What 383man said. I run an electric fuel pump, when I put the repro vapor separator on, I turned the pump on to check for leaks, I could hear fuel flowing like crazy, turned out there was no orifice in the separator and most of the fuel was flowing back to the tank. If that is not it, next best bet is to check the pump pushrod for excessive wear, lots of soft ones got out several years ago, I have a couple in the toolbox that were obviously dished.