Limp mode - is it the high pressure fuel pump??

T

Tornado

Member
HI ALL E89 lovers,
My faithful Tornado, e89 2000 35i, coughed and spluttered on startup Sunday afternoon, then the half-engine light came on. I stopped the car. Flipped the bonnet, just to check. (not that there's much I can check - not even a dip stick!) But I could see no leaks or disconnected wires.

I started the car again, and it seemed to work fine. I scanned it a couple of times with my C-Reader (which always feels dodgy) and came up with some alarming codes that then disappeared:
  • 2F9E DME: Oil level
  • 29F2 DME Fuel High-Pressure System

I did the electronic oil level check (hate that thing - give me a dipstick any day) and it said oil level was normal (halfway between min and max)

When the engine light comes on (sometimes the car drives completely normally) it goes into "Reduced power" mode and says I can "still drive conservatively", but it won't even reverse uphill. Major loss of power.

These codes above disappeared. I don't understand why, because the trivial codes about interior lights being the wrong load ALWAYS show up every scan.

So, am I going to have to go through the financial pain of getting a new high-pressure fuel pump installed?

I'm not even sure if I will be blessed to get it to the garage.

(The car has just passed 200'00kms)
 
You need to data log the HPFP rail pressure ..anything below 1500 psi under load is the definitive diagnostic
 
I graphed the Fuel Rail Pressure on my C-Reader scan tool.
see image
It seems to sit at 300KPa during idle. ( I think this is the low-pressure side through)
 

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Tornado said:
I graphed the Fuel Rail Pressure on my C-Reader scan tool.
see image
It seems to sit at 300KPa during idle. ( I think this is the low-pressure side through)
Click to expand...
On E89s there's no low pressure fuel rail monitoring, looks like thats the HPFP rail at idle..it needs a WOT pull from 1,500-6,500 whilst being data logged..it normally collapses somewhere after 2-3k
 
Thanks. That’s interesting to know. That would explain why I only get one reading on my C reader elite 2.

Well, one of the pumps is not working. If it’s sitting at 300kpa that’s about 3 bar. The low pressure pump is supposed to be 5 or 6 bar (according to Chat GPT 😝). So it is probably the low pressure pump failing and starving the high pressure pump.
 
You need a code reader first and foremost…bmw specfic..without it your pissing in the breeze…
 
Yes I have a BMW-specific version of the C-reader Elite 2, although I'm not that confident using it to be honest, as I don't have much experience with engine computers.

Anyway, when the problem went from occasional to a little more frequent, I took it to a mechanic specialising in BMWs.

They have
  1. replaced the Low-Pressure Fuel Pump,
  2. replaced the High-Pressure Fuel Pump,
  3. reset the adaptations,
  4. and reprogrammed the DME
I was thinking it was the control signal to the High Pressure Fuel Pump, but apparently the DME would sense if that wire was shorted to ground, 12V or if it had broken and gone open circuit, flagging a “Fuel pressure control, electrical” or “Fuel pressure, plausibility” code.

Maybe it's the sensor... Hopefully they checked that ...

They are now sending it to BMW.
 
So BMW replaced the HPFP again and said it is fixed. My guys hand the car back and charge me 6K.
I feel like there should have been better diagnosis than replace parts and hope it will be fixed soon.
They seem to have replaced
senso
LPFP $1200 WTF?
LPFP filer $700! WTF?
HPFP? $2000 What TF?
And $2000 labour which I wouldn't mind so much if they had fixed the car, but it's still broken - drinking oil and complaining about DCT overheating.
Now I read that not even BMW knows how to service their DCT, so they will probably replace the mechatronics pack for oh just around $6000 and that doesn't include clutches... like have I just been really unlucky or is this standard expenses for owning one of tehse cars? It is coming me about $10 per kilometre.
 
I could go on at length …

However very very unlikely that LPFP and HPFP fail..

Where do you live ..what fuel do you use?

Year of car and mileage?

Most DCT issues get fixed with fresh fluid and filters..correct fill procedure pls..
 
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