Got a ‘79 f150 with the 400. Replaced the ignition coil a little over a year ago, and now it has gone out again. Still running factory duraspark II setup with (mostly) original wiring, with Taylor wires and motorcraft plugs. Ohmed out the primary and secondary wirings. Primary never settled and was steadily climbing, starting from 9 ohms and higher. Secondary checked out good, measuring at 9.5-10k ohms. Coil was the accel superstock P/N 8145C. Previous one was an MSD coil, don’t remember exactly which one. Can anyone explain why my coil burned up? Or at least help me look on the right places?

EDIT: I’ve bought a Holley Sniper epoxy filled coil and plan on relocating horizontally on intake. I had a 390 in my old 75 supercab and it was mounted this way. Hopefully this will fix my problem. Thank you for all of your tips and tricks. Also, I don’t have the means to put a scope on it, and I’m gonna try to not take it to a shop if at all possible.


FINAL EDIT: After closely inspecting the coil wire, old coil, and distributor cap, I’ve come up with a fairly simple explanation for the cause of my problems. The coil wire never “snapped” into place in the coil. The rubber boot held it in place, but the connector itself was too small to make full contact with the coil side connector. I used a pair of needle nose pliers to slightly widen the wire connector, but one could also use an appropriately sized punch to do the same. Once it snapped into place I knew I had good connection.

 

How is the coil mounted? Vertical or horizontal? It needs to be vertical.

 

it’s mounted mostly vertical. It’s at a slight angle.

Recent pic of engine bay as far as ignition goes.

 

That should be fine.

 

Try one from a dura spark truck from salvage yard, mount it as it was installed on previous truck. Only had one fail in my life that was in 78 on a fairly new truck. Should have plenty of spark.

 

What do the contacts look like under the cap ?

 

Ballast or no ballast? I've used a Accell long ago on a non Ford, it used a ballast, until it died.
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Stock DSII coil on my '77 is mounted horizontal, as it has since 1977 ... over top of the intake in a well fanned air area ...and not down next to a hot cylinder head near an exhaust port. Just having the head, etc close behind it limits air flow over and around it.

 

Personally I would have expected the DS 2 ignition module mounted on the inner fender to have failed first, given your coil choice.
If you want to have a reliable DS2 ignition system it just needs to be stock components.

For example, the accel coil has a .7 ohm primary resistance, compared to a stock coil primary resistance of about 1.1 ohm.
Are you using a ballast resistor?
The more you modified a DS 2 system, the more you reduced its reliability.
Jim

 

Have you bothered to put a scope on it and check the Kv load to the sparks..?

 

Most Ford ignition coils on V8s are mounter horizontally, and 6 cly vertically - its what ever is easier at the factory.
I would suggest buying a Motorcraft ignition coil.