Hi guys , need some help in diagnosing a fuel pressure problem.
Its is not an efi car. Here gos smallblock chev 355, BG750, areomotive pump (efi) with return port, 1/2" fuel line,-8 return. If the car is off and pump running there is no pressure loss (8psi) and stable. when the car is running and warm the pressure drops to ( 2psi). Tried new regulator, new pump, new filter, there also proper voltage at the pump. This is not my car but a freinds,no one including areomotive tech can solve. Any ideas would be appreciated greatly, the only thing i can think of is to big a return line,and bleeding pressure if Im wrong please let me know
thanks in advanced! ive also posted in general section with no luck/reply

 

The regulator should be controlling the pressure based on the pressure to the outlet, not the return (certainly not the return line size).

Either the pump isn't keeping up its part of the bargin, or the reg isn't. That, or something isn't hooked up correctly.