Burning up coils

[Husker Cuda]

I've burned up 2 coils on my GTX.  The engine starts to miss and a little while longer and it shuts down. I replaced the coil and it fires right back up. The coils are too hot to touch when they die. Any ideas?  440 with MP dist and chrome MP box.
Thanks
Mike

[roadman5312]

points distributor ?   running coil off resistor ?

[Husker Cuda]

No points. I have the chrome MP ECU it has the resistor on the firewall.

[Cudaragtop]

Check the impedance of you ballast resistor.
Depending on the coil you are running you want to have the correct impedance to prevent too high an input voltage to the coil.
Also check voltage regulator and alternator, even with a good ballast you could have too high voltage being passed to the coil.

[FY1Cuda]

Maybe another way of saying it is that if your Coil is always working on the "start" voltage (12v) and not the "run" voltage (8v or something), it's going to burn out.  Could be as simple as the wiring at the ballast resistor.

[Husker Cuda]

Thanks for the info guys. I will check it out when I have time.
Mike

[burdar]

What coils are you using? Some performance coils like the Pertronix Flamethrower, are designed to run on 12 volts. If you installed one of those, you could bypass the ballast all together.

[Bullitt-]

I suppose this applies so I'll throw it out there...researching misfires on my ferd with coilpacks I found it suggested that high resistant plug wires or wide gaped spark plugs can ruin a coil. I would imagine with a distributor a bad cap/rotor could add to this issue.   

[Husker Cuda]

What coils are you using? Some performance coils like the Pertronix Flamethrower, are designed to run on 12 volts. If you installed one of those, you could bypass the ballast all together.

I'm using the P4876732 MP coils so I think I need the resistor. Do you know what resistor I need?  Looks like there are several versions. I'm thinking it should be a P5206436?

I also noticed my ammeter is going almost all the way to the right which could be a bad regulator, correct?

Thanks

[Chryco Psycho]

even a cheap ballast from Napa or similar will help the coil live , you should have 6-8v running at the coil
 it could be a bad regulator or a bad diode in the alt casing the charging problem

[dodj]

I'm using the P4876732 MP coils so I think I need the resistor. Do you know what resistor I need?
Thanks

Does that mean you don't have one now? If not, you definitely need one.
If you do have one on the firewall now,
the factory supplied 'run' ballast resistor was 1.2ohms. If the wiring checks out, Unplug your resistor and see if it is shorted with an ohmeter.

[Husker Cuda]

I have a resistor on it now but not sure if it was the right one for the coil.  I see that the P4876732 blaster MP coils are obsolete now so I will have to find something else.  I will check out my resistor tonight to see what kind of ohms I get.  I will also check my voltage to the coil and see what that is running as well.  How would I know if the alternator has a bad diode?

[Chryco Psycho]

Changing the reg is approx a $15 part so you can try that first or take the alt into a rebuilder & have ti tested

[Husker Cuda]

I pulled the regulator and made sure I had a good ground. Replaced the regulator and checked the resistor. I had right at 1.2 ohms. I checked the voltage at the positive coil and I had around 10.5V with just the key turned to the run position. I fired it up and it was running all the way up to 15.5V at 2,500- 3,000 RPM's.    I checked the alternator Batt terminal and was seeing over 17V. Oh ya I also put a new MSD blaster 2 coil on it.  So can I assume I have alternator problems?  It's a new alternator also as well as a all new M&H wiring harness.

Thanks
Mike

[Chryco Psycho]

looks like a bad alt 14.8 v is approx max you should ever see so at 17 v it is way overcharging , probably killing the coils too