[Mr.Fixit]

Many race style fuel tanks with foam and bladder have a screen on the pickup which can catch debris before it makes it to the filter. The regulator is just a spring loaded bypass, but it can malfunction. Gages can be wrong as well. Have you noticed any fuel delivery problems while driving? The regulator has a bypass, and depending on design, if the bypass line cannot dump it's pressure, that can cause the regulator to not open until input pressure exceeds the static pressure in the bypass line (depending on design) thus no outlet pressure to carb. Just theorizing Check your lines for: kinks, sharp bends, and collapsing on the inlet to pump line. Also check filter cleanliness. If you can, verify the gage's reading with another. Check pressure before and after the regulator at the same time to verify the regulator is getting pressure. You can also disconnect the fuel line from the outlet of the pump and have it pump gas into a 5 gallon gas can, see if it starts losing flow as indicated by the gage far upstream. The electric motor could be getting hot and losing efficiancy.