Fuel Pump Upgrade

[Alpha D]

Question so what happens to fuel pressure regulators that rise at the 1:1 rate. Do they rise and then drop back to the set pressure once you go into vacuum? Or is fuel bled of through the return line to maintain the set pressure?

[mlomker]

Originally Posted by Alpha D

Question so what happens to fuel pressure regulators that rise at the 1:1 rate. Do they rise and then drop back to the set pressure once you go into vacuum? Or is fuel bled of through the return line to maintain the set pressure?

You normally set the regulator without the vacuum line attached. As an example, my car idles at 44psi or so but it'll drop to 40 under vacuum.