MFI Fuel Pump and MFI pump Design Intent

[47silver]

How does an mfi fuel pump and MFI pump delivery work?
I am thinking that the pump is always circulating gas from the tank supply to the tank return.
The MFI pump then draws away the fuel that it needs and the resultant pressure drop increases the amount of fuel the the fuel pump delivers which keeps the amount circulating back to the tank at a constant.

if not then what it the purpase of 3 lines connected to the MFI fuel pump?

[356RS]

You are correct. The electric fuel pump will keep a positive pressure to the MFI pump fuel head even at WOT and 7500 rpm, although that positive fuel pressure may fall down to a low .50 to .25 bar. Large 3.0 + street engines can see almost zero pressure at the MFI pump fuel head and still work fine. The RSR engines added a second electric fuel pump in parallel to keep the pressure up at WOT and 8000 rpm's.