Intermittent spark

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Craig Burriss

Craig Burriss

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I just got my alternator back for my 70 Duster today. Bolted it on and fired the car up. The 440 started right up just like it always has.
It’s got a Summit brand electronic distributor and a blue 4 pin ECU and a two post ballast resistor that came with my MSD blaster coil.
I was about to start setting the timing with my new timing light and as soon as I turned the distributor probably 1°, the car shuts off. I get it started back and it’s running rougher than normal so I put the distributor back EXACTLY where it was to begin with. The car dies and won’t start back. I checked all of the wires to see if I somehow unplugged something but nothing was wrong.
The car is getting plenty of fuel so I know it’s not that. My timing light was also not flashing or showing the rpm like there was no spark flowing through the #1 spark plug wire.
Because I didn’t want to keep cranking the engine trying to find spark, I pulled the distributor and started spinning it by hand. Doing this I almost gave my Mom a heart attack because my dumb*** only removed the #1 wire and one of the wires I left connected evidently found enough spark to ignite the fuel in one of the cylinders that had its exhaust valve open. It sounded like a 12 gauge going off.
After that happened, I thought it must have spark. I reinstalled the distributor making sure I had the rotor facing the proper direction and tried starting it again. It fired two or three times and then stopped.
I checked all of my grounds, made sure all my wires were plugged in with good connections, tried a spare coil and an old electronic distributor with a different rotor and cap.
I’m suspecting it’s the little blue ignition box but I have an old points style distributor I want to try before I buy anything else.
Is it true that I just run the one wire from the points style distributor to the negative side of the coil? Or am I going to have to rewire the whole ignition system to try it?

Thanks for reading this stupid long thread.
 
Not stupid. First thing I would suspect is the distributor connector---the two pin pickup connector. "Work" it "in and out" a bunch of times to scrub the terminals, and "feel" how tight is it? Those can be troublesome. If you get it running, gently move the wiring to attempt to determine if that is it
 
Unplug the battery wire to the alternator. That wire is connected to all blue wires under the hood including the ballast. You could have a bad alternator and it is shorting the system. You said that is the last thing you installed.
 
Oldmanmopar said:
Unplug the battery wire to the alternator. That wire is connected to all blue wires under the hood including the ballast. You could have a bad alternator and it is shorting the system. You said that is the last thing you installed.
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To be clear he is referring to the light blue field wire, one of two
 
Oldmanmopar said:
Unplug the battery wire to the alternator. That wire is connected to all blue wires under the hood including the ballast. You could have a bad alternator and it is shorting the system. You said that is the last thing you installed.
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Sorry. Should’ve said it’s a one wire internally regulated alternator that goes straight to the starter relay.
 
Shorted distributor . When you were holding it there was no ground to the block. That is why it fired when yo spun it.
 
Only points distributors need a ground to the block.
Electronic distributors work in open air in your hand.
 
TrailBeast said:
Only points distributors need a ground to the block.
Electronic distributors work in open air in your hand.
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But electronics don't work if the distributor is shorted internally unless you are holding it in your hand as I believe he stated he was when he spun it and heard the back fire.
 
Oldmanmopar said:
But electronics don't work if the distributor is shorted internally unless you are holding it in your hand as I believe he stated he was when he spun it and heard the back fire.
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I agree, but that is so rare it would be on the bottom of the diagnosis list in my mind.
Apparently it would be higher up on your list.:D
 
TrailBeast said:
I agree, but that is so rare it would be on the bottom of the diagnosis list in my mind.
Apparently it would be higher up on your list.:D
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F' Y--. Not higher up on my list!! just something that wasn't mentioned that could be over looked from his description of what he did to make it pop. A bad pick-up coil in the distributor shorts to the body. That is what makes them bad. Having spark while holding it but not while bolted in is the sign. It is not rare that a pick-up coil goes bad. But it is a rare way to diagnose it that way. Been there that is why I suggested it. Do you have a problem with me or with everyone. There was no reason to state in a quote."Apparently it would be higher up on your list.:D". You make yourself look like what you are. A trouble making idiot. Troll on. @#$%^&*().. Or find a safe room near you. They have play dough and coloring books.
 
Oldmanmopar said:
Do you have a problem with me or with everyone. There was no reason to state in a quote."Apparently it would be higher up on your list.:D". You make yourself look like what you are. A trouble making idiot. Troll on. @#$%^&*()
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Not at all, and I'm sorry if it came across that way.
I just meant apparently that would occur to you sooner than it would to me is all.
 
After digging through the entire ignition system for a day or so, I’m about 87% sure it’s the ECU that has gone bad again. I can’t wait to get an MSD distributor.
 
I’ve determined it’s either the distributor cap or the rotor (so simple). I’m going to replace them both in the morning.
 
Oldmanmopar said:
But electronics don't work if the distributor is shorted internally unless you are holding it in your hand as I believe he stated he was when he spun it and heard the back fire.
Click to expand...

Trailbeast is a good guy. Your point is excellent and one that I myself might not mention. I often use a spare/ junk dist. for troubleshooting.
 
67Dart273 said:
Trailbeast is a good guy. Your point is excellent and one that I myself might not mention. I often use a spare/ junk dist. for troubleshooting.
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It’s funny because I tried both of my spare distributors. One is a points style and the other is electronic. Neither of them worked so they probably need caps too.
 
Oldmanmopar said:
Shorted distributor . When you were holding it there was no ground to the block. That is why it fired when yo spun it.
Click to expand...
Electronic pickups don't need a ground. Start at the alternator and see what is going on with the charging system first.
 
Oldmanmopar said:
But electronics don't work if the distributor is shorted internally unless you are holding it in your hand as I believe he stated he was when he spun it and heard the back fire.
Click to expand...
Just fired a cylinder full of gass, spinning it will send the spark to all the cylinders but motor rotation is stationary. Scares the hell out of you!:rofl:
 
halifaxhops said:
Electronic pickups don't need a ground. Start at the alternator and see what is going on with the charging system first.
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But if The magnetic pick-up is shorted and it is grounded it will not work at all. That is why I said if he spun it without it being in the block/grounded it fired and backfired. Before you quote me you might want to read and understand what I said .
 
Replaced the cap and rotor. Still not firing up. Pulled the distributor out (with the cap removed this time) and spun the shaft to see if the coil wire would spark against the intake manifold. It sparks great when it spins fast but at low speeds like when the engine is trying to start, it has no spark whatsoever. I guess it’s the distributor pick up?
 
Craig Burriss said:
Replaced the cap and rotor. Still not firing up. Pulled the distributor out (with the cap removed this time) and spun the shaft to see if the coil wire would spark against the intake manifold. It sparks great when it spins fast but at low speeds like when the engine is trying to start, it has no spark whatsoever. I guess it’s the distributor pick up?
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I figured it was the pick-up when you said it fires while the distributor not being bolted in. This is and easy test when diagnosing no spark. Plug another distributor in and spin it. If you get spark your pick-up is usually the problem
 
Oldmanmopar said:
I figured it was the pick-up when you said it fires while the distributor not being bolted in. This is and easy test when diagnosing no spark. Plug another distributor in and spin it. If you get spark your pick-up is usually the problem
Click to expand...
Thank you. Plugged my old dizzy in and got spark while spinning slowly. I’m just going to use this old one because I’m tired of buying new parts.
I’ll report back when I get it changed over.
 
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