Log In failed when posting above, so I couldn't edit this in...

The buzzing you hear is the rapid pick-drip-pick cycling of the relay.

What I said above is basically true, but shouldn't happen (at Key position II) on an '88...
"The fuel pump relay is buzzing when the key is turned to the on position, when the dash warning lights illuminate, before trying to turn the engine over"

With your LH2.2 FI there should ne no power to the relay until engine is cranked (or running), as Rhaire said below. The relay is controlled by the ECU, which requires timing pulses from the Ignition controller before it allows the Fuel relay to energize.

That said, it seems like the pumps should have run when you manually closed the contacts. I don't see anything in the normal circuit to prevent that.

But maybe we don't have normal circuits? Because earlier you said you "bypassed the engine temperature control" then later that you replaced a BLUE temp sensor with a WHITE one from a '93. Both of which raise questions to me. (1) the sensor "bypass" and (2) what effect the possibly wrong sensor might have.

Was that the 2-wire ECT sensor way back under the #3 intake runner? If so, that's wrong because the post '88 ECT sensor is not (electrically) interchangeable with the earlier one. And the '93 ECT is BLACK, not white. So the mystery deepens.

I guess I'd try swapping out the relay in any case, since manually closing it should have powered the pumps (given a good 25A fuse circuit).
Why it buzzed at Key position II is still a mystery.


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