I've been tracking down a random stall issue, and I *think* I have narrowed it down to a bad Duraspark module (runs when cold, stalls after warming up, after cool down restarts) but I'm still trying to understand *why* it failed (besides just dropping in a new box).

One thing I was checking is the ignition coil I noticed it was VERY warm, which prompted me to try to check the resistor wire. I am indirectly testing by turning key to "RUN" position, and testing voltage across the "+" terminal on the coil. I'm getting 8.08v when testing from positive coil terminal to ground.

Is that too high of a voltage? I'm not sure how much lower than 12V it should be.

If the resistor wire is going bad, whats the simplest way to repair, given that it appears to at least be partially working. I did go looking for it, but I can't seem to find the actual resistor wire itself (though I understand it's generally behind the dash through the firewall).

Thanks in advance!

 

You're only supposed to see about 8 volts at the coil. That's the way they were designed and, what the resistor wire is there for. Sounds like that part of the ignition system is working like it should. The reason the coil is getting hot when turned to run is the system is sending voltage to the coil with no way to dissipate the heat (by sending a charge to the distributor). The ignition box is another matter, sometimes they fail and need to be replaced. The symptoms you described sound like your box is on it's way out. Do a search on this forum, there is plenty of info about the best boxes to get and what kind (made in China) to avoid.
Mark.

 

Your random stall issue could also be a bad pickup coil in the distributor. You are exhibiting the classic signs of a pickup coil going bad. I'd replace the pickup before the module.

 

 

Easy to check a pickup coil too. At least for the normal failure mode.
Pull the distributor wire connector apart and measure resistance between the Orange and Purple wires. Should fall between 400 and 800 ohms. If it's outside of that range, or frankly even if it's close to either extreme, it's time to replace it.

Have you verified for sure that it's indeed a lack of spark that is causing your stalls? One easy way to tell would be to keep a timing light with you and hook it up the next time it stalls. If you don't see any flashes when cranking the starter, you definitely have a lack-of-spark issue.
If you see flashes at all plug wires though, you will need to widen your search pattern.

Good luck!

Paul

 

Oh, and while that does seem a bit high for an older setup, I've seen readings of between 5v and 9v without any sort of ignition component failure. In all cases the engines continued to run just fine.

Now, on the coil being hot to the touch, personally I've never experienced a coil that was not hot after the engine had been running. No matter what type of ignition, or how may volts were run through it. Always too hot to touch.
I realize that this is not a universal experience though, as I've heard many times people talk about coils that were "warm" or "getting hot" but that could still be handled with bare hands. I've just never seen one myself.

Paul