# E70 35D stall, Low Rail Pressure



## PhilClayton (Apr 9, 2019)

I have a sudden stall, crank no start situation with my e70 35d. 

Reading my rail pressure with a Foxwell 510 i'm seeing 8.7bar ignition on, rising gradually to 80bar during cranking, When I stop cranking it rapidly drops back to 8bar.

Another channel called 'required pressure' indicated 300-320 bar I presume this means I am way short of the pressure required for injection?

I also presume this means my HPFP or fuel pressure regulator valve? (is there one) is malfunctioning. 

Oddly the car is not showing any codes related to fuel pressure.

Potentially relevant codes to a stalling followed by a crank no start condition is 3ecO - crankshaft position sensor fault ie nothing to do with fuel pressure...or am I well of f the mark here. 

Any thoughts / guidance on where to look next appreciated. 

PS Tank is near full, has not been below 1/4 for a long time and have run LPFP with Foxwell and can hear it operate.


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## smokeyyy (Oct 29, 2005)

The rail pressure should be >1000 bar so if this is true, you are way off. Are you sure this is the rail pressure?

#2 is the pressure regulating valve. However, I would diagnose and make sure it is failing before replacement.

I also believe a faulty crankshaft position sensor could cause the car to not start.


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## Doug Huffman (Apr 25, 2015)

smokeyyy said:


> I also believe a faulty crankshaft position sensor could cause the car to not start.


*Don’t it make your brown eye blue? ...”

Home / BMW E70 X5 xDrive35d SAV / Wiring Diagrams and Functional Description / Power train / Diesel electronics DDE7 US / Engine speed recording / Camshaft sensor /
Engine speed detection DDE7
Two sensors are used to detect the engine speed and the position of the camshaft and the crankshaft:
[ ... ]
This process is referred to as synchronisation and is only performed when the engine is started. Effects of faults on the signals:

Camshaft sensor signal not OK: Engine can be started, but starting takes longer, no effect when engine is running
Crankshaft sensor signal not OK: Engine start via camshaft sensor signal possible with some versions; when the engine is running, the camshaft sensor signal is used and the torque is limited
*


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## Frank drebin (Jan 13, 2021)

Common rail systems require anywhere between 250-300 bar before it allows the injectors to fire and then can make towards 2000 bar when driven under load, whenever ive had a fuel rail pressure thats around 80 bar its either turned out to be restricted/ low fuel supply from tank / the fuel rail pressure sensor misreading or a single injector leaking back excessively, get a spill test done on your injectors first to see what they are returning compared to spec, if one has failed you can normally see it on test straight away it will fly ahead of the others and if the car is higher mileage sometimes the rest are not far away either replace one and the next weakest fails the joys of common rail diesels, good luck man.


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## PhilClayton (Apr 9, 2019)

Would I expect to see any low fuel pressure (low or high side) codes if I had a fuel supply issue eg restricted/ low fuel supply from tank / the fuel rail pressure sensor misreading or a single injector leaking back excessively? What would you suggest as a test sequence? Do you think I should go straight to a excess leak back test with syringes or are there some other things you would suggest to check first?

My current codes are:
4252/present/glow plug cyl 5.
4262/present/ glow plug cyl 6.
3EC0/not present/DDE camshaft sensor signal
3EC1/not present/DDE camshaft sensor signal
41f2/present/DDE Electric fan activator

53fc/present/VTG Supply control unit terminal 30
54c6/present/VTG oil wear

D36A/not present/ no message (VTG, OXBC) receiver DSG transmitter VTG
5F3A/present/DSG Transfer case malfunction


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## ard (Jul 1, 2009)

Doug Huffman said:


> Crankshaft sensor signal not OK: Engine start via camshaft sensor signal possible with *some versions;* when the engine is running, the camshaft sensor signal is used and the torque is limited


BMW means "some model cars" by their bolded 'some versions'

Also, interesting...without a crankshaft signal the DME cannot detect misfires. So a low power mode (aka 'limited torque') will be self protective.

