I'm sorry, I don't know where the regulator is located, car is at the shop. Would the leak from the regulator be an external, visable leak? We're not detecting a leak of any kind or with dye.. I assume it has a fuel regulator, correct? I ask that because i thought i heard my mechanic say he was thinking about adding a fuel regulator, but he may have said he was thinking about adding a fuel pressure guage in the line because he's had gauges on it so often. Was thinking about trying to temporarily block off the return line to the tank. Idea being if fuel did not flow back to the tank it may indicate the problem was in the return line. Been chasing this problem for awhile, been to several LS/Corvette shops in Orlando. Was smelling gas toward the rear while cranking, changed the charcoal canister and smell is gone, but still loses pressure after sitting around awhile.
If we pinch off the fuel return line and the problem stops, the next question would be what's wrong with the return line? Is there a valve in the return line which is supposed to close so the fuel won't return to the tank? I believe the return line is just one line most of the way back to the tank(s), there are two plastic tanks, but then the line branches out into 6 lines. If pinching off return line doesn't stop the backflow, is there a valve on the line back to the pump?
Regarding the regulator in the fuel rail I now recall that, and remember someone saying the 'diaphram' can go bad. That has been changed if not the entire regulator. Been chasing this a year.
Regulator checks ok. Check valve from the feed line was my first thought too, but we have changed the fuel pump twice. Does the fuel return line also have a check valve so fuel can't drain back via return line?
You may be onto something big... I thought the check valve was part of the fuel pump assembly. You referred to it above as in the 'fuel feed line', as if it was separate from the pump, and more of an inline check valve. If that is the case, we probably haven't changed it. If it isn't part of the fuel pump how do we locate it, and does the return line have a valve too? Seems to be draining back to fuel tank in one direction or the other, and there is only so much it could be, feel like about to hit it.