[robnitro]

Edit: Fixed, it was the rail pressure sensor. Swapped in a used one from europe and it's fine now.

I have been getting issues of rail pressure being erratic, causing stumbling and code 48A9 and 4560, sometimes one, or both.

First attack, cheap and simple, changed fuel filter and filled the tank up to be sure theres fresh fuel in case bad batch. Nope 2 tanks later, still issues.

First problem to eliminate, Low pressure fuel is stable all the time at 3.9 bar... no issues with the feed to the pump and through the filter.


Checked injector balance to see if maybe an injector is going bad, but am not sure since its "within limits of +-5.0"
So I noticed I have injector 3 as +1.0 idle and up to +2.0 in D.
the rest are within + or - 0.50 .
(This injector used to be around 0.5 but in winter jumped to that +1.0 to +2.0 range and has been steady since. so its not like it got worse)

---Would that mean that the injector might have leakback issues? Is that usually the case with a mechanically failing piezo injector? (I only know the electrically failed ones of 5 and 6 before, which can clearly be tested as a short to ground issue)

---Can I do the leakback testing without removing the intake manifold? (I don't feel comfortable running the engine with the intake manifold off)
If so, any reccomended kit - and any document that tells me what to do with the return line which will be pressurized?

If it is leakback it might explain why it only happens when warm out
During cold fuel and cold engine, the cp3 pump delivers at maximum rate (not pressure which we can see is 300bar at idle etc). This is governed by the pressure control valve (back of the rail- rail pressure regulator).

When fuel is warm- like now warm out... the pump goes into volumetric fuel control, meaning it pushes a reduced amount of fuel which uses the valve at the pump. (HPFP flow control valve).

This is the period where the rail pressure occasionally will start to fluctuate wildly and cause stumbling etc.

If I unplug the front rail pressure sensor, there are no issues but of course that is sort of a limp mode setup default map for pressure and flow.
It probably disables the volumetric mode too- making it full flow, so the leakback - if there is some, wont kill the rail pressure.

So I have a few choices on what to do.
-Replace the injector 3 since it has a sort of high number in balance. ($300 new) leakback - how common is this issue and is it usually signified by a high imbalance???

-Or could it be the HPFP flow valve on the pump ($70 new)

-or the relief sensor at the back side of the rail by the firewall ($40 used)
(but this doesnt seem to be right unless I am misinterpreting how it works, it regulates the rail pressure... which works fine when the fuel is cold and pump is in full flow mode)
<i>"The purpose of the pressure control
valve is to control the pressure in the
rail while starting the engine and when
the coolant temperature is below 19ºC."</i>



-or the rail pressure sensor ($200+- which I doubt because it doesnt cause issues - steady readings when the fuel is cold and in full flow pump mode)

[e90Noobie]

https://www.tunemyeuro.com/low-rail-...ry-controlled/

[robnitro]

Originally Posted by e90Noobie

https://www.tunemyeuro.com/low-rail-...ry-controlled/

Thanks, yeah I referenced that and other ones.
I'm going to try the leakback test as soon as I can find the containers

[robnitro]

Warmed up engine to 80 C fuel was at 36C
Leakback test for 15 minutes done. Some revving at 1500, mostly at idle.

The first 8 minutes was fine with the rail pressure sensor plugged in. After that it would start acting up and stumble and sometimes stall, so I did the rest with the sensor unplugged which runs fine but at a bit higher pressure failsafe.

None of the injectors were much more than the others. 4 5 6 are new 1 2 3 are original, with 3 being the one with +2 balance. 2 was a bit higher leakback than 1 and 3.

Total filled approx 70 ml, over those 15 minutes, which I think the standard is 2 minutes for 40ml, so not an overall excess leak.
_____________________________________

I don't think it's the rear relief sensor on the rail, because wouldn't that make it not run even with the rail pressure sensor unplugged?

Edit: I think that can be an issue because if it's worn, it can be slow to adjust pressure when hot. Found one on eBay for 40 used and will see if that changes anything. New is expensive!

The flow control valve on the pump, no clue how to diagnose.

And the rail sensor, it could be going bad but not sure why only when warm and in the volumetric mode... but fine in full flow mode. I don't think it's the same as the other 2 which have to work on actuation.

[robnitro]

Last week I tried a used fuel rail pressure regulator (the one at the rear firewall area) and no change.

I found a used rail pressure sensor for 70 and it should be coming next week.
If it's not that, I will get the hpfp fuel flow regulator from tunemyeuro and that should be the last variable eliminated.

