Ignition Coil Overheating

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traffical

traffical

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I have a 1966 Barracuda that I have restored. I have an electronic ignition module and distributor. I had the electronic ignition before and had 100,000 miles without a problem. My problem is that the ignition coil overheats and the engine stalls out after about 15 minutes. I am at my wits end as I have gone through the wiring several times at that seems OK. I have replaced the plus, plug wires, rotor cap and rotor, ballast restore, ignition module and coil. Still have the problem. I checked the timing and that is OK. I checked for excessive voltage and the alternator is putting out 13.18 volts at 1000 RPM which seems OK. Still the problem persists.

I am running out of options or places to look. Anybody have some ideas of where to look next?
 
Are you running a ballast resistor? You should not have battery voltage at the coil in run mode.
 
Yup, ballast? And......coils can be "partially bad." Measure coil voltage "running."
 
I do have a ballast resistor. I have also changed the resistor. When I changed the ballast resistor I checked it and have a reading of 1.0 ohms. I have also measured the voltage on the + side of the coil with the engine running. I have a reading of 7.38 volts on the positive side.
 
Horizontally mounted to the intake manifold behind and to the right of the carburetor
 
It's a stretch, but make sure the two posts are located in a downward position so both fields are bathed in oil.

Did you replace the coil? If not it's quite possible it's bad.
 
Thanks for all the help. I can't tell you how much I appreciate talking to someone about this as I have been pulling my hair out. To answer your question, the terminals on the coil are horizontally. That is to say that they are both on the same level and level with the high voltage output terminal.
 
.............It does sound like the coil is bad, but r u sure its not the pick up coil in the distributor overheating? I've had that happen a few times......kim.........
 
10 to 1 on distributor pick up vs coil. IM not saying it cant be coil but pickup goes bad times per coil.
 
Thanks, I had not thought about that. I will look for a replacement and give that a try. Might be next week before I have it in hand and can give it a test and get back to you. Really do appreciate the help.
 
Mind if I just watch this one? I'm pretty curious about this....:happy1:
 
The 7.98 volts coil + running is a pretty good value. The 1 ohm ballast resistor when cold is a good value; make sure this was measured with the wires removed from one lead on the ballast. Run the car for 5 minutes, shut it down, quickly pull the wires off of one end of the ballast resistor, and very quickly measure the ballast resistance. It should be around 2 to 3 ohms hot after idling for a few minutes.

Measure the coil resistance cold; should be around 1.5 ohms.

Are you running an orange or silver ignition box?

Does the intake manifold have the exhaust manifold heat passage? If so, if the coil is mounted near the center of the intake on either side, then it can pick up heat from that passage.
 
We MAY be on the entirely incorrect track here.

Have you checked for spark when it quits?

COULD also be ECU or pickup, as someone mentioned

As much as I hate "throwing parts" this can be difficult to diagnose
 
Ignition coil failures are rare but they can happen. Can coils have a slug with two windings made with enamel coated copper wire. A turn to turn short is a disaster, significantly loading the coil resulting, in a weak spark. The short may be intermittent, related to internal expansion and degraded insulation. Checking coil resistance is not helpful, because one shorted turn out of 100+ is in the mud.

As Del suggests testing can be difficult. It involves testing hot, looking with scope, or inductance measuring equipment. With a spark tester it may be necessary to close the gap to see a faint orange spark.
 
traffical said:
I have a 1966 Barracuda that I have restored. I have an electronic ignition module and distributor. I had the electronic ignition before and had 100,000 miles without a problem. My problem is that the ignition coil overheats and the engine stalls out after about 15 minutes. I am at my wits end as I have gone through the wiring several times at that seems OK. I have replaced the plus, plug wires, rotor cap and rotor, ballast restore, ignition module and coil. Still have the problem. I checked the timing and that is OK. I checked for excessive voltage and the alternator is putting out 13.18 volts at 1000 RPM which seems OK. Still the problem persists.

I am running out of options or places to look. Anybody have some ideas of where to look next?
Click to expand...

It looks like the only part that has not been changed is the mag pick-up!
So, just to be sure; Have you have proved the no-spark symptom, by removing the coil center tower wire and performing a spark-test? I didnt see you post that result in any of your posts.
 
There are some new suggestions which I appreciate. There were several questions that I can answer. First I measured the resistance of the ballast resistor warm but not hot. Second I have checked and there is gas but no/weak spark after the engine quits. Things have to cool down before I can start it up again and when cool it fires quickly and is ready for the races. My problem is that I have to get to the races within 10-15 minutes.
 
Gang:

Well I am not sure but I think my problem is now solved. I'm not sure but I do think it was the Mag-Pick-Up. Thanks for all the great suggestions
 
Bad Sport said:
It's a stretch, but make sure the two posts are located in a downward position so both fields are bathed in oil.

Did you replace the coil? If not it's quite possible it's bad.
Click to expand...

If I may,the coil location,is it that important that the org coil be mounted on its side.Mine is straight up mounted on the firewall,just figured that on the intake it would get to hot.:???: I have no problems as yet but we are going on a trip next week short drive 80 miles non stop.What you think.
 
I have another question. I dropped in a new Billet distributor and the wire connection was different than what I have. The distributor instructions identifies the leads to the ECU as Positive and Negative which is fine. My problem is there connection to the ECU. I looked at several wiring diagrams which show the leads from the distributor to the ECU but none late whether Pin 4 on the ECU is Positive or Negative.

Does any one out there know whether Pin 4 on the ECU is positive or negative?
 
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