Topic: Early 36 flathead, rebuilt coil, no spark


Buckd44    -- 11-08-2015 @ 1:03 PM
  I had a problem with not all cylinders getting spark. New caps, wires and a rebuilt coil, everything ran great for about 5 miles. Then nothing. No spark at any cylinders. Engine turns over though. Sounds like a bad connection somewhere but have no idea?
Thoughts?
Thanks,
Nate


carcrazy    -- 11-08-2015 @ 4:44 PM
  I would check all of the connections first. The connections between the coil and the rotor could have opened up with engine heat. If you have a spare condenser, install it to see if it cures the problem. If still no luck, the coil has probably gone bad.


MG    -- 11-08-2015 @ 4:52 PM
  Do you have voltage to the input/primary winding of the coil? Check for loose connections....


Buckd44    -- 11-08-2015 @ 5:34 PM
  The whOle distributor, coil and all was sent down to Florida to be gone over and the coil was rebuilt. Rebuilt coil is bad after 5 miles?


MG    -- 11-08-2015 @ 5:45 PM
  Maybe you've got an intermittent on/off ignition switch. Again, check for voltage on the input side of the coil with the ignition switch ON....


Buckd44    -- 11-09-2015 @ 5:43 PM
  I found this (picture attached) by passed that with new wire. I have 2.2 volts at the coil. I had 6.8 all the way till the block on the firewall, other side of it is 2.2. I assume this is some sort of resister. (My electrical knowledge is poor.)


MG    -- 11-09-2015 @ 7:27 PM
  You should have another volt plus the 2.2 volts at the coil. I hope you eliminated that frayed wire at the ammeter. There should be no direct electrical contact there. The ammeter works by induction from the insulated wire that passes through the 'loops' on the back side of the ammeter. I hope that the rest of the wires in your car are not in the same condition as seen in the picture you posted....


Buckd44    -- 11-09-2015 @ 7:39 PM
  Yes, I bypassed the amp meter. So what is my next step? You're saying I should have 3.2 volts at the coil? Assuming the resister is bad? Why else would I be losing that volt?
Thanks.


MG    -- 11-09-2015 @ 7:55 PM
  Yes. The maximum voltage for original type Ford coils is 3.5 volts with the points closed. If you are measuring just 2.2 volts at the coil side of the resistor, the resistor is suspect. Maybe the resistor is going 'open' on you when it heats up. This would explain why "everything ran great for about 5 miles." If the resistor is going 'open' the engine won't fire. Resistance increases with heat and those resistors do get very hot....

Have you tried to start the car since you bypassed the ammeter wire?

This message was edited by MG on 11-9-15 @ 8:02 PM


Buckd44    -- 11-15-2015 @ 3:12 PM
  New resistor, 3.5 volts at the coil. Still, no spark anywhere.


MG    -- 11-15-2015 @ 3:29 PM
  Given what you've said, I suspect there is no good contact from your coil through its carbon 'brush' contact to the rotor in your distributor.... Many times, when the coil is mounted/installed onto the distributor, the carbon brush will fall out of the coil or become wedged. This especially, if you mounted the coil onto the already mounted/installed distributor on your engine....
Inspect this by removing the left and right cover/contact plates from the distributor and and look/see if the carbon brush from the coil is in contact with the rotor...

This message was edited by MG on 11-15-15 @ 3:41 PM


Buckd44    -- 11-15-2015 @ 5:20 PM
  It's still there. I am able to get a flathead inbetween the rotor and the carbon nipple and it springs back to make contact. Attached is a picture.
Thanks for the insight, this is somewhat new to me.
Nate


MG    -- 11-15-2015 @ 6:05 PM
  Damn, I wish I were there with you to help you troubleshoot this! That you are measuring 3.5 volts at the input to the coil with the ignition switch 'ON' means that the ignition switch to the coil circuit is good! Given this, with a known good coil, you should have 'spark' to the plugs when the starter motor is turning the engine and distributor over. WTF! Where's the air gap??? I find it hard to believe that your starter motor is drawing sooo much current away from your ignition circuit that you don't have spark. Is your distributor turning over when trying to start the engine??? If so, I can only surmise that you have an intermittent open in the ignition circuit when trying to start/fire the engine, Again, I wish I were there....


TomO    -- 11-16-2015 @ 8:10 AM
  Does the rotor turn when you crank the engine?

Does the voltage vary at the input to the coil when you crank the engine?

Tom


Buckd44    -- 11-19-2015 @ 8:30 AM
  After no luck, I tore the distributor off, after careful inspection, one of the points has a crack in it and isn't releasing. Sending it back out to get fixed.


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