[georgenov]

Hello everyone!

I have an ongoing issue with my 2011 BMW 335i. It's N55, but as you may know, E90 has the same HPFP on N55 as N54.

My history with HPFP issues started 8 months ago when I got a long crank on the cold engine and a set of errors told about HPFP failure, then failure started happening just during driving. It was the time I decided to change HPFP since I was not able to afford a new one (currently $1,100+) I got the used one from the low mileage car.

Everything was fine after the change, I monitored how rail pressure was following the setpoint and was happy about how the pump worked until I got 2C01. Turned on the cold car, let it warm, then went outside the parking lot and immediately hit traffic with frequent go-and-stop motions. After a couple of such motions, during the lowering speed phase (releasing the acceleration pedal and pressing the brake) I noticed that rail pressure went down (about 150-200 psi instead of the expected 700+), the engine was struggling and almost immediately 2C01 appeared. I pulled over, restarted the car, the error became inactive.
Since I was happy with how HPFP performs in other conditions: stable pressure on idle, and fast pressure growth, I decided not to research this issue.

Next time the same pattern happened around 2 weeks later, and then I decided to look deeper.

I started noticing that this behavior with rail pressure PSI dropping to 200-300 happens during sudden brake, or when accelerating and then braking. It usually happens when the car is very close to stop.
Then I decided to check what ISTA says about HPFP, and run a test that checked how rail pressure has been handled on different levels on idle - it showed me that everything is good.

After that, I decided to see the setpoint vs actual rail pressure values.
Here's the video on youtube that I captured from ISTA. On this video, you clearly can see how the rail pressure value drops below the setpoint and it takes 10-15 sec to gain a setpoint value.

I'd like to hear the opinions of people here in which direction should I look. May it be that this HPFP is also faulty, but in that very specific flavor? May it be something else?

I'd like to highlight the fact that on idle rail pressure is stable and during acceleration, PSI grows instantly to the setpoint. The issue with rail pressure happens only when braking/releasing the accelerator.

Thank you all in advance.

[Xramses]

I bought a cheap HPFP from ebay, failure still ongoing. copy from my other reply in another thread:

Hey e90ies I am an e71 ,
My HPFP is also showing up fails 2C01 (hpfp) and combined with throttle and fuel gas mixture power loss (28A0 & 2BEA). First before winter Nov2023 irregularly and since one week continuous failure. Reduced motor power. 191t km.
for my x6 I bought a replacement HPFP from ebay, replaced also the high pressure sensor. still having the failure. Wondering if the ebay (labelled as new) is a incorrectly refurbished one.
I checked the electronic control for the HPFP-regulator solenoid. putting a 12volt build into the electric plug and then: opening door -> soft power/light. starting motor -> more power/light.
So further I will check if the vacuum pump is working right and able to rotate/drive the HPFP, by rotating the crankshaft.
I will definitely try also with the original HPFP which is now out to refill and to replace the rubber seals (3 o-rings and 1 main HPFP-axis) like this good video (the solenoid of the original HPFP is still working):

[Xramses]

My issue with the HPFP is gone for now. I followed the oil refill instruction. But just without bath. Filing of three pistons and main body. Also the pump front rotating the T-crank to get rid of air. Then flipped the main body into the front. A third hand filled some oil with a spoon when closing and pressing together. The third hand of my daughter fixed the three screws. I took hydraulic oil. then good washing with brake cleaner along the fuel in, out and solenoid openings. Then attached the solenoid. Bingo!