Was having issues with my car losing fuel pressure under boost. It would drop to 10 psi when I stepped on the gas. After some prelim testing, changed the sending unit and installed a Walbro 255lph high flow pump. Was still having the same problem. Wired and plumbed out my external helper. Problem solved. I now see over 65psi with high boost. New problem: When I turn on the key and let the system prime, the fuel pressure goes straight to 0. Had someone prime it and I pinched the feed line, pressure holds. Problem is in the tank as I pinched the feed line right under the tank. Car runs great. My question is: I have either a bad pump off the shelf or leaky check valve or pulsator. Any ideas or suggestions? If my car runs ok, do I need to worry about this? As we all know, dropping the tank bites, but if I need to, then I need to. Thanks.

 

Is your "external helper" an inline pump, or is it a second pump with its own sump?

When you say you "plumbed out" do you mean your removed it from the system?

Is your fuel pressure regulator boost referenced?

 

It's an inline helper from Procharger. I pulled the relay to it and my problem persisted, so I pulled the fuel line and bypassed the pump so it's out of the equation as thought it was never there. My pressure came back. My fuel pressure regulator is boost referenced. I had the tune set up on a dyno here locally and everything has been fine for about the last 5 years. Like I said, it seems to be running ok except for the pressure charge at prime. Pinching off the feed tells me it's in the tank. I'm just not sure if I need to worry about a bad check valve or a leaking pulsator or something or if I'm missing something else. If my new pump is bad, well.............
I've had the tank out before!!