I also seem to recall that lack of a CkPS will inhibit fuel pump? in some versions. Not sure, but seem to recall someone chasing down a 'fuel pump not running' issue.


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## PhilClayton (Apr 9, 2019)

Note code relates to camshaft and that vehicle was being driven up a moderately steep driveway (so >1000rpm) when it stalled. Seems odd that this condition would provoke a shut down due to excessive leak back. 

Noting also that the rail pressure drops rapidly back to 8bar. I had thought that rail pressure should hold in the system. Is this rapid drop after stopping cranking abnormal?


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## PhilClayton (Apr 9, 2019)

Have dived a little deeper into this over the weekend. 

Have confirmed low pressure side of fuel supply is OK with a reading of 4 bar on the low pressure side (turns out that ignition on does not run these pumps on my model, needs to be cranked too)
Used troubleshooting process in this link:
http://www.londonroadgarage.com/imag...kg&LMCL=UUXura 

Step 1: Disconnection the control-flow regulating valve - no change.
Step 2: Disconnected an reconnected pressure regulating valve - contacts clean - no change
Step 3: Check for external leaks - none
Step 4: Check for fuel in oil - no diesel smell. 
Step 5: Check setpoint for residual fuel pressure (8bar) - OK
Step 6: Check setpoint for rail pressure NG (80Bar VS 300Bar)
Step 7: Disconnect Rail pressure sensor - no start
Step 8: Fuel injector excess internal bypass.

Performed test on injector1. Could not get any bypass (<<1ml) with 15sec cranking. Lots (>>50ml) of diesel discharging from bypass hose where disconnected form Injector 1. However, when the hose was clamped downstream from where disconnected from injector 1 flow became negligible. From this I concluded that bypass from all injectors minimal and so excess injector bypass not the issue.

Where to from here?
I'm thinking that the remaining possible reasons for the issue might be:
1. Defective pressure regulator
2. Defective control flow regulating valve 
3. Defective HPFP

I don't have the special tools to blank off the HPFP to allow a pressure test. 

There is a suggestion to pull the filter - if there is any debris then assume HPFP is kaput and replace it (after cleaning the system).

Thoughts/comments/advice


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## Frank drebin (Jan 13, 2021)

Sounds like youre getting there, one thing i have tried before and should work on your car is to test what the pump can generate with regards to pressure, if i remember correctly i disconnected the electrical connector off each injector and the fuel pressure regulator just leaving rail pressure sensor connected then cranked the engine watching fuel pressure on live data and with a good pump i would see it build to 1600+ bar at which point i could rule that out, ive tried this on a lot of different diesel systems and it worked so it will hopefully work on yours.


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## PhilClayton (Apr 9, 2019)

I thought I'd pull the filter first and check for debris. Good news is that when I tipped the filter up into a glass jar pure clean diesel came out. No debris, no water, no metal flakes. Bad news is I now have to wait for a new filter as I couldn't get the old one to lock back in properly. I'd bent the aluminium tabs so the clip wouldn't go back in properly.


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## PhilClayton (Apr 9, 2019)

Would be interested to hear what some of the real brains trust on here thinks I should do next....I see from this details that @Doug Huffman has the same vehicle...


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## Doug Huffman (Apr 25, 2015)

Frank drebin said:


> Common rail systems require anywhere between 250-300 bar before it allows the injectors to fire


Never heard of such a thing. Absence of evidence is not evidence of absence.

Thanks, but the shady experts are already busy here and I will not gainsay them. I had my say in post #3


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## Frank drebin (Jan 13, 2021)

Doug common rail diesels require this pressure to be seen by the ECM or it will not attempt to run its common knowledge for those who know and ive been doing this successfully for 22 years im not just some clown posting for the sake of it.


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## ard (Jul 1, 2009)

PhilClayton said:


> Would be interested to hear what some of the real brains trust on here thinks I should do next....I see from this details that @Doug Huffman has the same vehicle...


