Quits when it gets hot…

Chopperdriver

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“Brutus”! A ‘70 300 went out for a Memorial Day cruise and he cut off after about 5 miles. Let him cool off and would run about a mile before cutting off again. Thought it was a bad coil, swapped it out but doing the same thing. Temp staying under 190, fuel pressure seems good (electric fuel pump) Hmmmmm… any ideas?

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75LandYacht

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Just my 2 cents, But my 75 NYB did the same thing and it turned out to be the Pickup coil inside the Distib.... OE Chrysler Ignition.
 

CBODY67

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Did it die quickly or only after some spits/sputters/power decrease that indicated something else was going to happen?
 

Big_John

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Since the last owner was also on here, I took a quick look and didn't see where he had any ignition problems like this. It was a Mopar electronic ignition that was added, I did find that. Probably not a bad idea to look over his threads.
challenger

So, with that in mind, I'd be suspicious of the ignition box or the pickup coil being the problem, especially the pickup coil. Since it's intermittent, it's going to be tough to diagnose.
 

Sixpactogo

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The first thing I would do is grab my Ohm meter and test between the neg post of the battery and the case of the ECU. If more than .5 ohms, clean off the paint under the mounting screws. If the case is not properly grounded they get hot and open the coil in the unit. Closes back up when cooled down. It is a common ailment with restored cars because everyone wants nice shinny paint and paint is not a good conductor. Most people don't realize how important grounding is.
 

Chopperdriver

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The first thing I would do is grab my Ohm meter and test between the neg post of the battery and the case of the ECU. If more than .5 ohms, clean off the paint under the mounting screws. If the case is not properly grounded they get hot and open the coil in the unit. Closes back up when cooled down. It is a common ailment with restored cars because everyone wants nice shinny paint and paint is not a good conductor. Most people don't realize how important grounding is.
Great idea! I’ll try that, thanks!
 

Sixpactogo

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It is a place to start and it's a free fix if that is the problem. If not it could also be a weak pick-up coil in the distributor like Big John mentioned.
 

Chopperdriver

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It is a place to start and it's a free fix if that is the problem. If not it could also be a weak pick-up coil in the distributor like Big John mentioned.
I think I’ll replace the whole electronic ignition package to start. Pretty cheap kit and would hopefully eliminate most of the things it could be.
 

CBODY67

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In many respects, "nothing cheap" about the OEM-spec Mopar Perf kit. OEM spec wiring harnesses and such. I've seen lots worse, over the years, than the MP kit. Pretty much plug 'n play, as I recall.

If your little finger hurts, going to chop off your entire arm? FWIW Learn to toubleshoot and diagnose rather than ripping it all out and starting over. In the process of removing things, then putting in something else, you can cause many more issues than suspected, by observation.

Just some observations,
CBODY67
 
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