It worked for a couple of days now no start. This is a log of it not starting. It’s on stage 2+, fbo. I also have a log from the day I installed the lpfp if you want to see it.
Datalog Replaced lpfp worked for 3 days now wont start.
- Thread starter ididsomething
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If you turn your RPM and Boost off in the graph and then turn on your Low pressure fuel sensor and your Rail pressure they are essentially the same .. doesn't look like your HPFP is working - it should be far above the LP reading.... maybe at a minimum of about 1500-2500?
Are you getting any codes and have you double checked the connections to your HPFP? I dont think your injectors have enough pressure to fuel the cylinders.
Are you getting any codes and have you double checked the connections to your HPFP? I dont think your injectors have enough pressure to fuel the cylinders.
Have you tried resetting your fuel adaptations . You first graft the rail pressure is not good. Looks like fuel is getting to the sensor tho. Check your grounds and connections on the hpfp etc. Theres a connector for the pressure solenoid on the HPFP .. Check your fuses also .. not sure if theres a fused circuit for the HPFP.
I only reset the fuel high pressure system on mhd. Should I reset other adaptations or use a different program?
What do you think about the second graph just after replacing the lpfp?
What do you think about the second graph just after replacing the lpfp?
I don't think your issue is related to adaptations .... you don't have any high pressure fuel to the injectors. Checking th e fuses and connectors to all of the sensors would be the first place I would look. Might even do a search for how to test if sensor is reading/working correctly.
The HPFP itself is mechanically driven, so a bit odd if it doesn't create some pressure. In the second posted log it shows it was building decent pressures, but something happened afterwards ....
What was the reasoning for replacing the Low pressure pump??
The HPFP itself is mechanically driven, so a bit odd if it doesn't create some pressure. In the second posted log it shows it was building decent pressures, but something happened afterwards ....
What was the reasoning for replacing the Low pressure pump??
Yeah it didn’t want to idle or run one day after work. Here is the log after the first no start. The lpfp dips pretty low so seemed like a logical fix. Throughout the year it would have mixture control codes. No other codes.
I checked fuses, connections and reset adaptations. I was able to get it to idle by giving it throttle and log it before it died. It gave me the yellow half engine light. This is the first code I got since the first no start. They were both high-pressure fuel pump.
Are there other things I can do to check if it is my hpfp?
Are there other things I can do to check if it is my hpfp?
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As z4dude pointed out, you have no rail pressure in most of these logs. In this one, your stft's are zero, and your lambda's are super lean. I would not push your car in this condition, I think something is going on with your hpfp.
Codes: 29f2, 2d33 shadow codes: 2aaf, 2fca, 2fda, 2fdb
Only thing I’ve changed in over a year is coils and plugs and that was in February 2025.
Only thing I’ve changed in over a year is coils and plugs and that was in February 2025.
hpfp are expensive theses days are there any other test i can do to identify the hpfp as the problem with it parked. I would rather pull it out and inspect it, then blindly order another one.
I get it... I'm in need of ordering one myself.
Not sure of specific test for HPFP... I'm following symptoms and codes myself that are pointing towards fuel pump.
In your case, you are losing your entire fuel pressure on the high side.
Not sure of specific test for HPFP... I'm following symptoms and codes myself that are pointing towards fuel pump.
In your case, you are losing your entire fuel pressure on the high side.
Your logs are definately pointing to an issue with your high pressure fuel pressure, whether it's the pump itself, it's wiring, or a fuse I can't say. But I can say that n54 hpfp's are notorious for failing. Even some of the off-brand units have been known to be failing right out of the box. You can certainly try to rule out wiring problems or blown fuses begore spending on a new hpfp. I'm n55 and have the new style hpfp, but of all the n54 threads I've seen, there are countless cases of hpfp's going bad. I don't recall any where it was wiring or a fuse, but that obviously doesn't mean wiring or a fuse aren't your problem.
How old is your hpfp?
Checked the fuses today they are good. It’s a 2008. I’ve had it for almost 30,000 miles. I haven’t changed it. I am not sure how old it is.
Technically, the N54 is designed to be able to run on the lpfp alone. Obviously it will have a check engine light and run in limp mode but, it should idle and drive. Im not sure if this is entirely accurate and a tune may effect this. But completely agree your hpfp is not working. Not sure on original source but the link is below and a copy of the statement.
"The injectors have a maximum of 40 mg/ms spray at 200 bar. This is an increadible amount of fuel, much much more than any solenoid injector. It is this high, because when we designed the application, BMW insisted that the engine must be able - in limp mode - to only use the LPFP pressure, which is 5 bar, and still drive the vehicle at 170 km/h."
www.spoolstreet.com
"The injectors have a maximum of 40 mg/ms spray at 200 bar. This is an increadible amount of fuel, much much more than any solenoid injector. It is this high, because when we designed the application, BMW insisted that the engine must be able - in limp mode - to only use the LPFP pressure, which is 5 bar, and still drive the vehicle at 170 km/h."
N54 Piezo Fuel Injector Limits
Injection window is the big limiter to the stock di setup. At some point, that window closes and the only way to inject more fuel without fully wetting the cylinder walls comes by way of pi. Can you explain that further? I'm not sure I understand what that actually means. Filippo
www.spoolstreet.com
OK again check the wiring harness - If you look on the diagram there's an electric connector circled #15 .. That controls the solenoid inside the HPFP. If somehow you disconnected that or that wiring harness is damaged the HPFP wont work. Your rail pressure in one of your logs was ok and now it's flat. Maybe you mentioned you checked that, but it's not a fuse it's on the HPFP itself near the LPFP sensor connector.
HPFP. Pressure - Bimmerprofs.com | NOx emulator NOXEM 129 | 130 | 402 developed for BMW N43 & N53 series engines
In this entry, I will explain the concept of HPFP pressure maintenance. The HPFP pressure is maintained with a closed-loop system. To measure the pressure, the pressure sensor, located in rail, is used. In the picture: Rail pressure sensor is marked. To regulate the pressure, an...
bimmerprofs.com
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