I have a 79 F250 4x4 with a 460 Holley 4 bbl. I purchased it recently so I'm not sure what year the 460 is. Casting date on block says D1VE A2B, so a 71? Anyway it has died while going 55mph a couple times. No sputter to sounds, just like someone reached and turned off the key. Once was just a few miles from home (cold engine) another was after a 20 minute trip. I coast to a stop and turn the key and starts right up. The last time this happened was with a engine that had sat for 30 minutes after being driven. I tried to start it and engine fires up while the starter is going (key is turned to start) but dies when key returned to run and starter stops. I pulled coil and resistance is 2 & 9000 so that's ok. I don't have any voltage at the coil unless the starter is cranking, then I have 12v at the coil and good spark. Module bad? Next day I go out there and starts right up and I drive it around neighborhood for 15 minutes and it works fine. Shut it off and starts right back up.

Any ideas?

 

Ignition module?

check connectors and/or try a new one/ backup.

 

X2 on ignition module

 

I was digging through box of stuff previous owner gave me. Behold a ignition module! Yipee. Yeah, didnt fix the problem.
Good news is while sitting dead in the driveway i noticed the cab fan was also quitting. I took the ignition switch apart and sure enough its making bad connections to ign and acc when in on position but not start position. Parts store will have one in the morning!

 

Thanks for letting us know results. All the accessories are powered through the ignition switch so they do take a load. Ford even used to have a replacement pigtail for the switch.

 

It's likely the pick up coil in the distributor.

 

Neither the ignition module or the pickup coil can stop power from getting to the coil. Only the wiring, or the ignition switch itself can do that.
Same for the engine starting to run while the key is in the START position, but turning off once it's back in RUN/ON position.
Both of those symptoms are either the ignition switch, or something wonky with the wiring. No other components (normally) get in the way of power getting to the coil.

I'm sure there are occasional odd exceptions, but those are the usual culprits. Even if the starter relay (which has a connection to the ignition coil in the Brown "I" wire) shorts out internally you would still be able to read voltage at the coil. Same for a failing radio noise suppressor on the positive terminal of the coil. It would stop the engine from running, but you'd still see voltage at the coil wire from the key.

The pickup coil/stator is easy to test though, if there is any doubt DocAdam. Disconnect the distributor plug and measure with your ohm-meter across the Purple and Orange wires. Should read between 400 and 700 ohms. Anything outside of that and you might get it to work intermittently, or it might just decide to go totally dead and leave you stranded.
Well worth checking "while you're at it" in this case.

Paul