On-Off-On-Off !

[yellow1]

Need some advice here. Last summer my Demon started shutting off while driving normal after about 20 minutes. at the time I was running MSD 6al box with aftermarket distributor, and 40 year old wiring! It would act like the switch was turned off while under power,you know backfiring also. I cranks right back up,then may or may not do it all over again. So this summer I replaced the wiring harness, bumper to bumper with a painless wiring kit, new mallory coil, HEI type ignition, new ignition switch, everything has been replaced. I drove it about 200 miles after all that it started doing it all over again. Not supposed to need a ballast resistor so I do not have one. In my mind I am thinking coil overheating , but it cranks right back up. Has anyone ever seen this before?

 

[RedFish]

I hesitate to suggest something as simple as a bad battery cable. You know what the problem is not. Look at what remains untouched. Good luck

 

[moparlover]

my dart did that once back in the day (backfiring), it was driving me crazy the distributor cap had a crack (hairline could only see it up to the light)
that fixed the problem

the next time it happened i knew exactly what the problem was.

small block dizzys are back by the firewall you have to remove them if you need to even jack the engine 1 inch

if they're cracked you get crossfire - a plug firing when an intake valve is open boom

 

[yellow1]

I did not think of that I will check. Thanks for the Input Redfish !

 

[Bad Sport]

but it cranks right back up.

You say this ^^, does it start back up immediately or do you have to wait a few minutes?

 

[yellow1]

it starts right back up immediatly

 

[yellow1]

It is a 440 not a small block by the way.

 

[67Dart273]

What are you using or a distributor? Wiggle the connector(s) in the ignition. Make absolutely certain the MSD has a good power source. This is three wires, "big black" is ground, "big red" is main power, and "small red" is the switched wire. You can hot wire it to test.

I'd think about running some small wire to first the small red, then the big red, to a monitor lamp / LED so you can see if it's losing power. Check your ignition switch.

Anything else quit BEFORE you touch the switch / starter? Gauges / radio / etc?