[mattlal]

Hey guys,

I’m trying to diagnose a low LPFP pressure issue on my 2007 E92 335i (N54) with a Walbro 450 LPFP upgrade (no port injection) and I’m running into a wall.

Symptoms:

LPFP pressure sits around 40–55 psi
Under load it won’t reach the expected ~70+ psi
Car is down on power / boost compared to normal

What I’ve already checked / done:

Found that the venturi (jet pump) hose inside the tank was not properly connected
Fixed that → pressure improved from ~30–40 psi to ~50–55 psi
But still not reaching normal levels
Checked voltage at the pump (via EKPM):
Around ~9.8–10V during priming
Bypassed EKPM (direct battery power to pump):
Pump gets ~12V
BUT pressure is still only 50–55 psi
So this seems to rule out EKPM / wiring as the main issue
HPFP seems fine (can hit ~2200 psi under load)

Current understanding:

Since direct power doesn’t increase pressure, it seems like a mechanical / flow issue rather than electrical
I already corrected one internal issue (venturi hose), but something is still limiting pressure

Next step I’m considering:

Checking/replacing the in-tank fuel filter / regulator portion of the assembly
Re-opening the bucket to verify:
Pump → top hat hose is fully sealed
No internal leaks or loose connections

Questions:

Has anyone seen an LPFP cap at ~50–55 psi caused by something internal like this?
Could this be:
A restriction in the in-tank filter/regulator?
A small internal leak still present?
Or a bad/incorrect Walbro install?
Anything else I should check before pulling the tank assembly again?

Appreciate any input — trying to avoid chasing the wrong thing again.

I have the walbro 450 lpfp

Here are the links to the logs one is with venturi unclipped and the other is with the venturi hose properly installed: https://datazap.me/u/halitofax/proje...07ju06hal4riik

Thanks 👍

[Sgop335]

Rail pressure is recovering slowly too and boost is not that high. Yes looks like it is fuel flow limited from the lpfp. What about the fuel filter sock etc? How was it w stock pump?