Quits when it gets hot…

[Chopperdriver]

“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?

 

[furious70]

How did it act when you immediately tried to restart?

 

[Chopperdriver]

Fired right back up, maybe a little stumble but never on the starter for more than 10 seconds.

 

[furious70]

I mean did you try before letting it cool down

 

[57fury440]

Is it electronic ignition? If so, it could be the box.

 

[Knebel]

Faulty Condenser if points!

 

[75LandYacht]

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.

 

[Chopperdriver]

I mean did you try before letting it cool down

Yes, that was the immediate restart, after it cooled down for a few minutes it would fire right back up.

I mean did you try before letting it cool down

 

[Chopperdriver]

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.

Previous owner put electronic ignition on it.

 

[CBODY67]

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

 

[Chopperdriver]

Is it electronic ignition? If so, it could be the box.

Yes, EI, probably less than 1,000 miles on it, previous owner never drove it much.

 

[Chopperdriver]

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.

Previous owner put electric ignition on it.

 

[Chopperdriver]

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

Cut off just like you turned it off with the key, no warning at all.

 

[Big_John]

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]

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]

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]

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]

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.

 

[Sixpactogo]

It sounds like it was a recent install. It may be a waste of money if it was only the grounding problem.

 

[CBODY67]

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