Oldsmobile/Buick Repair: sending unit, fuel tank sending unit, oil pressure sender

Question
Good morning Van,
         I've been working on a 92 Olds 88. I changed the fuel tank, sending unit and pump. I went to plug it back in and lost the signal for the grey lead ( the pump itself ). The fuel guage has good power, the ground is still good but no pump power. Any idea where this signal is generated? (i dont have a shop manual)

                         Thanks in advance...
                                   Gordon

Answer
Hello Gordon,
That power for the pump comes from the fuel pump relay, which the ECM activates for about three seconds after the key is turned on, and then turns it off, unless the ECM is getting a crank signal, meaning the engine is actuallo turning. Then it is on all the time the engine is turning.
As a backup system, there is a switch in the oil pressure sender that sends power directly to the fuel pump as long as oil pressure is above about 5 psi. But then again, the engine must be running, or at least cranking over with the starter.
There is a fuse for the pump also, which is a different fuse from the gauge sender power.
Listen back there as the key is turned on, and then check the fuse. If it is blown, see if maybe you pinched the wire when bolting the tank in.
Van