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So I'm changing out to the PinzSSI. Ordered all the items from Rick, received, and all laid out in the garage.
That said, today I'm working in the front of the Pinz, cleaning out the air duct. SSI install is about item 50 on the "To Do" list.
I hear this loud bang, smoke start in the front.
The coil literally exploded, with the end piece popping off - wires everywhere.
Any ideas what could have caused it?
Short in the wiring?

Not a big deal with the SSI changeover just moving to No 1, but it would be good to know.

Coenraad

Was it the original coil or a Pertronix that exploded?
There was an issue with some Pertronix coils a few years back but I don't recall that they exploded.

Pinz SSI is an excellent setup BTW.

Judging by the condition, its a Bosch, but not the original mil version. Distributor is the civvy conversion, without Pertronix.

Literally melted the stuff inside and blew it all over the insides. Luckily I had the cover and seat out, and could get it out with thick leather gloves before anything else ignited.

SSI aside, I'll keep a spare traditional set - just in case.

Never a dull moment with this reno!

Coenraad

Make sure you're not getting too much voltage to the coil.

I'll double check today before I install a replacement.
What is too much? With both batteries independently charged I get about 27V for a short period.

Coenraad

Paul

Took everything out - it was indeed the pertonix system. Everything smoked - coil, and pertronix module in distributor. Just melted plastic. Looks like a massive short - it melted the wiring clean off the pertronix module.
Installed the replacement set - and had to fiddle a bit with the distance in the distr. The supplied half-moon did not allow positioning close enough for pickup.
Everything good now, until the PinzSSI is installed in a week or two.

Sometimes the stuff you buy as "extra" comes in mighty handy!

Coenraad

What [coil voltage] is too much?

I typically see 16-17V at the coil positive terminal when the engine is running. The ballast resistor is what causes the voltage to drop from 27V down to about 17V at the coil.

many years ago my coil puked out, what looked like white ceramic ooze. the petronix igniter was melted as well. some of the wiring in the pinz harness was hot as well. Never did find the problem. I reinstalled points and original ignition system back in until I was sure there was no further issues. When the new petronix arrived I installed it without issue and drove the truck that way for many years. Now of course it is running the SSI system and still no more signs of any ignition related issues.

Jim

I'll measure today with the temporary replacements. If the resistor is fried, it should not be running (and it is) - unless there is a parallel circuit somewhere. I could not find anything on the wiring diagram.

4x4Pinz - You describe what I experienced exactly... The explosion was violent enough that I'm still cleaning the white stuff from the rear firewall.

I spoke with a friend who specialises in vehicle restoration/hot rods, that kind of thing. He mentioned that he's seen it before as well. They started installing an extra resistor to reduce the voltage further. He was impressed by the PinzSSI though, and said that "that's the way to go".

Coenraad

If the resistor is fried, it should not be running (and it is) - unless there is a parallel circuit somewhere. I could not find anything on the wiring diagram.

There is a parallel circuit - the starter switch itself. The reason for the ballast resistor is that when the engine is cranking, the battery voltage is lower (and may be very low) so the ignition circuit is designed for that lower voltage. Once the engine has started, the voltage goes much higher so the ballast resistor is used to reduce the ignition voltage back to a lower value as to not overstress the system. The ballast resistor also helps to limit the energy that the coil could ever get, but obviously not limited enough to prevent the coil from disintegrating! There is an additional contact on the starter push button that supplies direct battery connection to the coil, bypassing the ballast resistor. Releasing the starter button should break this connection and now power must flow through the ballast resistor to power the coil. So you should see 'full' battery voltage at the coil positive terminal (+) during cranking (maybe 20-22V) and roughly 16-17V (not a terribly critical voltage) once the truck is idling. You can check both to ensure that they are working correctly as well as that the wiring has not been messed with, or damaged during the meltdown.

Thanks Jim

I'll check values tomorrow evening.

Coenraad