[klingon55]

2010 x5 with 160k
Deleted


Before: 4BDA 4BDC
Symptoms, cannot exceed stock rail pressure on tune. But WOT is able to reach commanded rail pressure within 70 bar. No limp mode issues until the VCG was replaced.


Popped my VCG


I replaced the VCG on my X5 and the LPFP with a known good.

2 injectors did not survive the VCG replacement, misfires at idle
Also new symptom, rail pressure will not exceed 1240bar and causes car to shut off in limp mode.

4BDC and 4BDA still present
Codes for rough running in cylinder 4 and 5
Codes for 0 quantity on 4 and 5
4560
4570

Replaced injectors 4 and 5, reset all adaptations

No more rough running, or misfires, but rail pressure issue still exists.

Replaced metering valve and reset adaptations no change
Replaced Pressure control valve reset adaptations no change
Replaced rail pressure sensor reset adaptations no change
Replaced r70 with a r90, reset adaptations with no change
Checked LPFP pressure, tests in ISTA at 4200mbar with fuel system test and the full test reports no problems
Lpfp pressure is 3200mbar at cruise
Fuel bypass quantity test done , all were within acceptable levels at idle

The fuel filter was changed 10k ago

Current codes are
4BDC
4BDA
4560
4570

When watching rail pressure, part throttle can reach commanded pressure up to 1447 bar
Wide open throttle rail pressure hits a brick wall at 1240 bar then limp mode and car cuts off if held for more than 3 seconds of wot

Oddly lamda does not lean out during the fuel pressure issue, it stays at the 1.1 to 1.0 target depending on conditions

Thoughts ?





The TLDR is that it got fixed after I replaced all injectors once more with tested units. But there may have also been an issue with the fuel rail because we swapped that at the same time that I did the last 2 injectors.

[klingon55]

Just an update, if the car has been sitting for a couple hours I can warm it up to operating temp, and get 3-4 full pulls in that hit 1450-1500 bar, after 4 pulls the car returns to only being able to get to 1100-1240bar under wot.

[robnitro]

Did this car ever use a tuning box or anything else to go very high in rail pressure?
With tuning boxes, they fool the sensor even past the point of 2000bar max sensed.
If you exceed 2000, the relief valve opens. If it opens a couple of times it doesn't seal well anymore. Known in the Cummins trucks that use the same pumps as ours.

[BB_cuda]

Originally Posted by robnitro

Did this car ever use a tuning box or anything else to go very high in rail pressure?
With tuning boxes, they fool the sensor even past the point of 2000bar max sensed.
If you exceed 2000, the relief valve opens. If it opens a couple of times it doesn't seal well anymore. Known in the Cummins trucks that use the same pumps as ours.

Rob, is relief valve downstream of HPFP but before injectors? Presume valve would dump into tank return line. Thanks

[ranthum]

It's my understanding that there is a calibration curve for the fuel rail pressure sensor. Maybe the rail pressure is fine and the signal being sent by the fuel pressure sensor (0-5v) is fine, but the computer interprets it incorrectly. IE fuel rail pressure sensor is sending 4 v which should be say 1500 bar but the dde associates 4 v with 1240 bar and thinks the rail pressure is low and goes into limp. The only reason that I would think this is if your afr lambda stays in check it appears that your rail pressure is fine. Or maybe there is a damaged wire for the fuel rail pressure sensor. You've replaced everything that I could think of that would cause an actual low fuel rail pressure and with an r90 you should have no trouble hitting 2000 bar.

[Owen81]

If it gets worse when the car is up to temp, perhaps the fuel temp sensor isn't reading correctly and its dumping fuel back to the tank?

The 335d seems to have it, #4 here:
http://www.realoem.com/bmw/enUS/show...diagId=13_1149

But I can't find it on the X5 diagrams.

[robnitro]

Originally Posted by BB_cuda

Rob, is relief valve downstream of HPFP but before injectors? Presume valve would dump into tank return line. Thanks

I think the valve is at the end of the rail.
It looks like this:

https://www.turbodieselregister.com/...-valve.174334/

"Dumb question, but I'm a newbie here. Is the pressure relief valve on the fuel rail, or before the CP3? I'm assuming it's on the rail somewhere.
yup its on the fuel rail. "

[klingon55]

Originally Posted by robnitro

I think the valve is at the end of the rail.
It looks like this:

https://www.turbodieselregister.com/...-valve.174334/

"Dumb question, but I'm a newbie here. Is the pressure relief valve on the fuel rail, or before the CP3? I'm assuming it's on the rail somewhere.
yup its on the fuel rail. "

The valve on the back of the rail has been replaced if this is the same as the control valve.

I dont know the prior owner of this car, however in my ownership it has never had a JBD or anything of the like.


I will check with my tuner for scaling but I am pretty sure its stock.

As far as the temp readings go, the fuel temp readings were correct when viewed on ista.

I cleared the codes 2 days ago, currently all I have now is 4610, 4560, 4570

[robnitro]

I don't think it's the same as the sensor/device on the back of the rail. That's the regulator. This is a fail safe that bleeds pressure when you exceed 2000bar, in case the electronics fail. It's a relief valve that doesn't normally operate ...

[klingon55]

Originally Posted by robnitro

I don't think it's the same as the sensor/device on the back of the rail. That's the regulator. This is a fail safe that bleeds pressure when you exceed 2000bar, in case the electronics fail. It's a relief valve that doesn't normally operate ...

