This is from a post on
http://forums.bimmerforums.com/forum/showthread.php?604356-318is-N-A-M44-fuel-pressure-psiEngine off, with the fuel pump ran for approximately 1 minute, the pressure should be.
3.0 BAR +/- 0.2 BAR
43.5 PSI +/- 2.9 PSI
After 20 minutes, the residual fuel pressure should not have dropped more than 0.5 BAR
Then, once the engine is started and idling, the fuel pressure should drop 0.4 - 0.7 BAR compared the values above (3.0 BAR / 43.5 PSI). Due to the vacuum on the pressure regulator.
If you remove the regulator vacuum hose, when idling, the pressure should "increase". They don't list any values.
Again, I don't know if that helps you, but maybe it'll help someone someday.