Re-posting an old thread with the solution.

Thanks to Art, Bruce, and Phil and the others for help. Porkface's comment about replacing Bosch coils more than ECUs prompted me to look at the ignition again.

In short, a new ignition coil solved the intermittent no-start. I've worked on this all summer with a 1 out of 10 successful start. I always had spark, though orange, but it'd jump a 1/4-inch gap and when it'd start, it idled okay. I swapped in a spare coil from a 940 (it doesn't fit, but I altered it to fit) and instant start. As a check, I replaced the original coil - no start. I spent a lot of time looking at fuel and everything else since I had spark - so the lesson learned is a good spark is needed. Spark in air isn't a 100% guarantee it'll spark under in-cylinder conditions.

I consider the coil as reliable as a piece of wire and its resistance always measured correctly, but in my case, it was the problem. I hope this helps the next trouble-shooter.

P.S. the pin sleeves on a Chrysler-Volvo ignition (1986) module are about the same size as standard brass tubing from a hobby shop. I used this to augment pins 1 and 10 to insure proper coil contacts.

TM