Very hot coil - no spark

[Poke]

my 302 died suddenly last weekend. The coil was hot, very hot. So I put a new coil on it. Now when I try to start it, it wont run, AND the coil gets hot again. The coil gets too hot to touch just by starting it.

We had power out of both sides of the resistor when we checked with a test light. Could the resistor have gone bad and allowing too much voltage through?


It has an Atomic EFI system but I need to make sure it is not that. It does not control timing.

 

[SeanT4x4]

Went through something like this just recently. The first things I would look at is the wire from the coil to the dizzy, and in the dizzy cap. If there is no place for the voltage to go the coil will get very got, and burn out. Same goes for if its having to jump a huge gap in the cap.

 

[Steve83]

All the heat comes from the PRIMARY winding - the 12V side. A fault (including too much gap) on the 2ndry side (high voltage) may burn through the insulation in the coil, but it won't directly cause heat.

 

[MarsChariot]

Sounds like a classic case of 12 volts being applied continuously to the coil instead of the specified 6-8. That will burn them up every time. Measure the voltage on the positive terminal of the coil. 12 volts is too much and you are somehow bypassing the resistance wiring in the ignition circuit. It the circuit is non-OEM, you will need a ballast resister to drop the voltage to 6-8.

 

[DirtDonk]

If you're not familiar with just how hot they normally get, it could feel like it's getting too hot as well. They do get VERY hot (too hot to touch) just from normal running.

How is the rest of your electrical system? Any EFI setup, whether stock Ford from the junkyard or a brand new TBI setup like you have, will always appreciate the newest and cleanest of connections everywhere. Not just for it's own use, but so the rest of the system is smooth and quiet too.

And did you verify that there is no spark at a plug? You can do this easily by connecting an inductive timing light to any wire (all of them is helpful too, just in case) to see if you get a flash when cranking. A flash means you have spark. No flash and you know you're on the right track.
Just wondering about that, since with an EFI setup you now have plenty more possible trouble ares to deal with.

Good luck.

Paul

 

[broncnaz]

Usually its the other way around when a resistor fails in that no power comes thru. Coils do get hot and without the engine running it will get hotter than normal. Thats why theres a acc. position on your igntion switch so you dont fry the coil when you want to listen to the stereo with the engine off.
What ignition system are your running?