My fuel pressure keeps jumping on my gauge. I'm running a brawler 750 carb and it's supposed to be run at 6.5 psi. However, when I go to set it at 6.5 psi the gauge jumps rapidly between like 5 and 12 psi. If I set the pressure below 6.5 psi, say like 6 or 5.5 psi, it stays steady and doesn't jump. You can hear the fuel making a thud noise kinda like when you shut off a main water line in your house, you hear a thud from the water pressure. That is what this mallory regulator is doing. The in tank pump is a TPI pump and it's basically brand new, only about 500 miles on it. Does anyone know what could be wrong here? Maybe a bad pressure gauge?

 

Do you have the return line hooked up?