Ignition coil heat up

[Pedromtt]

I have a 1979 Fiat Spider with electronic ignition, it drives good for about 10 miles then shuts down, cause the ignition coil stops working; it heat up. The car starts after two hours. I have replaced the coil and ignition module but the problem persist. What can cause a new coil to heat up and cool after two hours? Pedromtt

[divace73]

As a guess, it may be your spark plugs, are they the resistive type specfifed for the car?? or your swiching module under the coil, was it the original magnetti marelli coil?

[vandor]

Pretty much the only other thing that is left that helps produce a spark is the pickup coil in the distributor. Check the 2 wires in the distributor for cracked insulation. I have not heard of these things going intermittent, but that does not mean it can't happen...
I assume when this happens you have checked for 12 volts at the coil.

[So Cal Mark]

I've seen several pick up coils fail intermittenly. Coils are filled with oil to cool them, they get very hot

[Pedromtt]

Thank you guys,
I have replaced plugs, plug wires, ignition module (under the coil) and ignition coil, I will replace the ignition pick up at the distributer. I did a light bulb test last time it happened on the + and - sides of the ignition coil and the bulb was bright on both side. I am under the impression that the negative side should have less voltage therefore a dim light. The - is powered by the ignition pick up at the distributor. Is possible that the ignition pick up gets hot and short outs, which causes continued 12 volt current to the negative side of the coil and that causes the ignition coil to heat up. I will replace the ignition pick up at the distributor and report what happens, in the next few days.

[majicwrench]

You're not quite correct.
The pickup powers nothing. It send a signal to the module.The B+ comes into coil at( +), and exits at (-), then is grounded thru module. then, when the time is right, the ign module gets a signal from pickup and opens the circuit, which produces spark at coil.
So, if you have B+ at (+) that is good. If you have B+ at (-) all that means is that the module is not grounding the coil at that moment. Need to crank engine, (-) at coil should alternate tween B+ and ground.
IF you crank motor and (-) stays at B+, for some reason module is not grounding coil. Could be module, pickup, wiring or dist not spinning to name a few.
Keith

[vandor]

>I am under the impression that the negative side should have less voltage therefore a dim light

It's usually only a little less voltage, not enough difference to notice on a lightbulb.