to Block: Ignition Issues

  1. #11
    Super Moderator bmorgil's Avatar
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    Chris the coil body is grounded at the engine block. It is probably the blue coating providing the insulator to ground. I was trying to be sure the engine is well grounded. Just to be sure check from the distributor housing casting to the Neg battery terminal, there should be 0 ohms. The distributor has to be grounded. Since the starter is turning over, I expect it is OK. Next check the coil wire for impedance. The coil wire should be around 5,000 to 10,000 ohms per foot if it is a resistor core wire. It will be much less if the wires are spiral core.

    If it passes the above I can currently think of only one more thing. Pull the distributor cap off and verify that the rotor is turning when the motor is spinning.
    Last edited by bmorgil; 04-29-2023 at 04:10 PM.

  2. #12
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    The distributor housing has continuity to the negative pole of the battery and the coil wire (appx 1ft) is at 6600 ohms. The rotor is turning.

    Should the coil housing be grounded to the block? As you indicated, it is not. Do you think it should be?

  3. #13
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    I need to thank you again for your help. I'm just out of ideas and appreciate any thoughts you have.

  4. #14
    Super Moderator bmorgil's Avatar
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    You are welcome, this is a bit baffling.

    It is possible the coil needs to have the housing grounded, usually it is not necessary.The distributor housing must be grounded. If the block is grounded, the distributor housing had also better show 0 ohms read on a very sensitive scale. The ground from the block to the battery must be large and a very good connection. If the ground is poor, when you hit the start, the current draw will be through other places as well as the poor connection. If it draws the smallest amount of ground current through the ignition module, it will ruin it. The distributor housing to the neg terminal of the battery needs to read 0 (Zero) Ohms.
    Last edited by bmorgil; 04-30-2023 at 05:05 PM.

  5. #15
    Super Moderator LarrBeard's Avatar
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    For what it's worth, I concur.

    The coil ground connections are returned through the (-) terminal of the coil - down through the points or electronic switch that does the point function - to chassis (engine block) ground.

  6. #16
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    Good Morning,

    And again, thanks for your each of your thoughts. I've inspected and cleaned up all of my ground strap connections (neg to body and block)...they all looked solid and oxidation free to start with. My resistance from distributor housing to battery negative reads .1 ohms on my most sensitive scale (200K Ohms).

  7. #17
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    I just ran a jumper from battery negative to the distributor housing and attempted to start....no spark.

  8. #18
    Super Moderator bmorgil's Avatar
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    Chris, we have covered it all. You must have a rash of bad distributor ignition modules. Do you have the original distributor around? The only other components that are left would be the Rotor and the Cap. Make sure the Rotor hasn't found a path to ground.
    Last edited by bmorgil; 05-01-2023 at 08:00 PM.

  9. #19
    Super Moderator LarrBeard's Avatar
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    "... .1 ohms on my most sensitive scale (200K Ohms)...."


    In this measurement, the most sensitive scale to check a really low resistance would be the R x 1 or R x 10 scale. What do you measure from distributor (-) to battery negative?

  10. #20
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    I measure .1 ohms when I touch the probes of my ohmmeter together. I get .1 ohms from my distributor to battery neg. 200K is my most sensitive setting. My wife would probably agree....I'm not sensitive enough:-)

    I do have the old distributor. I've never had the jeep running with that. I think new points and condenser would be in order. I've never set gap on point. I'll need to research that.

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