Weak spark, Mopar ignition box.;UPDATE

I have tried two different ballasts, last one is 1.5 ohms, two coils, and I have another new one to try tomorrow. The box has been changed to a new orange box, and that helped for a while but then the problem came back. I have also changed the ignition switch. The spark gets weaker as the car runs and gets warmed up. Once heat soaked it has so little voltage it can hardly be seen, and starts to cut out and then the motor dies. This is a whole new wiring system, and a new ignition switch. It is a universal type, not a replacement system. Any ideas on what the heck is going on?

the dist pickup might be acting up when it gets hot. Ohm it when hot & see if it will generate ~1V AC. seperate the zigzag connector & check it ASAP when good & hot. I'm assuming the gap is OK (.008") & rotor phasing is acceptable (RP wouldn't cause this by itself but might aggravate this if it is borderline). Might be (2) orange boxes in a row. This is a strange one! We will solve it

RR, I will test that as best I can, I also bought a new one of those pickups to change out.I am thinking weak ground, high resistance/bad connection in the circuit from the ignition switch, although this is a new system, freshly wired. Any more ideas will be appreciated
I hope I have some hair left when I find the problem This issue has been clouded by two bad carburators , which I finally got under control. The car then ran like a scalded cat for ONE DAY! An MSD box is starting to look good!
This is in my street 65 Dart, 318 auto.

Sounds more like a ignition coil failure to me. The box only controls current to the primary winding's of the ignition coil on or off. That timing is controlled by seeing the signal from the distributor pick-up at various rpm. I doubt if it would fade with, more likely with RPM change. If the ignition coil is getting proper voltage I'd swap the coil. Coils are susceptible to heat failure.
Doug

(1) yes sell it to me (2) I agree with Doug it does sound more like classic coil failure, acting up when hot but I thought otherwise since you had replaced it.

I have every part of the system to swap out now, so I will find it! I will post results (or beg for help!)as soon as I get time to work on it.

X3 classic coil failure symptoms.
Pickup coils usually work or they don't. Ignition box nope, it happened with two different boxes.

R.

Any ideas on what the heck is going on?



Check the voltage across the coil with the key in the "run" position when cold and you're getting a good spark. Check it again when it's weak and the motor dies. If the voltage is the same then the problem is for sure one of the ignition parts or a bad ground. Remember the ignition box case has to be grounded to the firewall or other good ground. Same for the frame/firewall to engine ground strap. Check the ignition box case to the engine with an ohm meter, you should see .4 ohms or less.

Coil , and get that POS orange box out of there ...

A different Coil didn't fix it, but the old one may have fried another box. It was a chrome one designed for the gold box system, and can draw a lot of juice. I had a 1.5 ohm ballast on it. That was the second coil used in trying to fix this thing.
I spent the afternoon building a test system on the bench to find out which parts were good and not so good. The outcome was two burnt boxes, one a new Summit Blue box, (same as mopar orange), the other is an unknown that came with the car. The third one came from Autozone, and works well. I found a few threads on other forums that talked about some coils over loading these boxes, especially if the resister/ballast is too low of an ohms reading which then puts too much juice through the box, hurting it.
The end result is I don't trust the system, as it ran great for about ten miles, then started to break up the last time it died. The Summit box didn't totally quit, but the spark was so weak it wouldn't fire the cylinders under virtually any load. I really don't want to get stranded again, and might just buy an MSD and call it a day!!

I ran a new ground and new 12+ directly from the battery to the control unit as a test, and had cleaned the battery to frame and battery to motor grounds. All read what I thought was good with an ohm meter, but will recheck the box to motor for .4 or less ohms.

It turns out that of the three boxes I tried, only one got fried, the blue one from summit. I also could have done that with my test setup and the high output coil. So the end result is, I still have no idea why the spark was weak with the other boxes. I could make it work fine on the bench, but not in the car. I checked all the grounds, hot leads, no problems, or at least nun uncovered. The ignition switch was changed, ballasts changed, hot lead for the ignition switch comes directly off the starter solenoid to the new Quickwire fuse box. The end result of all the testing and replacement was I still had a spark that wouldn't jump a gap bigger than 1/4 inch at the plugs, tested on a couple of plug wires and also off the coil wire. I got it to run, but don't trust it. One thing I haven't mentioned that might be an issue is the old ignition module was mounted on an aluminum plate under the dash, which was grounded to the firewall with a 1/4 inch bolt. I didn't see any resistance with the ohm meter though.
Due to this being a street car and I need to trust it, I installed an MSD streetfire. Ordered it from Pep Boys online, got 25 percent off the 149.50 they ask in the store, and picked it up at the store. total cost for piece of mind, $120 with tax.

I've seen this problem before. In my case the distributor pick-up gap was too large. As Rapid Robert suggested, check the pick-up gap with a non-inductive gauge at .008.

& I sure wish you had another dizzy or at least a pickup/plate assy you could toss in for a 1 hour test. If it IS that it's gonna act up when the MSD gets in there (unless the kit has a dist included)

New MSD works fine so far, new coil was tried as a last resort with the old system. I do have a new distributor pickup, in the trunk with tools!
I didn't change that out, as most said, it ought to work or not work. The symptoms were weak spark, and I could change how bad it was with a resister and or a module change. Thanks to all that contributed If it acts up again, I will update.

The problem will return The problem is probably the ground or in the dash harness / switch wiring One suggestion you should have out in a pertronix they either go bad or run and I have never had one that went bad in years

John,not all orange boxes are a POS !!