coils buring up

[killakobra]

My truck has already eaten up 2 coils and is workin on it's 3rd. the truck runs fine with a new one and then it starts to misfire. This keeps going until i have no power left. How many volts should be going to the coil while it's running. i know it jumps 12 to it from the starter solinoid and it drops down after it starts. right now i'm reading 12 volts to the + side. is this a bad resistor wire? Where is it located and how do i change it?

[BobbyFord]

Voltage at the positive coil wire in the "on" position should be between 4.5 and 6.9 volts.

[fordman]

are you still running points or something else. maybe that is eating the coils.

[killakobra]

no, i forgot to mention i'm running Duraspark. i checked the voltage earlier and it was 12. something. not good. After doing a little research i found out that a TFI coil can handle 12. turns out i got one with my parts truck . it's NEVER ran this smooth. i'll keep an eye on the performance and if it starts degrading then i'll have to fix the ballast resistor.

[fordman]

yes the durapsark i think does take a different coil than the points dist.

[killakobra]

i've been using Duraspark coils but they still overheat and fry.

[fordman]

i was looking at the diagram on the site how to hook up duraspark and it showed just a plain 12 volt power supply from the ignition switch only no resistor in the set up anywhere. is that right?

[killakobra]

That's what is frying the coil. it should only be 6 volts

[fordman]

then the diagram on this page needs to be alterered. i also see this diagram has a wire coming and going from the same terminal on the starter relay and it shouldn't. it should come from one and go to the other i think. http://www.fordification.com/forum/view ... =8&t=48178

[70_F100]

then the diagram on this page needs to be alterered. i also see this diagram has a wire coming and going from the same terminal on the starter relay and it shouldn't. it should come from one and go to the other i think. http://www.fordification.com/forum/view ... =8&t=48178

Which wire are you talking about?

[fordman]

it shows two grey wires coming from the s side of the relay . our trucks had one wire to each small terminal. the diagram shows 3. but maybe that is because this is from a mustang site. so maybe those are different.

[70_F100]

I think maybe the legend is confusing. I see that the legend at the top says "gray=existing".

The second wire going to the module is labeled as "white", and, like the other wires going to the module, the wire is colored in the diagram to match the actual wire color.

That's one possible explanation, but I could be wrong.

[fordman]

it was the existing wiring i was talking about. that is why i was thinking it might be a mustang only thing.

[mrtleavitt]

Few years ago I was having coil problems. I burned up a few every couple months. It was mounted horizontally and found out through some research that most coils are oil filled and some types should be mounted vertically. After I changed it to vertical mount I never had the problem again. Just something to think about. I've now bought an epoxy filled coil so I can mount it whichever way I want. It worked for me.

[killakobra]

i had my coil mounted upright but it didn't help. Also, they were burning out in a matter of days, not months. Tfi coils are defiantly the way to go. After i changed mine out the engine ran loads smoother than even a performance CDI coil could manage. here is a picture of one that i used (not my hand). it's mounted to where a fuel pump normally mounts on a 300. The area isn't milled for the pump arm but it still has the holes drilled and tapped.