This problem was finally solved (after a week of trouble-shooting and head scratching). I thought I would post the problem and trouble-shooting steps for comments and info. Oh, it's a 1990 740 nonturbo with the Regina/Bendix systems and RPM sensor.

The car died on my wife a couple of weeks ago, on her way out of the neighborhood. She started it back up and drove back home to switch cars. So I drove the beast for the next week. One morning about twenty minutes from the house, it started missing as I was coming to a light. It seemed like bad gas or an injector problem. First down to three cylinders, back up to four, down to three, down to two. Better pull in somewhere. The car idled for about five minutes, unable to decide whether to curse me or not. Finally it died. And it wouldn't restart. Fuel problem right?

Tow it home. Next day it starts up and runs for about one two minutes and dies. Definitely fuel problem. I smell gas though--flooded car gas smell. Weird!
Check the diag codes for injection. No problems. Ignition system. No problems. No problems on any of the systems. Hmmm.

Pull a plug--wet. Another-also wet. Pull the coil wire off the cap. No spark! At least I'm narrowing it down. Voltage in 12v. Ground good. Harder to check the signal in without wiring up a contraption. (Heh what is the voltage of the buzzer they use to test it? 5v or 12v.) I have an RPM sensor. 168 ohms from its connector to ground (white ring). Pull the coil/power stage off and disassemble. Contacts OK. OK, I'll order an RPM sensor and a coil/power stage since they are possible culprits that can be sneaky to diagnose.

I put the RPM sensor in. Nothing. Put the coli in. Nothing. AND it's cold and raining now. No spark from the car and no spark in the head!

Well I bought an ignition ECU a couple of years ago off a wrecked car and put it in the drawer. I actually found it! Put it in and the car started right up! Heh, I though a computer that sent out the codes would work well enough to tell me that it was broken!

Maybe it's the wiring, since I moved a bunch around when pulling the ECU loose? So I plug the old one back in--no start. New one back in--starts.

Moral of the story. Never trust a computer! (I've renamed the new one HAL just to remind me.)

Any comments? Did I miss a critical step? (I know I could have put in the computer before running to the store. I really didn't mind having the extra swap out parts around.)