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This is a head scratcher for sure.! Keep us posted and good luck.;)
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Since you have the distributor out of the car, use your VOM to check the connectivity between each terminal on the cap, and the center terminal of the cap, as you turn the gear with your fingers (and thus rotate the rotor). If you only get connectivity with terminals 2 and 6, then there's your answer. If you get connectivity on all eight, then I would suspect the distributor was not installed properly and cylinders 2 and 6 were just the "lucky" ones that had a spark come at kind of the right time.
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Ok Patrick, What am I measuring for connectivity. There are two wires that come off of the distributor. When I rotate it what should I be measuring? What point to what point?
Phil |
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Now, put one lead on the coil terminal that is in the middle of the distributor cap. Put the other lead on any of the other eight terminals that surround the circumference of the cap. Then rotate the gear at the bottom of the distributor so the rotor revolves under the cap. If all of a sudden the needle swings showing you have a good connection, move to the next terminal and do the same thing. I'm just trying to determine whether there is a faulty connection for all the terminals on the cap except #2 and #6. Make sense? |
I got no connection on any of them. I held one lead on the coil terminal and went around all of the cylinders. No connectivity whatsoever on any of them.
Phil |
Is that telling me the magnetic pickup is bad?
Phil |
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Even if there was just the tiniest gap between the rotor tip and the terminals, that would be jumped easily by high voltage, but not register as connected with a VOM, I would think the rotor tip would touch at least some of the terminals as you rotate the gear. Any chance the rotor prong is not touching the iron ball?
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I tried bending that upward and made no difference. I tried different scales and a different rotor button. I think the gap between the rotor button and the cap is a significant gap that is jumped when there is power to it. That would be the reason for infinity on resistance (i.e. They never touch).
Phil |
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I would say try a brand new cap......
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That I can do. Just seems odd it worked last weekend but not this. Maybe taking it on and off many times had an effect. I will talk to MSD first and then figure what to do. The distributor worked fine and the car ran fine even after the hi rev. Something isn't right and it is driving me bonkers. Seems that it should be much simpler..
Phil |
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EVERY distributor has a tiny airgap between the rotor tip and the spark plug terminal. |
Sit the cap on the rotor button, you should feel the spring loaded contact of the carbon brush.
If the cap just sits there on it's own, there is no contact at the rotor centre contact with the carbon brush. Sounds like a mismatched cap and rotor button. |
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You are correct. There has to be small gap for the spark to arc from the rotor tip to the individual spark plug lead. But PatrickT knows this!!;);) |
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Many folks carry an extra new MSD cap in their trunk just because of this kind of problem.
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In a perfect world they would touch, but it would be noisy until the contacts wore each other out to zero clearance.
Some rotor buttons have adjustable tips for those who like to set minimum gap. If you can get .001 across all terminals, you are doing well. I think the OP is chasing a component fault. Either weak coil, bad pickup, or bad module, or possibly bad wiring installation. Myself, I would chuck all the MSD stuff out, start fresh with Mallory or Pertronix. |
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