Duraspark system is killing coils

[JonH74538]

Good afternoon everyone,

I have recently installed a duraspark system in my 72 f2500. I used a new NAPA distributor and an ignition module with the blue strain relief. My first coil was an accel superstock coil. I ran a full 12volts to the coil. The truck ran fine for about thirty miles until the coil died. I replaced it with a duralast unit from my local AZ. The coil is for a 1978 ford truck and says 12v coil on the canister. This coil lasted about fifteen minutes. I traded it under warranty and added a ballast resistor and closed the plug gap to .040. This time it lasted about ten minutes as well. each time the coil goes out, it is after I really lean on the accelerator or down shift to pass someone. I am lost. I am beginning to think that my voltage regulator may be going bad and burning up my coils. Do you guys have any ideas what may be killing the coils?
-Jon

[basketcase0302]

"JonH74538"Good afternoon everyone,

I have recently installed a duraspark system in my 72 f2500. I used a new NAPA distributor and an ignition module with the blue strain relief. My first coil was an accel superstock coil. I ran a full 12volts to the coil. The truck ran fine for about thirty miles until the coil died. I replaced it with a duralast unit from my local AZ. The coil is for a 1978 ford truck and says 12v coil on the canister. This coil lasted about fifteen minutes. I traded it under warranty and added a ballast resistor and closed the plug gap to .040. This time it lasted about ten minutes as well. each time the coil goes out, it is after I really lean on the accelerator or down shift to pass someone. I am lost. I am beginning to think that my voltage regulator may be going bad and burning up my coils. Do you guys have any ideas what may be killing the coils?
-Jon

Jon,
Two things to look at, (and hopefull;y some other guys can chime in here as well).
I'd look real hard at your grounds, (in particular the intake to cowl/cab ground strap most guys trucks have had "butchered"/removed).
Agree you might be onto something on the voltage regulator, (they're cheap enough to throw a new one in to make sure, (rather than be stuck on the side of the road).
Loved my "Durapuke" (what chebby guys call our duraspark LOL) ignition and is how I got my username! My 76' Early Bronco had it and the PO gave up on it as it was frying the boxes everyu thime it hit a bump! I had to unravel the entire wiring harness to find where he had pierced the harness so when the Bronco hit just the right bump in the road it would fry the box! The rest is history as I kept that running gear on the road over 20 years and never rreplaced another box on it!
Duraspark tried and true!

[1972hiboy]

Have you had a multimeter on the + side of the coil while its running to see what reading your getting? If a voltage regulator is stuck you would see 15+ volts, that could kill a coil. If the alternator lost its ground that would spike voltage up too and kill a coil. Butt like Jeff said comb over grounds but I would be curious to see what the multimeter is saying while its running.....

[JonH74538]

I checked the voltage regulator. It charges the battery to 14.53 volts at around 3200rpm. I am going to clean up all of the grounds tomorrow. I did double check that the ground from the cowl to the intake was intact. Is there a certain way that this coil needs to be mounted? It is currently mounted vertically on the side of the ac compressor.

[basketcase0302]

"JonH74538"I checked the voltage regulator. It charges the battery to 14.53 volts at around 3200rpm. I am going to clean up all of the grounds tomorrow. I did double check that the ground from the cowl to the intake was intact. Is there a certain way that this coil needs to be mounted? It is currently mounted vertically on the side of the ac compressor.

14.53 sounds good but after running for awhile it should be dropping back to around 12 volts, (once the battery has reached it's full charge usually within 15 minutes if there's no load on the battery).
I'd "remotely mounted" coils even on the inner fender before with no issues, (as long as it is properly grounded).
Here's the 358 mile 1970 Ford Explorer's factory coil location, (I always had an issues with mounting my coils to the intake or front of the engine where the heat is known to shorten the life of them).

Edit: Keep in mind mouinted on the AC bracket your now relying on that having paint free/rust free grounding to the engine block as well.

[JonH74538]

Today, I cleaned all of the grounds. I replaced the ground from the intake to the firewall. I also remounted the ignition coil in the factory location and checked the voltage at the coil while running. It is getting 10.5Vdc at idle and 12.5 Vdc at 3000rpm. Does that sound correct?

[basketcase0302]

="JonH74538"Today, I cleaned all of the grounds. I replaced the ground from the intake to the firewall. I also remounted the ignition coil in the factory location and checked the voltage at the coil while running. It is getting 10.5Vdc at idle and 12.5 Vdc at 3000rpm. Does that sound correct?

Wouild like a second opinion here but pretty sure the coil needs a full 12 volts to run the Duraspark ignition , (I don't have a Duraspark vehicle here or would verify this).
Our trucks come with a resistance wiring feed wire from the ignition switch to the coil to purposely drop the voltage as to not "fry" points with constant 12 volts.

I'm pretty sure you'll need to run a new feed from inside the cab, (back of the ignition switch) out to the coil to make sure it's getting a full 12 volts and making sure it is a coil rated for the electronic ignition's full 12 volts.

Hoping someone else chimes in here to confirm please...

[JonH74538]

I had a full 12 volts going to the coil but added the ballast resistor when the third coil failed. I returned the coil that I bought at AZ for a refund after the second one failed. I ordered a standard motor products fd476t coil. It says 12volts electronic ignition on the side of the coil. I will take the truck out tomorrow to see if it is fixed. I bought an extra coil. It was ten bucks on Amazon, way cheaper than a tow bill.

[JonH74538]

I believe that the poor ground was causing the issue. I drove it for half an hour with the ballast resistor installed without an issue. I have since removed the ballast resistor and I am running a full 12vdc to the coil without any issues. Thanks again for everyone's help!

[basketcase0302]

Agreed on the spare coil being cheaper than a tow bill, (you shoulda seen all the spare parts I used to carry when I owned my airboat and last bump LOL! That old saying about "everything but the [censored] sink...