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I believe the lack of power to #4 tells me the computer is not putting out.
Fuse #4 gets powered by the Fuel relay, which gets energized by the ECU completing the relay coil's ground path.
But the ECU won't energize the Fuel relay unless/until it gets timing pulses from the Ignition CU—ergo, Spark trumps Fuel.
That said, my prime supect would be the 25A blade fuse near the coil, which feeds the whole FI system. I too like the 4-6 jumper test, but it completely bypasses that 25A fuse and the fuel relay. The fact that you tried another relay fuels (couldn't resist) my suspicion of that 25A fuse, the fuse holder, and the holder wires—especially at the Battery + terminal, where corrosion may be more prevalent (take a close look there).
The FI ECU would be dead last on my list.
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Bruce Young '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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