Crank, crank, tries to start as the key is released.

[ckessel]

Greg, see how much voltage you have at the positive side of the coil when the switch is at start and run. You may have too much voltage drop by the time it gets there.

 

[Jeff Erwin]

I had this EXACT issue with my 440x6 after replacing the entire wiring harness. I also replaced the alternator with a single-wire as required my the American Wire harness, and replaced the distributor.

The spit-up when you turn the key off is due to a single spark getting through as you turn it off. In my case I had replaced the MSD distributor with a new MSD distributor that had the ECU built-in so the stock ECU was redundant and making everything not work. A call to MSD straightened this out and the engine fired right up.

You didn't mention if you had replaced the distributor. Simple test, if you pull the distributor while still wired up and spin it manually, do you get a spark from the coil? If not, and if you replaced the distributor, might be a simple wiring issue because of redundant ECUs

 

[Ron H]

Having a similar issue where vibration from driving or even closing the hood had me stopped, it drilled down to a bad connection at the BH (ignition wire in my case). In my situation, 95% of the time the culprit is either a bad ballast or key switch (those checked fine). I had a new engine harness in after this happened. The harness would slightly droop, not visible; but pushing it in got me going. Noticed evidence of overheating at the BH connection. I had been putting off installing a new BH despite it being skanky; but this finally forced me to say enough and put a new one in. But damn, after this encountered the same thing again, just less often. With further checking, the poor connection also caused overheating inside the new harness creating a loose contact. Slipped that wire out and put in a new connector and all has been fine since.

 

[Jeff Erwin]

The American Autowire harness also eliminated the alternator gauge so no more full current flowing through the bulkhead connection. There are simple ways to get the altmeter back online without going through the BH connector.

 

[Vinny]

Have you checked the neutral safety switch?

GRABBER, if the problem was the neutral safety switch, the engine would not even crank.

 

[Crackedback]

If it cranks and doesn't start until key is released, check the wires passing through bulkhead IGN 1 and Ign 2 circuits. The brown wire on a couple of my cars didn't want to play nice in that area.

 

[RemCharger]

It's when your 440 starts running backwards and pushing exhaust through your snorkels that'll really get your attention!
I'm pretty sure it was the ecu for me, but that was 20+ yrs ago.