[stn54]

Hey I’m having a interesting fuel pressure issue, it’s almost like the fuel lines have air in them or something. The car is normally on full e-85 but to figure out my issue I’ve put it back on 93 pump gas. It appears the low pressure fuel pressure is spiking it drops to 30-40psi, and crashes the hpfp but then spikes up over 100psi but it’s running a stage 3 lpfp bucketed unit. now I believe I’m correct but 1 of those walbro 450 fuel pumps can’t pump the 120+psi the car says it’s making when it spikes. I also have reflex pi controller with the aux pressure sensor in the port injection rail so I know the oem low pressure fuel sensor is good since they both do the same thing. I have a short log of trying to drive the car….


https://datazap.me/u/n54ian/map-1?lo...30-56-43-49-34

[whyzee125]

How are you controlling your pumps? 1 off the EKP and 1 off the Hobbs switch?

[stn54]

Yes I have the precision racewerks with that hobb switch harness, I also got a oem ekp from a parts 335i I have.

[whyzee125]

I'd be highly suspicious of your LPFP sensor. It's normal for the pressures to jump around but your spikes don't reach nearly 120 on your aux sensor. Those pressures seem feasible to me.

As far as them dropping so low, you may have an EKP issue as well. 450's will cause issues if your EKP isn't nearly new. But IMO start with your LPFP sensor as I don't think the 450 is capable of the pressures the car is showing.

[stn54]

Ok luckily I ordered a new sensors and a fuel pressure regulator I’ll install my sensor and get back to you thank you..

[stn54]

Ok so installed my new low pressure fuel sensor and no change they still jump around and the 2 sensors are slightly apart from each other still

Update issue sorta fixed. So I replaced my fuel filters and fpr and that was the problem, I even bled the lines and my low pressure fuel pressure went up 13psi in general. the car doesn’t have that spiking issue now but my hpfp is bad and it’s still crashing but not because the low pressure anymore.