Haven't done any work to my '76 other than exterior cleaning. Yesterday car shuts off while driving home from lunch with my wife. Pulled over and verified I had fuel then checked the inline fuse for the MSD box and it looked fine. Pulled the coil wire and turned the engine over found no spark. Get in the car to call Hagerty roadside and noticed the voltage gauge doesn't move, fuel doesn't move but interior lights work, starter turns engine over and the stereo is on.

Replaced the fuse for the MSD box just to say I did and boom fires up. I head home calling Hagerty to cancel the flat bed no sooner do I hang up and it shuts off again. Pull into a Checkers parking lot and try fixing it again since I'm only 2 miles from home but can't get voltage. Flat bed it home and get in the garage and leave it for this morning.

This morning turn the key and voltage gauge works, starts up no problem and ran it for 10 minutes without any problem, everything seems normal. I worked as a mechanic for a few years out of high school and went to the local community college for automotive service technology so I'm not a newbie with cars but have always hated chasing electrical problems. I pulled my multi meter out and verified the fuse I took out for the MSD box was in fact good so that was purely coincidence that it started up. Since I tried another fuse when it shut off the second time and no go that time.

Seems to be vibration or heat related but difficult to diagnose with everything working. In the past ( 3 yrs or longer) I replaced the key switch along with the ignition switch on the column. My gut is telling me the column ignition switch might be acting up.

Any thoughts, suggestions or personal experience is welcomed and appreciated.

Thanks,

Eric

 

First off I'd verify that all grounds are good. Sounds as if the problem could be the MSD box as something internal, solid state, is overheating and then cooling off. Intermittent electrical problems are a bear to find and I've been messing with this stuff since going through electronics school in the Marine Corps in '62. Good luck

 

Figured it out. The wiring harness connector for the ignition switch on the steering column was partially off/unseated. Pressed it back into place and everything is back to normal. Not sure how it happened other than vibration.

 

glad you found it and a big thanks for updating.
too many threads never get a conclusion