rgracer11

I got a 98 Ls1 Z28 ivre been working on for a few days now. the fuel pressure regulator keeps going bad it had two whole fuel pump modules put in befor it came to me and I blocked off the return to the tank and pressures came up to normal, so I replaced the module again and pressures were fine and drove great. customer comes to pick the car up and will not start. So I had no fuel pressure again, blocked off return to tank and pressures ok and runs great. So why does it keep causeing the regulator to go bad???? I know the regulator is bad again but what is causing it to fail?