Hey I have a Mallory FPR w/return using the intake EFI 255gph fuel pump. Even when I remove the adjustment screw completely, the fuel pressure remains at least at 8lbs. I've read thorugh some old posts and there have been some similar problems but most were left unresolved on the message boards. I was thinking of installing a 2 port carb FPR between the mallory and the carb to tune it down to 5lbs. Any ideas or suggestions would be appreciated. I am using 3/8 inch fuel line for the return to connect the mallory regulator back to the stock fuel return line.

 

Thats generaly an indication of a restriction in the return line, possibly just that it's not big enough. I suggest you run the shortest, fatest hose you can just into a gas can, see if the pressure goes down.

 

You have the right springs & washers combo in the regulator for low pressure applications right?If so and if the pressure doesn't go to 0psi when you remove the adjustment screw it means your return line is too small as per the Mallory instructions (read them..alot of good info)..too restrictive.I run a -6AN feed with an -8AN return line on my fuel system with a Holley pro series black pump.0psi with screw removed...6psi set at carb when car is running.

 

thanks for the replys, i already read the instructions and i figured that my return was too small like you guys suggested. I took a Carb FPR i had laying around today, set the pressure to 5lbs, and stuck it between the mallory and the carb to see what would happen. It seems like the second regulator is forcing the excess pressure back through the return line and now my guage reads a steady 5lbs. Do you guys see a problem with this set up. Also if i were to install a larger return line, how hard is it to properly route it back to the fuel tank.

 

Thats not good. It will run fine, but without a sufficient return line you're putting extra strain on the pump, which will shorten it's life substantially.

 

In my understanding the Fuel injector fuel pump is designed to be used with high pressures 40+ lbs that fuel injection needs, whereas a carb pump is not, with this setup, my mallory sets the pressure to 12lbs and the other regulator then reduces it to 5. If im thinking of this correctly, then the pump is only under a constant 12lbs of pressure which is way lower than it was intended to run.