"3. I tried turning the key on & off - no fuel pump noise & no clicks from relay (holding it in my hand)."
• That's a good test. The System relay so seldom fails, it's often overlooked. But you wont forget it now. Along with the AMM and ECU, etc., it also powers the Fuel relay coil, which the ECU grounds when it gets timing pulses from the Ignition.

"re your 'This will power both pumps, and completely bypasses the 25A fuse as well as the Fuel "pump" relay'. I thought that jumpering only this only made the pump run but did not activate the ECU (You have to use a 3-wire jumper at the relay to do this)"
• Yes, I slipped when I said "completely". Nice catch. As I said above, the System/Main relay is hardly ever the problem, as reported here (although I've seen it on two family '87s). I guess maybe you saw my "Y" jumper post?

"a. I'll try to clean/ replace the injectors. "
• Before that, I'd suggest removing and cleaning the 3 ground points on the intake—2 on the injector rail brackets and 1 on the pulley bracket. I don't know off hand which is which, but those are the main AMM, ECU, and Ignition CU grounds,

"Note: I don't have a fuel gauge so it is possible that I've got a clogged fuel filter and my visible test of fuel pressure is misleading ie. I don't have enogh pressure for the ECU to activaste the injectors."
• I guess the filter could be suspect, especially if it's of unknown age/mileage. But I'd get a pressure check before digging into what can be traumatic the first time. I've never personally had or know of a verified "clogged" filter.

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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.