I'm just amazed at how it runs without the rail pressure sensor plugged in. The default maps work pretty well. Mpg is a bit off because the ecu is guessing how much is being injected per stroke.

[welly]

I'm chasing a similar issue, albeit slightly different, and know how frustrating this is!

Any graph output of the rail pressure when it's having a wobble? Also you can log the volume control valve and rail pressure regulator to see duty cycle which may give some clues as the the profile of the problem. I'd say the flow control valve is the more likely of the two you're looking to try.

Lastly, you say supply pressure is at 3.9 bar solid, did you tee and measure with a gauge?

[robnitro]

Originally Posted by welly

I'm chasing a similar issue, albeit slightly different, and know how frustrating this is!

Any graph output of the rail pressure when it's having a wobble? Also you can log the volume control valve and rail pressure regulator to see duty cycle which may give some clues as the the profile of the problem. I'd say the flow control valve is the more likely of the two you're looking to try.

Lastly, you say supply pressure is at 3.9 bar solid, did you tee and measure with a gauge?

What conditions set off your issues? Is it an idle issue for you?

I didn't graph it but watched rail pressure starts spiking up and down randomly at idle, until it stalls..too little time to get much data. This didn't happen when it was cooler out.

Fuel supply pressure has been very stable and solid at 3.9bar, even before the fuel filter change. I use the stock filter with a 2 micron microglass fuel filter beyond it (former nicktane filter setup from my vw tdi), so I doubt it's from any dirt or water.

Tuesday I will be getting a rail pressure sensor from eBay, from an x5 35d with 100k on it
If this doesn't solve it, tunemyeuro has the regulator on the pump, for 75.

Hopefully it's the rail pressure sensor, because the regulator looks like a pain to change even with the intake manifold off, as there is a hard coolant pipe that restricts access to behind the pump on the x5.

[welly]

Only a WOT issue for me, I can see you had a look through my thread as well and had some useful input so thanks.

Such an odd problem this one, especially being temp related - Interested to see the results, fingers crossed for you.

[Yozh]

Definitely should log requested and actual on both PCV and FCV. FCV is a likely culprit cos you are getting 4560 which is delivery controlled. And FCV is used for rail control most of the time except below 19C motor and on coast down. Doesn’t mean though that PCV is closed. I would be logging the full LPFP side. And depending on if your car is stock 3.9 bar constant does not sound right. If it’s tuned depends on tuner then.

[robnitro]

Originally Posted by Yozh

Definitely should log requested and actual on both PCV and FCV. FCV is a likely culprit cos you are getting 4560 which is delivery controlled. And FCV is used for rail control most of the time except below 19C motor and on coast down. Doesn’t mean though that PCV is closed. I would be logging the full LPFP side. And depending on if your car is stock 3.9 bar constant does not sound right. If it’s tuned depends on tuner then.

On the x5, they have a different style pump in tank than the 3 series.
It's constant pressure, regulated by the pressure and temperature sensor which is up front right where the hpfp gets it's feed.

I forget if it's 3.9 or 4.9, but I know it's stable and barely changes (see below on how x5 pump works differently), just forgot the exact number and might have said it wrong above.
I'll see Monday or Tuesday if the rail sensor fixes it or not.


Low Pressure Fuel System - E90
The low pressure fuel systems differ between the E70 and E90. The E90 is a “speed regulated” system which means that the fuel pump speed is regulated by the EKP module based on request from the DDE.
The fuel pump will be activated with the “ignition on” signal. If the engine is not started, the fuel pump will be switched off after a defined time period. When the engine is switched off, the fuel pump is switched off as well.

Low Pressure Fuel System - E70
The low pressure fuel system on the E70 is a “pressure regulated” system which uses the signal from the fuel pressure sensor located in the low pressure fuel line.
The fuel pump operates with "ignition ON". If the engine is not started, the fuel is switched off at a specific pressure. When the engine is running, the fuel pump is regulated on-demand by the EKP module in response to a load signal from the DDE in order to ensure a uniform fuel pressure at the inlet to the high-pressure pump.
The functions of the low pressure fuel system are integrated into the DDE control module. The DDE uses the pressure information from the combined fuel pressure-temperature sensor to determine the current actual pressure in the low pressure system.
In order to maintain the approximate delivery pressure of 4.8 to 5.0 bar, the DDE uses a number of input variables. The input variables relevant to determining the adjusting value are:
• Actual pressure in the pre-supply system
• Engine speed
• Injection volume
The adjusting value is sent from the DDE to the EKP module in the form of a CAN message.

