Well its been over a year since my 76' FE ran correctly, which gave me a chance to rebuild the C6 last year, but she wouldn't run right when warmed up, acted like a ignition or gas delivery problem, stuttering and backfiring, but at idle was perfectly fine. So i got fairly defeated and it went on the back burner while I tried to troubleshoot it on the weekends while other projects took priority, like my sons Tacoma engine swap (dont ask).... Well ive been cleaning up my shop and building motivation to pull the ol'e truck back in, then seen a facebook post by a fella who just replaced all his ignition parts and now his truck would start, run act weird then die, not my exact symptoms but the conversation resulted in discussing the resistor he installed with his new coil and several folks pointed out that he does not need an additional resistor because the duraspark module already has a resistor build in it and this causes a lack of correct voltage to the coil and thus a lack of correct voltage to the distributor.... Well then the light bulb went off .... I being the super-smart man i am, added a resistor to my coil setup in the summer of 2019 cuz well it was in the box when i got the new coil and according to the instructions, it needed to be there, and at idle it showed the correct voltage and Ohm. So yesterday i bypassed the resistor, started the truck and went for a spin......ZERO PROBLEMS ! Truck ran like a swiss watch ! (minus some leaks and brake issues im still dealing with)...... I was in disbelieve and still am, waiting for the other shoe to drop....

im sure there was some other way for me to test this and find the problem sooner, but here I am now...... my real question is why did this not really affect the truck at idle but only when it was driving ? Can this really be the fix ? The wire below was coming from the resistor to my coil and it was the culprit the whole damn time ! So needless to say im like a kid whos dirt bike just got fixed, got my list of repairs and fixes to make before shes totally road worthy, but hot damn im excited again.... Oh and by the way my C6 rebuild ran great, shifted firm, no issues, and that was an accomplishment for me.

 

Not sure what resistor you're talking about, do you mean the one on the coil for the radio or one you added.

The durashart does use a resistor wire to the coil , it's not in the ECM. but if you used that in conjunction with a resistor coil I can see how it would cause problems.

Ford never intended the coil to have the full 12v, but I'm sure it would run fine on it until it doesn't .

 

"my real question is why did this not really affect the truck at idle but only when it was driving ? Can this really be the fix ?"

Air and vaporized gasoline both act as insulators, so as compression increases and more gasoline is added to the combustion chamber more voltage is required to produce a spark. At least that's the idea behind higher voltage ignition coils and plugs in forced induction vehicles.
So at off idle you'd have more gasoline in the combustion chamber. Possibly just enough to not get a good spark.

Just a guess.

 

When I first bought my Dent and didn't know much of anything about them the PO had told me he rebuilt the entire ignition system. Fast forward about 3 months and I had an small engine fire while sitting in traffic. The plastics on the distributor and ignition coil had caught fire. Luckily I was coming back from a kayak trip and had a soaked shirt I could smother the fire with before it could get out of hand. After a tow home and a little investigating I found that the resistor wire had been removed completely and the ignition system was running on 12v at the time of the fire.

So you're right it will run fine, till it doesn't.

 

It feels good to fix a longstanding problem, and the more mysterious the problem, the better it feels to fix it.

 

Congratulations! Feels great!
The instructions probably said something along the lines of "needs the resistor if one is not present already" but you won't find one like you had in your kit, because Ford did not, or at least rarely used an external ballast resistor. Always a length of resistor wire between the ignition switch and the firewall. So yes, your coil was getting insufficient voltage.

As mentioned, the module itself does not usually have a resistor inline. However there were some years (don't know what color the modules were) that did have a resistor in at least one of it's power sources. However most, including the blue grommet module you might have(?) did not use one.

Not sure what the wire was for. Where did it go to and from exactly? And did you make it when you installed the parts?

Paul

 

It was just the wire coming from the resistor to the coil, a symbol of my frustration, may tape it to the beer fridge for good measure...

 

My question was to get more detail. As in, what side of the resistor did it come from, and which side of the coil did it go to? Assuming the positive side of the coil, but what side of the resistor?
And presumably it was not the only wire from the resistor? You should still have power to your coil's positive side with the key on. Which of course you do, or it would not run. But curious what wire is still there now.

Thanks

Paul