I posted a few days ago about how I replaced the main (FI)wiring harness on my '87 240 and how the car then ran worse--bucking, killing at stop signs, etc.

I think I found the culprit. Meter said no RPM signal coming to the ECU, so I checked and found that the ignition harness was badly rotted near the coil. I jiggled the wires connected to it and lo and behold I got the RPM signal. I think that it was shorting out somewhere inside the ignition harness.

What I learned from this:

A fault in the igntion system can disable the FI. This was confusing, because I could get it to catch with starting fluid. That made me think the ignition was OK and the FI was the problem. Well, the ignition was not OK and that killed the FI.

Igniton harnesses can go bad too. Funny, ignition harness was a bigger problem than the FI harness.

FI harness rot can be misleading. I had serious rot at all the usual places; gray plastic box on the firewall, alternator, starter solenoid wire. However after I replaced the harness, I cut the old one open, and the crumbling insulation on the ends was the *only* bad wire. Everything inside was fine. Might have been easier to just patch it.

Watch out for mixed up connectors when you do a harness. The air valve and the TPS have the same connector, and they are long enough that you could get them switched. Label the old air valve and TPS connectors before you disconnect them (these are the only connectors you really have to label IMO) and then check the wiring colors by rolling back the rubber boot that covers the end. Then make sure the wiring colors match when you connect the new harness.