Greetings Friends,

It's been a while. I took nearly two months off from my '73 Dodge Dart. In all honesty I ran out of money. I have thrown $1200 or more on the car since April and I am beyond frustrated right now. And before some of the older guys on here yell at me, my car is a rat car and far from original. I totally respect everyone on here and used a lot of information from this site in my current project. I did a total conversion from a Holley carb to a brand new Weber. Some of you may remember my original nightmares were carb related.

A friend of mine has an amazing hotrod shop and did the conversion for me. He modified the manifold to mount the Weber carb, created an amazing linkage system partially from an old rear mount Mazda truck linkage pivot that runs a small cable to the original Dodge linkage. It works amazingly and looks clean as a whistle. He also ran new fuel lines and replaced the fuel tank. I helped rip that old tank out and it was a pain in the neck. I had to cut the j-bolts off and replace it all with new hardware. My old tank had a lot of rust in it and definitely lent to my previous carb failures.

Now the carb nightmares were behind me and I thought all was going to be fine. We got the car cranked and checked the timing and got it idling well. It actually sounded like a sewing machine. I could not believe the difference the Weber carb made. But my buddy wanted to make sure everything was good so he told me to drive it around for a few minutes and then bring it back to the shop. The car drove beautifully. I was like a kid at Christmas. Two months of hassle and a load of money later and I could finally drive my old Mopar. I took it out on the highway and the car purred like a kitten. Lots of power and totally smooth.

But on the way back to the shop I stopped at a redlight and the car started idling roughly. I am talking like a big block with a massive cam. Really bad idling. The engine was clearly missing on one or more cylinders. Suddenly I was back in nightmare land with a unreliable car. So I get back up into the higher RPMs and the car smooths out. I pull back into the shop and the car returns immediately to a horrible idle.

My buddy notices and we open the hood. He thinks the problem is electrical so we break out the voltmeter and a few other tools and start checking the electrical components. We immediately discover the Mopar OEM control module is fried. It was sending out bad levels. So, I decided to replace this Mopar module and coil. We replace these components and the car idles better but still seems to be missing a little. We ran the voltmeter all of the wiring harness. Then when we checked the coil and it was only receiving 2 to 3 volts up and down. We were dumbfounded. I got frustrated and took those parts back to the store and decided to buy a $200 MSD Module and a $50 MSD Coil. At this point I was $300 in the hole. We rewired the control this time in a simple and direct way where the power goes straight from the battery to the module and then to the coil.

After we added the MSD Module and MSD coil and did the rewire, the car idled perfectly again like a sewing machine and I took it for another test drive. All was perfect again. The car drove wonderfully. Before I drove back home my friend wanted to run the voltmeter back around the wiring again to make sure everything was okay. When he got over to the coil it was registering zero!!! No voltage whatsoever! Yet, the car was running in perfect idle at this point. I turned the ignition off and started the car again on the first attempt. Again, the car is running great but no voltage reading!!! So before it was going wacky between 2 to 3 volts which is way low anyway and now nothing but the car runs great anyway.

At this point my friend who is a seasoned mechanic was burned out as was I. We had been under the hood for hours at this point. I drove the car home and it ran perfectly still. This was Saturday afternoon. I go out Sunday morning excited to take the car for a spin back to my friend's shop so he could do some more tests on the odd voltage reading and the car was totally dead. The starter turns like crazy but the engine will not fire. I checked back over all the wiring and everything looked fine. Or at least it was still in the condition that the car ran the day before. I simply cannot figure this out. My mind is totally blown. My friend was doing me a favor and does not have the time to hang on to my car and test the entire electrical system for free. He'd have to charge me hourly at this point because I already made him lose an entire shop day.

Anyone have any idea where my problems could be? Some photos of my conversion below:

I think the problem lies in your repair philosophy. Throwing hundred-dollar bills at a car problem is usually not a good substitute for careful, systematic, thorough diagnosis. You probably did have exactly the burnt-out components you discovered, but...why spend so much money on MSD stuff...? Between you and your accomplished hot-rodder guy, you could've had an ignition system at least equal to old American-made MSD, and better than current Chinese-made MSD, for $45 or so in parts. I'm not trying to rub salt in the wound here, but the problems you're having are probably down to some simple, basic part(s) of the electrical system. Corroded or otherwise faulty wire connections, bad ignition switch, high and/or spiky line voltage, that kind of thing.
I think this indicates that either your friend's voltmeter or his technique in using it is faulty.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I'm having trouble understanding why an apparent primary wiring problem was attacked with expensive ignition parts.

What was wrong with the electrical system that the coil was only receiving 2-3 volts? Are you completely certain the coil voltage was only 2-3 volts? What was done to correct this problem?

If you want to see the high voltage capacitive discharge provided to the coil you need an oscilloscope with a high voltage probe.

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Joshua

Guys, please be as gentle as you can with me. I already made the financial mistakes and now just want to make what I got work again. I am just dumbfounded over why the car ran perfectly and then went dead. It's just puzzling. My buddy used all sorts of diagnostic equipment to check the voltage levels. He has a state-of-the-art shop. But I must confess, I am an idiot with auto electronics and cannot remember every single test he ran. In the past, I was impressed when I rewired my Triumph motorcycles from a 6 volt positive ground systems to a 12 volt negative ground systems. But this was easy as pie in comparison because all I had to do was strip out all the Lucas wiring and bolt on a typanimum rectifier, an electronic advance and the Boyer control unit and I was done. Yet I am lost with the Dodge electrical system and I have a shop manual and three after market books, this great website and my friend who is honestly more into Fords and Chevys. I forgot to mention that my friend also replaced the ignition switch before the other components. So I know I have a good ignition switch, a working coil, a working control module, a brand new carb, fuel lines and fuel tank. I am just frustrated and need some diagnostic advice when considering the work I've done thus far.

The MSD has positive and negative wires to the battery, right? But are you switching it on thru the ballast resister? Maybe the resister was the first problem? The original circuit will have nothing to do with the coil anymore, aside from turning the MSD on. With a CD box you do not see constant voltage to the positive side of the coil like with points or many factory electronic ignitions.

Thanks friend. I'll take a look at the ballast resister tomorrow. But hey, can you fully explain why I might not see constant voltage to the coil in this particular application? I simply want to understand this scenario fully. I am trying to overcome my auto electronics idiocy.

There's 0 volts at the coil until the MSD fires it at about 400 volts (multiple times at low rpm)....

Probably not enough time for the voltmeter to react.

Goto the MSD site and read all about it......

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Ballast? Look at the instructions that came with the msd box, it will tell you what model coils need what ballast resistance - That looks like a msd6 box and msd2 coil - I didn't use a ballast when I ran the same setup.

I'll backup what the others have said here - you can't measure voltage on a coil hooked to a capacitive discharge box in the same manner as our stock ignitions. Thats why the MSD instructions warn you not to hookup tachometers to coil negative and hook them to its dedicated tach line - the waveform is very different.

Yep, with an MSD box you shouldn't get a voltage reading at the coil. They're a different critter from the Mopar ignition altogether.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair