I picked up a 440 U code '70 Challenger. Was restored something like 15 years, had about 37 miles put on it over the last 10. The car was a "reference" restoration back in the day, with a powertrain by Frank Badalson, etc. Totally stock, even uses the solenoids on the carter carb and the points distributor. The coil is stock. Everything is showroom stock. Really nice car.

Anyway, I had a few things to fix (water pump leaked, brake booster solidified, and so on) and have reached the test and tune phase. First driving session, ran really great, loads of power, just a few non-motor tweaks and some timing hit or miss adjustments. Second day, took it out again, ran really well until the problem started. The "lots of power" started to seem a little less, very subtle, seemed to be a slight miss in certain circumstances. Drove it some more and the slight miss became a very pronounced miss from the exhaust, not quite a backfire. I head back home with it and it stalls as I pull in to my side street. Starts right back up, goes down the street and stalls again as I pull in to my driveway, sort of missing the whole time. Get it started again, very easily, almost get to the garage where it stalls again, this time it won't start.

OK, new day, trying to figure what is wrong with it. Here is what I know...has a 1/2 tank of fresh gas (race and today's premium mixed). Plenty of gas shooting down the carb throat when the pedal is pressed. The easilycranks easily, no strange noises, Pulled a plug wire, checked with a spark tester to ground, no spark when cranking. Pulled the coil to distributor wire, no spark when trying to crank it, holding it near the exhaust manifold. In my pile of parts I had a coil and ballast and swapped both with no change. When the ignition key is in run position, the carb solenoid normally extends like it should, until now when it does not. The distributor solenoid is making a buzzing noise when the key is in run position, but I had an extra solenoid which got rid of the buzz but made no difference on the problem or the carb solenoid not extending all of the sudden. It did have the radio noise suppressor, I disconnected it in case it was a short.

So any ideas? I replaced then positive battery harness as I freshened up the car, the rest of the harness are as I got it. The engine harness seems to be not original, stock appearing, but sort of loosely wrapped which makes me wonder if someone had been in it. Everything under the dash is clean, unmolested, looks original. I have a Sun Distributor machine, before taking the car out I swapped cap, rotor, points and condenser, Dwell was a solid 30 degrees. Cap and rotor are NOS.

Check the wiring connection at the bulkhead. Down by the steering column at the firewall. Remove it and clean the contacts. Then try again. If it starts now you want to really clean it up cause you’ve found the problem. The ignition feed on that terminal block carries a fair amount of current and is susceptible to failure over the years.

Ditto the above, and once validated, start checking for voltage at the ballast, then the coil, and up the line.

Check the points gap and make sure the condenser is tight.

All the above.

But a quick check is to see if you have 9 Volts at the coil Positive lug on run and 12 volt on start.

Thanks for input. I had not yet checked the connectors coming off the column, though very possible that I disturbed something as I was putting the booster back in (I am 6’5”, 240...I pretty much accidentally disturb stuff all the time!).

I did check voltage across the coil. Getting 9 volts when checking positive coil terminal to engine block while car is turning over with the starter. Can’t check run as it won’t start. Swapped Ballast Resistors and got the same reading. Getting about 8 volts from one side of the coil to the other when trying to start the car

Usually all the grounds are bad on anything perfectly painted and restored to the Nth degree.
Sometimes Folks are shy about sanding off that perfect paint to create good grounds.
I'd definitely look there.

Look at resistance from engine ground to battery negative.
I'd check for 6 to 9 volts at coil + in "run", 12+/battery voltage in start.
Check coil primary and secondary resistance, also check continuity from the case
to the windings as any sort of a circuit found there constitutes a shorted coil winding.

You check run by turning the key on but not going into start. That is the voltage in the run circuit.

Sorry on the run...mental lapse.

So on start still just a bit over 9 volt. On run, 7.8 volts.

I already took the ground cable off the block earlier today, chased bolt and threaded holes, all paint off the manifold and cable in the contact area. Show 0 loss from battery to manifold bolt.. Radiator support ground is clean as well.

I have three coils I can swap with. I started with a resto coil at 1.9 ohms primary and 10.1K ohms secondary, The one in there now from this morning is 1.5 primary and 9.8 secondary...it is the one that came with the car, looks like an old NOS unit, I just swapped it back in. The third is a resto that I haven’t yet done anything with and is 1.8 primary and 10.1 secondary.

