Total Volumetric Fuel Flow - 1999 Cat 3126 DITA MUI

Good afternoon,


I'm working on installing a Maretron fuel flow meter, and I need to know the total fuel being pulled by the fuel pump, not just the amount consumed by the engine.  Maretron's manual states that only about 20% of the fuel pulled through the lines is actually burned and 80% is returned.  Does anyone have any idea how much fuel would actually flow through the supply line flow sensor?