1970 Ignition Problem

Electrical and Ignition

  1. Mark Robinson

    Mark Robinson New Member

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    1970 Road Runner runs great but after it gets hot I can crank it but it won't fire. I replaced the ballast and change the module to a 5 pin ( read somewhere that if you have 4 lead ballast you had to use a 5 pin module). It worked better but now after hot it starts, but if I let it sit for a minute it won't. Sometime when I jiggle the key while starting it will start and was going to replace the ignition switch next. But this problem has to be heat related - anyone run into this before? Driving me crazy...



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  2. Big John

    Big John Sit back, relax Don't bitch about the cigar smoke

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    I know this flies in the face of the "parts cannon" approach to repairs that most guys will give you, but here goes.

    Get out your digital multi meter and when this happens, with the key "on" check for voltage at the plus side of the coil primary. If no voltage, start checking back to the ballast resistor and back to the ignition switch from there.

    If you have voltage, key off, unplug the distributor and check resistance (ohms) between the two terminals on the distributor side. You should have 150-900 ohms resistance between those two connections. If you have more, the pickup is shot.

    You can check the coil by disconnecting the wires and checking resistance across the primary. You should have about .75 ohms resistance there. Check resistance from either primary terminal to the center and you should have 10,000 ohms resistance or so. Those are really generic readings... and not for specific coils... and it can be argued that it's not the best test in the world, so don't discount that it might still be the coil even if those two readings are OK.

    My money is on the distributor pick up or the coil.... That is assuming that this is an electrical problem and you checked and there was no spark.

    Whoever told you about the 5 pin/ 4 pin deal... Stop listening to any advice they give you.
     
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  3. 69hemibeep

    69hemibeep Sponge Bob Square Wheels

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    I suggest you start replacing one part at a time until it goes away :lol: Good advise Big
     
  4. Mark Robinson

    Mark Robinson New Member

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  5. Basketcase

    Basketcase Luddite

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    listen to Big...he knows his chit
     
  6. Mark Robinson

    Mark Robinson New Member

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    IMG_2665.JPG Thanks John. Got out my meter and it 'a shot. Opened distributor and check out pickup - was going to take it out and get a new one but it wouldn't come out (need to study that one). I did notice that the wire coming from the distributor was pinched between the distributor and hot water hose. Pulled the wire to look at it - looked ok - reinstalled it and now it won't start at all. Think I'm getting closer to the problem. Will let you know what happens.
     
  7. Russ69Runner

    Russ69Runner Well-Known Member

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    Could be a broken wire where it was pinched. Big is the man. Have had bad coils in past motor would run grate and just shut down like you turned off the gas. Other ones would crank the motor shut it off then would not start. The Ignition coil can drive a man nut's. So test it like john said if it reads bump it or shake it to see if it has an internal bad connection. From now on I just get a good one and replace it. Oh I would clean that firing cam the points look dirty to me with some emery cloth. Might help make better contact. Russ.
     
  8. Mark Robinson

    Mark Robinson New Member

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    Thanks for your thoughts Russ. Progress for the other day. Talked to my son and told him I thought I had the problem licked/identified and we should focus on the pinched wire idea. He looked at it and found that I forgot to plug in the distributor connector. I felt so stupid especially after telling you all how smart I was. The car started right up - the good news is that the problem has gone away for now. It will be back. Russ, the first thing I did was replace the coil (forgot to mention that). I'll clean up the cam like you suggested. I put this car up for sale the other day, but today I was reading about the 392 Hemi conversion - that sounds like fun. And maybe my distributor problem will go away. Anyone out there need a 383 - runs great??
     
  9. Russ69Runner

    Russ69Runner Well-Known Member

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    Yep. That is what kid's are for. Good luck with the Hemi with new motor should have fun. :lol:
     

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