Very mysterious electric issue

[NoBudgetGarage]

Hello M body mopar owners
I have the weirdest electric issue, at least to me.
I left my 1980 Dart (yes Dart, Mexican car) without use for a week, today i tried to start it and got no spark.
So i checked the cables from the ballast resistor (4 pin type) (electronic ignition) and i got voltage to the coil. So i assumed the coil was dead so i replaced it and guess what? It indeed fired right up. But since the coil i was using was less than 3 months old i turned the car off and re-connected it and heres the mistery, the car fires right up and ran great all day long.
What could be happening here?

 

[69-]

Epoxy or oil filled coil?

Maybe things got loose inside the coil and and at that particular position you might have had an internal short of the coil?

 

[NoBudgetGarage]

Epoxy or oil filled coil?

Maybe things got loose inside the coil and and at that particular position you might have had an internal short of the coil?

What weirded me out is i didnt move the already installed coild at all, just disconnected the cables, the one i used to start the car was an old one, i just disconnected the cables and the reconnected them back

 

[69-]

That IS strange...

 

[kkritsilas]

Intermittent electrical connection, by the sounds of things. Check the nuts and the screw posts on the coil, and the terminals on wires that went to the coil. Make sure they are all clean and shiny. Just a thought from the problem description. I suppose it could be an intermittent screw post connection inside the coil case as well, but that would require replacement of the coil.

You may want to put dielectric grease on the terminals and posts, depending on how humid Guadalajara is. I remember it getting fairly hot, but don't recall what the humidity was like. The dielectric grease will help keep humidity/moisture away the terminals and screw posts/nuts.