Low FPR with external setup

pysical

Sergeant
Jun 16, 2017
471
108
0
Ride
2009 335xi E90
I changed my setup to an external FPR setup. I basically have one 450 (PI pump) that bypasses everything and comes out of the driver top hat. The main 450 uses the both venturis.

When I first set everything up I set the FPR to 72 psi and it was fine for a couple days. Then It out of no where started to dip to 40s and 50's while idle and normal driving.

Is this expected? I have been trying to find a leak but can't find anything.
 

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pysical

Sergeant
Jun 16, 2017
471
108
0
Ride
2009 335xi E90
I tested pinching off the return line and pressure didn't change. I pinched PI line and pressure didn't change. I pinched the pi pump line that meets the other line and no change. So i feel like it is somewhere from main pump to driver top hat in the tank maybe. I checked my screw to block old fpr and its still in. I tested the main pump prime with protocols and it only went to 55 psi. Not sure if it should be higher or if it only targets that.
 

Jeffman

Major
Jan 7, 2017
1,628
1
631
0
I changed my setup to an external FPR setup. I basically have one 450 (PI pump) that bypasses everything and comes out of the driver top hat. The main 450 uses the both venturis.

When I first set everything up I set the FPR to 72 psi and it was fine for a couple days. Then It out of no where started to dip to 40s and 50's while idle and normal driving.

Is this expected? I have been trying to find a leak but can't find anything.
Mine does the same thing. Did you ever resolve it?