Hi this is MATT. The pressure sensor should not affect the fuel pump operation. You say you can power the pump directly, so that means that your ground is good. But you should be able to power it from the red prime connector. I'll include a diagram, but the prime conn. goes to the fuel pump relay and then to the pump. So try to power the pump from the relay. Then you will have to check the signal from the PCM to the fuel relay. It sounds like everything is working for a few, but then what? Do you loose the PCM to relay power (to close the relay)? let me know, MATT
Use the wire colors to identify the relay. dark green/ white, blk/wht, org, red, and grey. The diagram should help, With the relay removed, you should have a ground on the grey wire. This will prove that the pump is grounded. MATT
Okay, check the black wire coming from the fuel pump at the tank for a ground. MATT
It should bolt to an eyelet at the crossmember.