I checked the Control Relay. Opened it up and its pristine inside. Looks brand new. I manually operated the relay contacts and confirmed good continuity. I think its fine.

So now I think its the ECU. I rechecked it and its giving a replace code now. I've replaced all the e'lytic caps already and I don't see anything else on it that looks suspicious. If I get a chance today (have to work) I'll check for spark at the plugs again. Should be no spark now I suppose...

Anyone local (or not) have a spare '91 ECU that I could buy or rent? Once I know that's the real problem I'll spring for an AV-Pro rebuild.

This would potentially be the 2nd ECU failure for this truck. Should I be looking at the ISC as well? I think I read soomewhere a bad ISC can kill an ECU.