In your first post you said:

"I pulled the main fuel injection relay and jumpered terminals 87/2 and 30 with a manual switch. Voila! Both pumps come back to life. Attempting to start the car with the pumps on using the manual switch did not work."

Whichever LH you have (2.2 or 2.4), your jumper substituted for the Fuel relay, but powers only the pumps. It's rare that the "other relay" fails (the one that should energize at Key On), but if it does (and I've had 2 cases in my family cars), there is no power to the AMM and ECU from 87-1.

To do a complete diagnostic relay bypass, you need a 3-legged jumper having flat male terminals to plug into the relay harness socket (or rack), as follows:

Leg 1 to socket terminal 30 (heavy Red wire, fused battery +12V)
Leg 2 to socket 87-1 (AMM, ECU, RS relay, etc.
Leg 3 to socket 87-2 (Pumps)

As with other jumpering schemes, the pumps run immediately. For more than a quick test, a control switch can be wired into the leg connecting terminal 30 to the other two legs.
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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.