Both front and back of the rail are electrical connections there is no relief valve that isn't electrically connected.


Adding one code to the list
New today -> 4600
4610
4560
4570

The pre-supply codes still have not come back. I am hoping that if its an injector it will eventually fail enough that theres a code for it, I'm really in a holding pattern because the car drives well enough for me to get to work and it has drained me of money. I do have a fuel filter on the way just for shits and giggles.

[robnitro]

http://www.realoem.com/bmw/enUS/show...diagId=13_1150
I would guess either the back end of the rail sensor having this relief as part of it, since the #4 is the return line that the extra would flow into.

The fuel temperature sensor on the x5 is part of the feed line along with fuel pressure lpfp.
http://www.realoem.com/bmw/enUS/show...diagId=13_1231 #10 is the line and the #14 plugs into that sensor

[klingon55]

Originally Posted by robnitro

http://www.realoem.com/bmw/enUS/show...diagId=13_1150
I would guess either the back end of the rail sensor having this relief as part of it, since the #4 is the return line that the extra would flow into.

The fuel temperature sensor on the x5 is part of the feed line along with fuel pressure lpfp.
http://www.realoem.com/bmw/enUS/show...diagId=13_1231 #10 is the line and the #14 plugs into that sensor

The pressure control valve on the back has already been replaced

I put a new fuel filter on today and there's no change in behavior so its got to be one of the 4 injectors I didn't replace.

[klingon55]

Got a working k+D-Can cable, tested low pressure fuel under load, its 3.9 to 4 bar under load and does not drop, so its safe to say that the feed pressure is fine, only thing left are the injectors.

[klingon55]

Update:

Purchased 4 injectors
3 used but I sent those to a certified Bosch Tester and they all passed.
1 brand new injector

Installed used on 1, 2 , 3, and the new one on 6 coded them.

Runs a lot smoother, but the same issue persists. I suspect that the 2 used injectors I installed on 4 and 5 may be the last cause of this, as they were never tested.

Right now Im going to wait a few weeks but if the car doesn't sell I will send the 4 i took out off to the Bosch testing place and see if I can get 2 good ones out of the deal and install on 4 and 5 and code them. But thats where I am at. I see a lot of this on the forums and all the threads just go quiet, so giving this level of detail should help others even if I no longer have the car, and I will ask whoever buys it to let us know what the fix was. Im about $2800 deep into fixing this fuel issue and Im throwing in the towel lol.

[robnitro]

Just to confirm, you replaced this relief valve? See second picture
https://www.oreillyauto.com/detail/b...bmw/335d?pos=0

[Yozh]

What about the fuel temp/pressure sensor on the feed line? It is an X5 and has a pressure sensor together with a temp sensor. I know you have replaced every component imaginable and your tuner tried every option possible to rule things out. The other thing to look at also is what contributes to the fuelling control are the MAF and O2 sensor. I trust you had run all of this through proper logging to see what is happening to rail pressure and which actual control aspect is affecting the rail pressure.

[klingon55]

Originally Posted by robnitro

Just to confirm, you replaced this relief valve? See second picture
https://www.oreillyauto.com/detail/b...bmw/335d?pos=0

Yes it was replaced with a new one.

Originally Posted by Yozh

What about the fuel temp/pressure sensor on the feed line? It is an X5 and has a pressure sensor together with a temp sensor. I know you have replaced every component imaginable and your tuner tried every option possible to rule things out. The other thing to look at also is what contributes to the fuelling control are the MAF and O2 sensor. I trust you had run all of this through proper logging to see what is happening to rail pressure and which actual control aspect is affecting the rail pressure.

It has not been replaced but it reads the correct commanded pre supply pressure. Under wot or part throttle its at 4 bar. The AFR is correct and matches commanded.

[klingon55]

Guys,

Last Friday I went back to BRR and we replaced injectors 4 and 5 as well as the entire fuel rail. This resolved the issue, then we coded all the new injectors. I had some random misses on the way back home any time i would roll off throttle. The next day I filled up and put a healthy dose of Hotshots in and it had one single more misfire that day. Fast forward to now, no misfires, no fuel issues, no boost issues, no codes. I hold 2.7 bar of boost and 1800bar of fuel.

[Bull3t Proof]

Sorry to Resurrect this....lol.

Have a N57 with L93 Fuel Pump - M50d Sensor (Scaled on map)

If i exceed 2300mbar of fuel rail pressure... WOT, car stalls everytime. Hot or Cold...

Drop to 2200mbar...car runs perfect all day all night... any ideas? :-(

[RL18]

Originally Posted by Bull3t Proof

Sorry to Resurrect this....lol.

Have a N57 with L93 Fuel Pump - M50d Sensor (Scaled on map)

If i exceed 2300mbar of fuel rail pressure... WOT, car stalls everytime. Hot or Cold...

Drop to 2200mbar...car runs perfect all day all night... any ideas? :-(

Did this just happen, and your n57 was running fine before

Or did you do something and now it's stalling out

[Bull3t Proof]

Basically anything past 2300 rail pressure.care stalls

[Dex21]

Originally Posted by Bull3t Proof

Basically anything past 2300 rail pressure.care stalls

May be a bit late now but the issue with why it stalls past 2300 is that your fuel rail pressure sensor needs upgrading to one which can read past 2200 which is what the stock one can only read up to.

Darkside developments in the UK offer an upgrade.

Hope this helps anyone else with this issue