What is my ignition problem?

[PurpleBeeper]

70 Road Runner, 440, Mopar electronic distributor, MSD-6AL, MSD Blaster coil, no ballast resistor.
Last weekend I had a cough out of the carburetor. Today I had the engine cut out 3 times for about 1-second going down the highway with one backfire out the tailpipe. Fuel pressure was good & tachometer dropped to “0” for 1-second each time it cut out. So, I’m thinking ignition. Ideas? My “guess” is since it was after the engine was fully warmed up, maybe the coil or ignition box is going bad?????

 

[Belvedere408]

From my experience when my coil went bad my car would just shut off. I'd have to let it sit for a half hour or longer then be fine. It ended up being my bulk head harness burning coils.

 

[PurpleBeeper]

From my experience when my coil went bad my car would just shut off. I'd have to let it sit for a half hour or longer then be fine. It ended up being my bulk head harness burning coils.

What exactly about the bulkhead disconnect? I did put an Autozone coil in there today. The MSD Blaster was really hot when I took it out (1/2 hour after car turned off)

 

[Sixpactogo]

I am betting on the bulkhead connections going thru the firewall giving you some intermittent loss of continuity. Usually when a coil or the CPU fails it shuts down immediately.

 

[Belvedere408]

What exactly about the bulkhead disconnect? I did put an Autozone coil in there today. The MSD Blaster was really hot when I took it out (1/2 hour after car turned

My bulkhead connections had been cut into and spliced numerous times over the years. Car started killing distributors and coils. The distributor would break up at above 2500 RPM and the coil would just shut the engine off. I was stubborn at first since I had just paid 10k for the car 18 years ago, didn't wanna replace the entire wiring harness. But eventually did replace harness last year.

 

[pnora]

with the tach dropping out its either a loss of feed to the system or the distributor pickup possibly going open and causing the ignition to momentarily shut off. I would check the reluctor and the gap in multiple places.

 

[Bird 426]

I've had 2 coil failures. They acted differently both times.

 

[Geoff 2]

This could be many things. If vac adv is being used & has done a lot of miles, the p/up wire could be broken. Every time the VA actuates, it flexes the p/up wires.

 

[HALIFAXHOPS]

As per coils going bad 90% of the time they are not the right ohm rating for the system. The new MSD 6AL have a ton of issues also. Pickups do crap out hot and cold so do the ECU's run from the parts store stuff fine the right older stuff. It is still around.

 

[PurpleBeeper]

with the tach dropping out its either a loss of feed to the system or the distributor pickup possibly going open and causing the ignition to momentarily shut off. I would check the reluctor and the gap in multiple places.

So, you don’t think it’s possible it’s the coil based on my description?
1. It’s an old MSD 6AL (at least 10 yrs)
2. Vacuum advance not used

Does anyone know the correct coil ohm rating of the top of your head?
Also, any idea what my relictor gap should be?
Thanks everyone! I’m trying to drive to work in it this morning (only car available)

 

[HALIFAXHOPS]

Gap .008-010 on a oem mopar. Check it all around to make sure the shaft is not bent also. Coil has to match the ecu you have MSD should have it listed.

 

[PurpleBeeper]

Gap .008-010 on an oem mopar. Coil has to match the ecu you have MSD should have it listed.

Thanks. Please explain “match the ECU”? I just put an Autozone coil on there last night (all that was available) and stuck my MSD Blaster coil in the trunk)

 

[HALIFAXHOPS]

Look and see what coil recommends for that 6al

 

[PurpleBeeper]

It’s not the coil. Car drove fine for 30-40 minutes, then really started cutting out bad with backfiring.
Engine & dash wiring were replaced 5 yrs ago
Heads were recently off
I checked the bulkhead blue wire from the engine side & it seems tight. It’s sealed in that wire only, so I can’t push the connector in with a small screwdriver (engine side)

 

[PurpleBeeper]

“Might” be the blue ignition wire (?). The spade connector was only 1/2 way in….so “maybe”
Update - that wasn’t it. Engine still cuts out