[robnitro]

Fixed, it was the rail pressure sensor. Swapped in a used one from europe and it's fine now.

[welly]

Originally Posted by robnitro

Fixed, it was the rail pressure sensor. Swapped in a used one from europe and it's fine now.

Good result. :-)

[robnitro]

Originally Posted by welly

Good result. :-)

I got 2 sensors in the mail at the same time. One from usa and one from Europe.
The usa one was newer and worked for a few minutes but then threw a code and stopped reading.
I was like fk! Maybe it's my ecu, I thought.

Swapped in the euro one from an e60 with same Bosch number, older revision and it's been good for a day+.

I really hate how sensitive these new electronics are.
Hopefully you nail your issue soon. Ps, my low pressure is 3.9 bar steady at any rpm and load. Not sure why the pdf said 4.9, unless they mean absolute, which is +1bar.
So if you figure almost 4 bar is 60 psi.

Part numbers here if anyone needs it

BMW GENUINE 13537787167 DIESEL FUEL PRESSURE SENSOR

This is the one on the back, aka the pressure control valve
0281002738

And the flow control valve is here, but it wasn't my issue
https://www.tunemyeuro.com/new-bosch...and-r70-pumps/
13517805529

[Looking4sushi]

I’m having some weird thing like this aswell.

Car : 330xd 2008 M57.

Bought car stage 1, clutch & flywheel where moshh.

Installed both new.
Went to tuner for stage 2.
Result stage 1 was already 278hp & 610nm
He did downpipe, egr delete ( swirflaps were already done ) and custom tune there while i was with him. Took almost a full day.

After tuning result 315hp and 730nm.
Me happy, finally going home, during rush hour so couldn’t go over 90kp/h.
I come home after 3 hours of traffic driving and decide to test the car the day after.

First ride, i ask a bit of power ; check engine light and car would stall.
Contact the tuner; he says its the valve @ end of comon rail.

I change it ( 200€ +- ) same problem, no change.
Next up, im like jo hey did you over tune my car or smth? To much rail pressure?
He keeps saying it’s not tune related.

Then he says lets test injectors.
Ok, 5 injectors come back completely out of whack. SUDDENLY while before the car drove really great!

I try to get him to meet me half way, he resists and says to change my injectors for 342€/piece without tva/btw.

I got them myself brand new 6 pieces for 1400€ since i work @ an auto parts store.

I do all by textbook, have a prof software to program the injectors.

Boem, all rides, same friggin problem.

Starts, idles, sounds perfect and drives, but as soon as you ask fuel, from 3000 he gets error again.

The car doesn’t run with fuel rail sensor unplugged , like i see with most it doest.
What is the culprit here still?
It’s costing so much with this guy, and it’s stil not solved.

My apologies for this rant, but spending already 4000€ for something that isn’t driving how it should, i’m loosing my shit and my wife not happy either!

[Andreive]

Originally Posted by Looking4sushi

I’m having some weird thing like this aswell.

Car : 330xd 2008 M57.

Bought car stage 1, clutch & flywheel where moshh.

Installed both new.
Went to tuner for stage 2.
Result stage 1 was already 278hp & 610nm
He did downpipe, egr delete ( swirflaps were already done ) and custom tune there while i was with him. Took almost a full day.

After tuning result 315hp and 730nm.
Me happy, finally going home, during rush hour so couldn’t go over 90kp/h.
I come home after 3 hours of traffic driving and decide to test the car the day after.

First ride, i ask a bit of power ; check engine light and car would stall.
Contact the tuner; he says its the valve @ end of comon rail.

I change it ( 200€ +- ) same problem, no change.
Next up, im like jo hey did you over tune my car or smth? To much rail pressure?
He keeps saying it’s not tune related.

Then he says lets test injectors.
Ok, 5 injectors come back completely out of whack. SUDDENLY while before the car drove really great!

I try to get him to meet me half way, he resists and says to change my injectors for 342€/piece without tva/btw.

I got them myself brand new 6 pieces for 1400€ since i work @ an auto parts store.

I do all by textbook, have a prof software to program the injectors.

Boem, all rides, same friggin problem.

Starts, idles, sounds perfect and drives, but as soon as you ask fuel, from 3000 he gets error again.

The car doesn’t run with fuel rail sensor unplugged , like i see with most it doest.
What is the culprit here still?
It’s costing so much with this guy, and it’s stil not solved.

My apologies for this rant, but spending already 4000€ for something that isn’t driving how it should, i’m loosing my shit and my wife not happy either!

Did you manage to fix it?
I have the exact same problem…