Frank Drebin is one of them. He actually works on these cars, so very signification hands on.....


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## Doug Huffman (Apr 25, 2015)

BMW TIS Rail pressure control TROUBLESHOOTING
If the DDE detects a rail-pressure control discrepancy that is outside the permissible limits, its first action is to limit the fuel injection rate. If this does not eliminate the control discrepancy or keep it to a low level, the engine cuts out or, as the case may be, cannot be started.


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## PhilClayton (Apr 9, 2019)

Still banging my head against this one. Surely if the DDE detects a rail pressure control discrepancy it would throw a code to that effect? 

I am suspecting that my fuel pressure is being lowered by a faulty rail pressure regulating valve or a faulty control flow regulating valve.

I tried starting with the control flow regulating valve disconnected (supposed to be normally closed) but that didn't help anything. I'm wondering if I can confirm if it is actually closed when disconnected (to eliminate this being stuck open as a possible cause of the issue) by checking for flow in the return line. What I'm not sure is if there would normally be any other bypass return from the pump too even when the control flow regulating valve is closed.

Fuel lines BMW X5 E70, X5 3.0d (M57N2) â€” BMW parts catalog

What I would look to do is disconnect electrical connector to control flow regulating valve and Banjo bolt at 8/9 on diagram and look for flow during cranking.

However if there is always a fuel return from pump along this line even with control flow regulating valve closed this would not work.

Thoughts?


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## PhilClayton (Apr 9, 2019)

Frank drebin said:


> Sounds like youre getting there, one thing i have tried before and should work on your car is to test what the pump can generate with regards to pressure, if i remember correctly i disconnected the electrical connector off each injector and the fuel pressure regulator just leaving rail pressure sensor connected then cranked the engine watching fuel pressure on live data and with a good pump i would see it build to 1600+ bar at which point i could rule that out, ive tried this on a lot of different diesel systems and it worked so it will hopefully work on yours.


Hi Frank, 
Thought I should also note that I tried this procedure too. 
As you are probably aware there is a pressure regulator on the pump control flow regulating valve ) (that is normally closed (closed when disconnected and closed when fuel temp low) and a pressure regulator on the rail which is normally open (fully open when disconnected). I get no difference in the rail pressure while cranking with the pump pressure regulator (control flow regulating valve ) connected or disconnected it gradually builds to 100bar on a 5-8 second crank. When I disconnect the rail pressure regulating valve and crank the reader shows no rise in rail pressure whatsoever (perhaps indicating that the rail pressure regulating valve is wide open). I have tried this with the injectors connected and disconnected and get same result.


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## Doug Huffman (Apr 25, 2015)

Piping diagram and legend for High Pressure Fuel. If you have hacked at the injectors then they are probably toofed.


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## PhilClayton (Apr 9, 2019)

Thanks for diagram Doug. What I'm interested in is testing the performance of either the fuel rail pressure control valve (5) or the volume control valve (13) as I think I have isolated my problem to either a fault in (13), (6) or (12). As (13) is a normally closed (closed = no bypass) valve, when I disconnect electrically then it should send full (unregulated) flow from the pump to the rail. What I am trying to do is use this functionality to prove a fault in either of the (5) or (13) so I can then go and try to source a replacement (or test further to diagnose valve vs pump). My hypothesis is if there is diesel flowing from the pump return line, and if there is no other source than bypass by (13), and (13) is disconnected, hence not bypassing, then (13) is faulty. If there is no fuel flowing down the return then (6) or (12) is faulty. For this hypothesis to to work* I need to confirm there are no other possible sources of diesel making its way down the green arrow line (6) from the pump* ie an internal bypass for cooling and lubrication purposes.

This didn't seem to show one,Common Rail Injection System Pressure Control but illustration is CP1 and I understand the 35d uses a CP3?

PS - Google translate didn't recognize 'toofed' but wondering why electrically disconnecting injectors might be an issue?


