I have a 1970 Challenger, 440 4-spd with electronic ignition. I’m pretty sure it used to be points and was updated by the former owner.

The problem I’m having is that while I’m driving down the road the engine will stall abruptly. This happens at idle, and also under throttle. I’ve had it at about 1/3 throttle and watched it stall. When it stalls I steer to the side of the road and usually it starts up after about a minute, sometimes right away. It's a very quick stall - it doesn't chug or stutter beforehand. The car is running great, and then all of a sudden the rpm's are 0.

I’m a shadetree mechanic but certainly no expert.

At first I thought fuel delivery. I adjusted the carb and replaced the fuel filter and fuel pump. No change.

Then I thought ignition, and replaced the coil. No change.

Now I’m wondering if the ballast resistor is going bad, and if the ballast resistor is even the correct one. Here’s a picture of the firewall ballast resistor. Shouldn’t it have 4 connectors for the electronic ignition?

Thanks.

Jim

I see you have the dreaded orange ecm. You might want to go to a stock one.

Oh, I hadn't heard about the orange ECM. Problematic?

Seems to be from all the posts about them here.

The newer ones made in the past 15 or so years, yes.


There was this topic recently that talks about new(er) ECU's and their issues. The orange box is mentioned in there too. ECU LINKY

I'm thinking dist pickup coil/ECU or maybe a loose connection which might be a bear to track down. You are fine on the 2 terminal ballast. Your parts house has 4 terminal ECU's for cheap. I dont like to shotgun parts at a problem but carrying a spare ECU is always a good idea (if it turns out that ain't it) if you cant borrow one to do a check. Nothing was changed right prior to this happening?

Forgot to mention, make sure the ECU has a GOOD ground. Is there paint under those screws? On my cars where I can access the back, I'll use a nut and bolt rather than rely on self tapping screws. I'll also run a ground strap from the mount to the block too.

I'll check the ground on the ECU (as well as the other firewall mounted stuff) to make sure.

This is a new car (for me). I just got it in November '18. Nothing at all has changed since I got it, other than the recent parts swapping I did (fuel pump, coil). The drive train and engine compartment were rebuilt & refurbished by a prior owner and there's only about 2K miles on it since.

Thanks.

Oh, only other thing I can add is that when I had the car running I starting wiggling wires to see if any would cause the motor to stall. None caused a stall, but when I wiggled the passenger-side connector on the ballast resistor, it sparked. Not sure if that's normal!

Not normal. check/tighten the female connector or if it is the ballast windings/one of the terminals, replace it

Your ignition feeds through the bulkhead connector on the way to the ballast resistor. It’s not a very reliable connection after 50 years. Check the connector and clean up the connection. A fair amount of current passes through, and it’s often a poor connection. It will kill your ignition in a heartbeat.

Ballast resistor. Just replace it & see if the problem is solved. Same exact thing happened to me before.

This.

I fussed around on one of my cars because some Meathead used a wood screw to attach it to the firewall. After that it would cut out at WFO. Scuffed and re-attached and has been good.

Many years ago, a buddy with a '70 GTX had a similar problem going on. 440+6, 727. Car was stock and a few years old.
Driving along, the engine would just quit. Always restarted after a few minutes.
Poking around, it turned out that the distributor wire had a bare spot that would ground and cut the ignition.

A few intermittent's we've found:

One of the wires to the pickup inside the Distributor was broken internally, likely from the vacuum advance movement.

The 12V female connector for the control box was set too deep in the molding barely making contact. It would die when the R door was closed too hard, LOL

Bad Coil wire in the cap, arced it's way to a burnt up mess

And last, A mopar conversion kit wired to the wrong side of the ballast limiting the V to the control box.

keep us posted

I was under the hood today trying to figure this problem out, and I took a closeup of the ballast resistor connections. Does this look kosher? Looking through wiring diagrams online it appeared that a red and blue on one side required the 4-connector resistor.

Pic attached.

Is anyone familiar with that?

Thanks.

FYI - The ECU is a 4-pin.

the blue wire on the blue/brown pair should go to the coil positive primary terminal & I'm assuming the brown wire is ign2 "cranking". On the near side terminal (ign1 "run" voltage) the blue wire is the ign1 (run) circuit & the red wire likely goes to the ECU "power in" terminal at the ECU pentastar connector. If the pentastar plugin connector is OE, that power in wire would originally be red and it would be blue/yellow if this is an MP add on electronic conversion kit (which I am assuming it is) with the pigtails & the orange or chrome ECU both of which are 4 pinners. Holler back.

I assume you checked under the cap, my car died suddenly and found the rotor had shed all it's metal parts and this. The pin the plate rides on had sheared and the pickup said hello to the reluctor. not sure if they happened at the same time.

So here's today's update:

I checked the firewall bolts and they all look properly grounded. I back ordered a new ballast resistor which gets here in a few days.

Then I swapped out the orange ECU for a chrome one that I have on my 71 Satellite and took the Challenger for a test drive. It drove very well. The idle was very consistent and actually ran about 150 higher rpm's than it had been. I drove it about 3 miles which was further than I was able to get it without stalling. Then I brought it home, swapped the orange ECU back in and drove it some more, hoping I'd see a difference. Unfortunately it still didn't stall, but the idle was a little lower and at times slightly inconsistent. Could that be enough of a clue to pinpoint that it's the orange box? This intermittent problem is driving me nuts.