Coil eruption!
 

I started my 39 PU today and decided to let it idle for a while. After about fifteen minutes it stopped running. When I approached it I found the coil was spewing black tar out where there is a gasket around the top. I removed the old coil and put on another coil I had. The truck started up and ran fine with the newly installed coil.
Any ideas about what could have caused coil to fail or just a common occurrence?
Thanks

Ps
Motor is a 44-48 flathead with coil mounted at front left of block.

Re: Coil eruption!
 

What voltage? Type of coil?

Re: Coil eruption!
 

Sorry, it is a six volt and is the round type that mounts to top left on the intake manifold. It has the two connectors on top and large wire on bottom.

Re: Coil eruption!
 

Just an old coil. I've seen this happen on other types of older coils too. Both 6 & 12 volt
Hopefully you have tyhe correct resistor installed

Re: Coil eruption!
 

And the resistor was connected?

Re: Coil eruption!
 

More info. The only wiring is: Bottom of coil wire to "crab" and one wire from top of coil to distributor and other wire from top of coil to battery negative post. The new wiring harness is not hooked up at all. This setup allows me to start and run engine without worrying about the wiring.
Thanks

Re: Coil eruption!
 

I guess doing it the way you are you don't have to worry about the ignition
resistor either.:eek:

Bob

Re: Coil eruption!
 

If it was just hotwired to the battery you most likely overheated the coil. Was it hot? If that is the case the same thing will occur with the new one. But, it really depends on what the resistance of the coil is. What is the coil resistance? Where are you getting them?

Re: Coil eruption!
 

The first coil was just an old one I bgt. To have an extra. The second is the one that was on the truck - I just received it back from Skip Haney - where he rebuilt it. The coil that went bad did get hot and melted the inside of the coil and spewed out hot tar substance.

Re: Coil eruption!
 

Did Skip say anything about it needing a resistor or not? You really need to know the resistance of the coil. I would suggest you not run the engine or put power to the coil until you know what you have. If you wanted to check something and just run it for a minute or two that would be ok, but not longer. Do you know how to check the resistance of the coil? or did Skip provided anything saying what it was? What was the purpose for running the engine for 15 minutes the first time?

Re: Coil eruption!
 

I will go thru Skip's papers and find out.
Thanks for your patience.
Randy

Re: Coil eruption!
 

The info. just said that he uses "standard Ford resistor made to run on 6 volts". I will now just put the new wiring harness on and not use the short cut anymore. Thanks for your help once again.
Randy

Re: Coil eruption!
 

Like I said, it is ok for short periods of time, but not more than that. You (as you now see) will overheat the coil. Need any help with the harness install just let me know.

Re: Coil eruption!
 

With the information that you have already provided on the wiring, I feel good about it. I certainly will let you know if I run into another "volcano".
PS, I remember when I removed the intake manifold a couple of months ago, there was some black very hard substance on top of the motor block between the manifold and the head - behind the coil. At the time I had no idea what it was or had been. Now I know that it was the hardened "goop" that came out of a previous coil and was just like todays. In a morbid sort of way, today was amusing. The black liquid spewing out of the back of the coil at the top and going all over my clean motor and polished alum. intake manifold. I survived and the flathead sounds wonderful. Love at first sound.

Re: Coil eruption!
 

Hopefully you weren't letting a new engine idle!

Re: Coil eruption!
 

The paperwork that I have on the engine shows that it last ran in 2002. That is why I am so pleased that it runs and sounds so good.
Randy

Re: Coil eruption!
 

Don't run Skips coil without a resistor or you will melt that one. I'm
surprised it had a melt down running. Are you sure it didn't stall?
I have seen a bunch of melted stock coils and a few Skip rebuild
that were sent back but all were do to the ignition switch being left
on. If the points happened to be open it won't hurt the coil but if
they are closed the coil windings are dead shorted to ground and
heat up like the heating element in a toaster. Are you sure you had
a 6 volt battery and was there a battery charger running? G.M.

Re: Coil eruption!
 

G.M. I started the truck and thought I would let it run a little (it has been 14# years since it has run) as I was right there piddling around. In just a few minutes the engine stopped running and when I walked over to the truck, there was black gunky tar like substance spewing out of the top back of the coil. I jerked the wire off the coil (the one to the battery) and then I removed the coil and started cleaning up the mess.
The battery is a six volt and the coil was one I had bgt. to use as a backup. After I bgt. it I became aware of Skip and sent him the coil that came on the truck when I bgt. it. In the meantime I decided to hot wire the truck and I then used the backup coil to start the truck and it is the backup coil that did the eruption. I now have Skip's rebuilt coil on the truck but I have decided to not start the truck by hotwire anymore. I am now in the process of installing a new wiring harness. It is a learning process and I am really enjoying learning.
Thanks
Randy

Re: Coil eruption!
 

I am thinking your coil had the beginnings of shorted internal turns in the primary and/or the secondary windings. As your engine started and was let run, that short became worse until the coil totally failed. The internal heat caused by the shorting will cause the tar looking compound to melt and flow out of the case/housing. I have some early helmet distributors that have their aluminum housings covered with that mess.
I have also seen another type of catastrophic coil failure where the battery kill switch was in the open/off position and the owner wanted to see if he could drift start his car with the ignition switch on, the transmission in gear, and then let out the clutch when the car got rolling fast enough. The car did start without the battery in the circuit and the generator produced a higher than normal voltage and way too much current flow through the circuit because the normal internal battery resistance was no longer in the charging circuit. Things started burning and the internals of the coil got so hot that the top dome shaped part of the coil housing completely burned away. Never saw a coil that was so burned up before seeing that one, in my entire life!!

Re: Coil eruption!
 

If you want to run it just put the resistor in the hot wire. I still think
it shut off and you didn't realize it for 3 to 5 minutes. It doubt
it would just shut off, it would start running funny when the coil got
hot before it shut off and if the points were closed when it stopped
the coil was already heated up would melt. It takes 10 to 15 minutes
to get a cold coil hot on the test machine before it just starts to melt.
Even a slight melt down don't usually hurt the coil, infact the original
tar melting a little dries it a little and seals it better. A lot of times
the battery runs low on voltage before the coil gets bad. The worst
melt downs are with a battery charger on. G.M.