[BR3W CITY]

Sounds like either a pump voltage issue, or a restriction issue on the filter or line somewhere, causing the pump to lose output after a few minutes.

You can also try putting a multimeter on the power wire to the pump, and watching the voltage as the FP drops. If voltage stays consistent, then the pressure issue is coming further up the line (FPR, fitting coming loose). If the current drops, then it could be a grounding or power source issue. If the current goes UP, then a restriction is causing the pump to pull more juice to run as normal, and it can/will do so until it blow a fuse, cuts out, or just heats itself and locks (depending on the pump).

I have no clue what pump rock valley gives you, but if you can find the spec's on it we can figure out a little more. If the pump isn't setup for high pressure, or just doesn't move enough fuel, that has to be addressed.