GMC Repair: new fuel pump, new fuel relay, no fuel, oil pressure switch, bosch pump

Question
1994 chevy k1500 5.7 truck died, replaced fuel relay, banged on tank ,and it started ,shut off ,no start replaced fuel pump in tank,another fuel relay installed,while tank was out I noticed the ground wire -to the frame- from the tank ,kept comming loose as I tried to reinstall tank,moved ground wire to another spot on frame, resecured ground ,reinstalled tank w new bosch pump,no start,removed ground wire scraped rust to metal reinstalled,started right up--
ran fine drove it 14 miles on and off  5 or 6 times and it quit on a real bumpy road ,rented code reader obd1 stored code said faulty fuel pump relay,installed 3rd relay cleaned and checked ground,still dead ...,is there another relay or cut off?,I have been checking all fuses too, no power to tank, power to one wire at relay,---
and what would cause the power to the relay to switch places ,while testing for power once the power at relay [relay removed] was at black wire, then later it was power to orange wire, than it went back to power to black wire,yes I ve gone over the wires and nothing obvious?

Answer
Hi
The PCM controls the fuel pump on the green/white wire.
It should get hot KOEO. The orange wire, obviously hot all times.
The black/white should be ground al times.
Red is DLC prime.
The gray GOES to the Fuel pump fuse, (right next to relay) IT also goes to the Oil pressure switch AND the PCM AND the fuel pump.
IF you have checked all the wires, fusable links, and connectors as stated, I would suspect either the Oil pressure switch or the PCM.
Good Luck
Pawl