Just figured out how to attach my FP gauge to the fass. Needed a special fitting and some fuel line. My question is: right now I have a FP of 15.5 (constant) but as this was hooked up, air was essentially in the line instead of fuel. This is hooked to a mechanical isolator which then goes to the cab. Will I get more accurate FP readings with fuel in the line or at such low pressures will it not matter if its air or diesel?

 

with my fass system, i have 21 psi at idol, i am hooked up to the Vp44 schrader valve and i do not use an isolator, i have a mechanical gauge and run fuel straight to it

 

Air in the line will not change the pressure, just absorb the vibrations.