Several years ago, I converted the inline 6 in the 66 to a duraspark II ignition. It has started very reliably with the electronic ignition conversion for years but has had a couple no start issues in the past couple weeks. Both have been when it has been north of 90 degrees out and both times after sitting for at least a day. It will start normally, but immediately dies. Sometimes I can hold the accelerator down and it will struggle but stay running but as soon as you let off the gas and it drops back to idle it dies. After doing this a couple times it would not stay running even with the gas pedal mashed down. while trying to get it started, I can smell fuel and removing the fuel line allows lots of fuel flow so I believe its getting fuel. I also went through the carb a few months ago and rebuilt it. Perhaps it has a clogged jet or something but unlikely as the fuel filter was replaced along with plugs, wires, cap and rotor at the time of the carb rebuild. All of this has me wondering if the Duraspark module is bad or heat sensitive. I'm tempted to go buy a new one but I hate buying parts and crossing my fingers. The most recent no start was yesterday afternoon in the heat parked in the sun. Several hours later, after the sun went down and the temp had dropped, I tried it again and it started right up and idled normally. Ignition module? One more thing, The first time it happened, it had rained heavy the night before. It acted like it had water in the distributor but both times the cap and rotor were dry.

Any ideas before I start tossing parts at it?

Run some tests.

duraspark troubleshooting[1].pdf

Once again this morning I have a no start issue. I started by troubleshooting the Dura spark. I wanted to see if I have power going into the Dura spark module so I unplugged the red power wire and stuck a test light in there. Sure enough I have power in both the start and run position. When I plug that back in and tried starting it again it fired right up. So possibly just a bad connection? I hate not knowing why something is working again. It makes me nervous to stray very far from home in the bronco. I've read about Dura spark module's going out when they get hot and then working again after they cool off but my problem isn't after running the vehicle for a while it's when I first start it up.


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So, I ran through the duraspark trouble shooting and it all appeared to be in working order. For good measure, i swapped out the ignition switch from a spare in my parts stash and all seemed to be OK. Drove it to work last week and had no issues until it was time to come home and had the same issue as before. It seems that the bronco does not like being left out in the sun when its hot out. Drove it again at about 6AM Sat and it was fine in the cooler temps. Sunday in the heat of the afternoon, it was hard to start and misfired for a couple blocks so i nursed it back home. I tried a new auto zone ignition box and it didn't want to start at all, swapped back to the original box and it ran like crap again ( but at least it started ) . Another trip through the parts pile and I had the original module that I had replaced in a previous trouble shooting adventure. I swapped that one in and it seems to be fine again. I read a lot on the inter web about the duraspark boxes crapping out in extreme temperatures and lots of good reviews on swapping in an MSD 6AL ignition module. As luck would have it, I own one of those. I just need to figure out what box it has been hanging out in for the last few years. I ordered the adaptor plug to merry it up with the distributor off of amazon tonight. If I can find the MSD by the time the adaptor arrives, I'll be making the swap wednesday evening.

could be 3 options. when it does this measure the resistance of the coil. Im not sure off the top of my head what it is supposed to be. When they get hot the resistance will go up. The module also can and will be affected by heat. Have also had the pickup in the distributor do the same with high heat conditions.