Car kills all of a sudden - 1973 Dodge Charger

[elanmars]

Ok, so this gremlin just popped up and I figured I'd ask you folks if maybe it's happened to you, or rings a bell.

Anyway-twice, I have been driving along, and the car will shut off. The car still has power lights/radio etc, but won't crank-I just get the starter whine, and because I was in the middle of traffic both times, I didn't have enough time to do trial and error to pinpoint what it was I pushed/jiggled to make it work again-I popped the hood, and I jiggled/pushed the ballast resistor, and other wall-components, and voila car cranks right up and keeps driving a-ok.

Could be a loose wire somewhere? Some other kind of electrical issue? Anything else?

[will]

I have had that problem of it not starting in the past. Starter relay, jiggled and started. Maybe start there by looking for loose connections. Electrical connections have to be tight or you will have problems.

[Just 6T9 CHGR]

Check the bulkhead connector on the firewall for loose/corroded connections...

[Nacho-RT74]

ok, lets see... no spark or no crank ?... sorry couldn't tell on the post

if no spark... it can be ANYTHING, from ign switch up to coil and ECU.

Voltage and ohms checkings:

on RUN... around 7-9 volts ( sometimes less depening on ballast temp ) at + lead of coil and 11-12 volts to blue wire at ballast.
While cranking, just right the opposite.

on RUN... the ECU must be getting also 11-12 volts and blue traced yellow wire

with ECU disconected, the wires running to dist must read 150 to 900 ohms ( I have found 280-290 ohms on most of them ). I tell to check on ECU plug, because you'll be checking at the same time the pickup coil and dist plug on that test.

one of the Dist wires pins on ECU must get continuity with chassis ground ( can't recall which one )

Bulkhead conectors is something to check after all these years as mentioned by Chris

[ODZKing]

I had a similar issue with my 67 that I had converted to EI. If you've done the conversion here is what I suggest.
Everyone said that the ECU will work or not, but mine was intermittent. Embarrassing after you call a tow truck and when he gets there HE turns the key and it starts. 
Anyway, one day it finally died so I could trace the issue. The ECU's are inexpensive enough, so I keep and extra in my trunk.
Just a suggestion but as Nacho pointed out, it does sound like an ECU related issue.

[Bronzedodge]

I had a similar problem after replacing my negative battery cable with some crappy repo.  Check your grounds.