The fuel pump relay wiring described above seems odd to me.

Typically, the fuel pump wiring high side gets battery+ from a wire with an inline fusible link or a fuse that eventually is connected to the Battery + terminal.

The computer supplies a battery + signal to the fuel pump relay low side, with the other low side terminal connected to ground. When the fuel pump relay high side contacts close Battery + is sent to the fuel pump.

Typically, the oil pressure switch wiring gets battery+ from a wire with an inline fusible link or a fuse that eventually is connected to the Battery + terminal.

Typically 5 PSI of oil pressure closes the oil pressure switch to send Battery + to the fuel pump.

Typically the oil pressure switch fuel pump wire and fuel pump relay fuel pump wire are spliced together so either the fuel pump relay and / or oil pressure switch will supply Battery + to the fuel pump.

Typically ECM Terminal B2 is spliced into the wire that sends Battery + to the fuel pump.

Possibly the wiring diagram shown below is helpful.

Fuel Pump Relay.JPG