Engine died while crossing RR tracks

['74 Sport]

Many of you may recall that my son Aaron and I have been rebuilding his 74 Dart Sport over the past three years after it was totalled his last year in college. We swapped in a 360 for the original slant six and kept all the old wiring harnesses. For the past couple of months, while doing all the last few things to get it road ready, we have been driving it a bit around locally, and it has been running great. We finally drove it to town last week (about 20 miles round trip through town with plenty of stops) and had no hint of trouble. Monday, I drove it to a meeting about two miles from home to show it off. After the meeting, it started fine as usual, idled perfectly, and had crisp throttle response, for about 10 minutes of oohs and aaahs. On the way home, I took my sweet time toodling through the two stop lights in town and eased over the RR tracks. As I started to come off the back side of the tracks, the engine died instantly. No stumble, no stutter, no hesitation first - just dead as a hammer, like I had turned off the key. I rolled into a parking lot and that was it. Holley 750 was getting plenty of fuel at 7 psi, Chrysler mini starter was cranking strong, and there were no apparent wires melted by the headers. Nothing I did would get it started again, so a tow from the wife was in order. Got it home and pushed it back in the garage where it sat untouched until last night. On a lark, I thought I would give it a try and it popped right off, first turn of the key! :wack:

I am bummed out in a major way. My 40th high school reunion is tomorrow evening and I was looking forward to driving the Dart there. Now I have absolutely no confidence that I'd either get there or make it back home.

A few things I checked last night:
Battery
12.68V off
13.54V running
12.70V running w/ lights on
Ballast resistor
2.2 ohm primary
6.1 ohm secondary
ECU pin 5 has continuity to ground
ECU has extra ground wire case to fender

Any ideas are certainly welcome. Let the games begin.

 

[TrailBeast]

Make sure the distributor plug is clean and tight.
I have had more than one car do that because that plug expanding and contracting from the intermittent hot and cold.
One would start every morning like clockwork, then die after running and not start till it cooled down again.
The other one was exactly the opposite (started fine later in the day when it was warmer under the hood but not first thing in the morning)

It was that connector on both of them.

 

[GMachineDartGT]

Look for a bad connection starting at the white plug under the dash for the ignition switch. Put a test light on the positive side of the coil where you can see it lit. Turn the key on and start checking the bulkhead as well. Sounds like a bad connection cost you 12v to the coil while running.

 

[67Dart273]

The distributor connector is a "good place" for trouble, because there is almost no current flow there. It can corrode.

Wiggle and work all the ignition connectors in and out several times. Distributor, ECU, ballast.

It would have been better if you had tried to fix it "right then" so to speak, but I realize...........

Also I believe these cars had a big WHITE connector under the hood, connecting the engine harness to the firewall section of the harness. These are subject to failures.

One test you can do "when fails" is to leave the key in "run," remove the distributor connector, and tap the bare end of the 2 pin firewall side of that connector to ground. Each tap should generate one spark. If so, might be the distributor or that connector.

If not, ECU problem or other wiring connections. Make absolutely certain ECU is grounded

Coil + should have something around 5--9V with key "in run." Below 5 indicates a voltage drop problem, nothing a wiring problem or bad ballast, 12V is ECU problem or ungrounded, or bad coil.

Under same conditions, coil NEG should have low voltage, perhaps 1V. Nothing at all is a problem, 12V means the ECU is not causing the coil to conduct or ECU is not grounded.

 

[RedFish]

I'll throw my best guess ... Jounced carb flooded the engine. After the plugs dried it seems fixed. Double check bowl float level.

 

[jimjimjimmy]

if this happens again give the bulkhead a wiggle if all else mentioned here fails .