Let’s say you, or someone, accidentally mixed up the fuel send and return lines while replacing the hoses, and tried to start the car a few times before you, I mean they, had realized what they’d done. Then let’s say that car began experiencing a number of issues, like erratic and inconsistent fuel pressure and vacuum readings, to the point that it no longer ran.

Do you think maybe that fuel hose mixup wrecked the FPR? My understanding of the part’s guts is that there’s a check valve that actually regulates the flow of fuel back to the tank and thus maintains consistent fuel pressure, but gets opened more or less by a spring/diaphragm that’s actuated by vacuum depending on injector duration/ignition. So it’s not as if the reverse flow would LIKELY put undue stress on the diaphragm. It’s confirmed there’s no fuel leaking from the vacuum port. However, could the valve have been damaged or weakened? And that sometimes it works and sometimes it doesn’t? Fuel pump is brand new, no hose leaks, no injector leaks. My friend isn’t sure what else it could be.