[badassf4i]

since I bought my 2007 335i it has always shown around 40 psi on the jb4 gauges. the car runs ok in spite of that. well I just did the stage two pump upgrade and it is still showing the same thing.the car still seams to run fine with no codes but this just dosent seem right. I tried adding a little e85 last night with a back end flash and it wants to miss under boost. never had this problem with 93 so im wondering if the low pressure is playing a factor.

[pits200]

Could be the sensor giving a bad reading.

[nukezero]

fuel pressure regulator

i just replaced mine. the fuel pump is not the one supplying fuel to the hpfp. It's job to pressurize the line. But the actual "sending" of the fuel , it's actually the job of the regulator (a.k.a. german term: fuel sending unit).

hence the word fuel "pressure" "regulator"

The regulator's job is to ensure the low pressure fuel line is always around 70psi before engine start and after engine shut off. This is why replacing the fuel pump won't do jack because the regulator is broke or on it's way out. You can pump a thousand PSI into a faucet line, but if the regulator(check value) just before the faucet spout is leaking, then your faucet spout is obviously not going to get thousand PSI output.

See my technical post here:
http://www.e90post.com/forums/showth...ght=long+crank

[muncie21]

Post a log. If the lap fuel is a virtualy a flat line it's likely the pressure sensor under the intake. If your pressure bleeds off after sitting, likely a regulator issue

[jwebb335xi]

Originally Posted by muncie21

Post a log. If the lap fuel is a virtualy a flat line it's likely the pressure sensor under the intake. If your pressure bleeds off after sitting, likely a regulator issue

Key on , then log....? Then start and log? Then drive and log?

[muncie21]

Yep, that's the sequence. You don't really need to drive it. You see the pressure rise when you start it.

Here's mine before sensor replacement


And here's after