Have you checked the points and condenser yet? Also look at the under side of the rotor where it fits over the distributor shaft to see if it burnt through and the center post of the distributer cap. I have seen that before.

Weird stuff now... I am getting zero voltage with the key on to the carb idle solenoid. Connector to meter to negative ground. But, I am getting 13.1V from the connector to the positive battery cable if the key is on or off...means I have a short somewhere or just worthless data?

if you lost the idle solenoid power feed, its lost its ignition run feed. Check the dark blue wire coming out of the bulk head. Unplug the engine harness from the bulkhead and look at the terminals. If they're good follow back to the ignition switch.
Doug

Checking dwell while cranking will tell whether the problem is the coil or distributor. I'm guessing bad connection at the bulkhead (really common on cars that mostly sit) or the points.

Check the wire between the points and coil for continuity or grounding as well.

Great input. I will have a chance to take a further look this afternoon. More soon

please let us know the outcome.

Took a look at the harnesses. Didn’t have to go very far. The bulkhead connector slot mating with the engine harness terminal going to the alternator main terminal (heavier gage black wire) is melted. Looks like it happened a while ago and someone took a new engine harness and just went for it plugging it in. Sort of remarkable there was a connection there at all, the bulkhead is distorted a bit, small chunks of plastic are missing, the bulkhead terminal is corroded.

As coincidence...I had noticed as I took it apart a few weeks back that the spot for the coil high tension cable on the distributor cap was burnt, I thought it was strange that someone would use that cap and I simply went ahead and replaced it. So who knows what happened and how it was set up before.

The heavy gage red wire coming out of the column as part of that ignitions switch harness is clean, but the plug looks like it also had been melted a bit at one time and someone cleaned up the hole with a drill and a file before putting the terminal back in. There are also a couple of splices in the cables coming from the ignition switch, to the smaller gage red wires. The harness connector connection was just probably “OK” for that wire.

So I just stopped there. Have some work to do replacing a few things before trying the whole thing again. I also am going to (gasp) switch it over to electronic ignition while I am at it. I have had solid performance across a dozen or so cars from the Mopar ECU’s, and now the JEGS blue ECU (still have some old made in America Mopar units as well). I know points work great, but I have an electronic distributor all set up and ready to go that I had been keeping for a while with a nice curve and solid performance, time to use it. Plenty of time to work on the car, can’t go anywhere with all that is going on, no car shows or cruises for a bit.

Thanks to all!!

You can get bulkhead connectors off Ebay but they are for 14 gauge and smaller. I have crimped a 10 gauge wire in one and then soldered it just to make sure.

https://www.ebay.com/itm/Mopar-Male-Female-14-16-AWG-Gauge-Wiring-Harness-Terminal-Crimp-Connectors-NOS/192502001151?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

You may want to investigate the dash harness as well. I had a similar case with a 70 B body car I purchased that the engine harness burned up on and was replaced. Car ran fine, though while I was under dash working on some other issues noticed same wire damage. I had to unwrap a significant portion finding much of the ignition wire damaged, including bulkhead connector. Some extreme length of factory wire spot welded to run to other items, contributed to the damage. In the end, I shorted the ignition wire up and double connected to get to the other items. Get some cloth tape for rewrapping harness.

Under the dash I can see a couple of splices. Going to have to decide how to proceed on this. Could just replace the bulkhead connector and check each terminal as I go and repair where needed, or go for replacing the under dash harness. I normally work on B-Bodies where there is room to work, not sure how easy this will be on an E-Body.

I also noticed the run position on the key is sloppy, several degrees of slop on the return from the start position. Given the sloppy connector and splices in the harness I will replace the starter switch in the column.

I don’t mind all the harness work, but it is less fun to be sure!

Overall this is a really, really, nice car inside, underneath and throughout. But it was restored twenty years ago, and driven 37 miles since 2012. It has been amazing how the rubber suspension parts have turned to soft goo, etc. New tires, various new suspension parts including the leaf springs which were original and had taken a pretty lazy set (I used Eaton Spring with a +1 inch setting, came out great, swapped the part number stamp leafs). The water pump seal was practically none existent, the radiator hoses were both leaking. The brake booster had turned to granite, MC leaked internally. Has been unusual getting this back to being a reliable ride, though fun. I drove it more in test this past weekend, about 40 miles, than miles it saw in a decade....knowing that I would have a new list of things to do when done. Well, I certainly got it.