So here's a weird problem... I have a 1991 with the 6g72. It has voltage at the fuel pump in the "start" position, but not the "on" position. The guy I bought it from couldn't figure it out either but he replaced the following:

Computer
Engine Control Unit
MPI Control Relay
Distributor
Coil
Throttle Position Sensor
Air Idle Control
Fuel filter

After I bought it I replaced the following:

Mass air flow
Fuel pump

I ran a jumper from the battery to the fuel pump check terminal and it runs fine.

What would cause the fuel pump to shut down?

It may also be relevant to mention the heater blower motor, blinkers, hazards, and brake lights do not work.