Low fuel pressure help!!!

E90steph

New Member
Feb 21, 2021
4
0
0
As this states I'm running into a problem with my low fuel pressure. During pulls it stays at 55 and my high pressure fuel pump suffers Hoping I can get some answers here. I have 2 walbro 450s a new high pressure pump, bpm4, all new fuel sensors and fuel line I have also replace the fuel pressure regulator and still no luck. I have 0 idea where to go next my tuner thinks it could be a dme issue any insight would be helpful thanks in advance.
 

rev210

10 Sec Club(N54)
Feb 24, 2019
159
70
25
Ride
335i - 08 Coupe .
Do you have Port injection? Also the fuel pressure reg, is it set to static or rising rate? 55psi isn't horrible , I have twin 450s also with motive PI (Ai6 controller). Lastly , what fuel? Assuming E85? If you are sticking most of the top end fueling through the DI injectors and not PI, the HPFP runs out of huff at a point unless you get something like a POD from PFS , VTT shotgun or helix.
 

E90steph

New Member
Feb 21, 2021
4
0
0
Do you have Port injection? Also the fuel pressure reg, is it set to static or rising rate? 55psi isn't horrible , I have twin 450s also with motive PI (Ai6 controller). Lastly , what fuel? Assuming E85? If you are sticking most of the top end fueling through the DI injectors and not PI, the HPFP runs out of huff at a point unless you get something like a POD from PFS , VTT shotgun or helix.
I'm not running port yet because I'm wanting to fix fuel pressure first. I'm on e30 currently and same thing I won't raise my E till I fix this issue. Also im not sure what the regulator is set to I wasn't aware that where was a setting for it I thought it was just out with the old and in with the new.
 

NoGuru

Lieutenant
Jan 9, 2018
962
404
0
Just North of Detroit
Ride
BMW 335is
Is the duel 450's a DIY or Off the shelf purchase, who made it?
Are the 450's authentic, where were they purchased from.
Is one of the pumps on a Hobbs?
Is the wiring correct for the pumps or hobbs?
 

E90steph

New Member
Feb 21, 2021
4
0
0
Is the duel 450's a DIY or Off the shelf purchase, who made it?
Are the 450's authentic, where were they purchased from.
Is one of the pumps on a Hobbs?
Is the wiring correct for the pumps or hobbs?
It's precision race works where I got them. And one pump use to be on a hobbs now they are both on a bpm4
 

rev210

10 Sec Club(N54)
Feb 24, 2019
159
70
25
Ride
335i - 08 Coupe .
I'm not running port yet because I'm wanting to fix fuel pressure first. I'm on e30 currently and same thing I won't raise my E till I fix this issue. Also im not sure what the regulator is set to I wasn't aware that where was a setting for it I thought it was just out with the old and in with the new.
Guessing you have upgraded turbo/s ?
Also assuming you have not only the twin 450s from precision but also a proper bucket/bucket less mount from there too?
The standard hpfp and DI can only deliver a certain amount of fuel , it has its limits. Possibly , you are close to maxing it out, hence your low pressure looks ok but, your tanking on rail pressure. People can chime in here but, from memory 500whp or so on E blends would be about it and then the rail pressure drops.
 

STE92

Corporal
Mar 3, 2017
170
47
0
Ride
E92
Make sure both your pumps are connected, maybe one connection broke off on installation. Also had a fuel line burst inside the tank and my pressure would drop.
 

EOSpeed

Corporal
Nov 7, 2016
109
158
0
Chicago, IL
With the car running you can use the BPM4 software to manual override your pumps to 100% just be clear this should only be used to test your system. After doing a log make sure you reset the manual override command in software after test.
 
  • Like
Reactions: NoGuru