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## PhilClayton (Apr 9, 2019)

Thanks for the folks who helped me with this. Turns out that I was incorrect in assuming that because I had some (albeit low) rail pressure my timing chain was intact. I pulled the can sensor and watched the cam while the engine was cranked and.....nothing. Cam not rotating. So it seems that the camchain had snapped which caused the crank no start. This explains the camshaft sensor error. 2020 Hindsight suggests this is obvious. Now I just need to figure what to do next...


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## Willisodhiambo (Oct 15, 2016)

I read your thread and thought I had found the answers to my problem but not yet! Car (E70 M57N) stalled and chain was found broken. Fixed chain (by Good mechanic) but after that it is now crank almost start first time then no start after. Fuel rail pressure behaves the same. Attempts to rise to 150mbars then drops to 8.7 then again. Never reached demanded value.

1. Replaced HPFP
2. Done all tests in ISTA.
3. Low pressure pumps working
4. No fuel from HPFP, tested by opening delivery line to rail, no fuel!! Lots of fuel on the return line though from hpfp back to the tank but none through the hpfp
5. When dde unplugged, LOTS of fuel into rail from LPFP. This proves dde is closing quantity valve in hpfp?

It seems dde is closing quantity controlled valve? Engine speed, available so crankshaft sensor ok. Never mind injectors, no fuel is getting into the rail so not bothered buy replaced 3 just to test. Then blanked all outlets from the fuel rail. No fuel pressure even with that. 

Any ideas? Am stupefied. Seems like a simple engine with a simple fuel delivery problem but alas!!


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## PhilClayton (Apr 9, 2019)

Willisodhiambo said:


> I read your thread and thought I had found the answers to my problem but not yet! Car (E70 M57N) stalled and chain was found broken. Fixed chain (by Good mechanic) but after that it is now crank almost start first time then no start after. Fuel rail pressure behaves the same. Attempts to rise to 150mbars then drops to 8.7 then again. Never reached demanded value.
> 
> 1. Replaced HPFP
> 2. Done all tests in ISTA.
> ...


So your rail pressure is only getting up to around 100Bar?
The suction valve is a 'normally closed' valve to disconnecting it should prevent the dde from opening, then only regulation is on rail valve. 
Is it possible you have air in the system somewhere that is limiting the HPFP from reaching the desired pressure?

What was the damage done by broken chain to your engine? I'm about to sell mine on no reserve auction for dismantling as it's very expensive to repair here and all quotes have assumed bent valves, broken rockers etc.


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## Willisodhiambo (Oct 15, 2016)

PhilClayton said:


> So your rail pressure is only getting up to around 100Bar?
> The suction valve is a 'normally closed' valve to disconnecting it should prevent the dde from opening, then only regulation is on rail valve.
> Is it possible you have air in the system somewhere that is limiting the HPFP from reaching the desired pressure?
> 
> What was the damage done by broken chain to your engine? I'm about to sell mine on no reserve auction for dismantling as it's very expensive to repair here and all quotes have assumed bent valves, broken rockers etc.


Chain broke at low speed so just one or two bent valves. Nothing much.

I have bled and bled again. seems. Note that when DDE is disconnected, fuel arrived in a torrent at the rail. I therefore think it is something else.

Tried disconnecting the qty control valve, no change. I am stumped.


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## PhilClayton (Apr 9, 2019)

I presume you have tried ether?


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## Willisodhiambo (Oct 15, 2016)

PhilClayton said:


> I presume you have tried ether?


Not yet. Will attempt to borrow complete fuel system from running car to see if anything changes


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## n1das (Jul 22, 2013)

PhilClayton said:


> I presume you have tried ether?


Please....DO NOT DO THIS with any diesel...EVER!! You risk a runaway engine condition followed by instant engine destruction. In diesels with glowplugs, a hot GP can ignite the ether at totally the wrong time and literally shatter pistons. Absolutely DO NOT DO this!


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## Willisodhiambo (Oct 15, 2016)

n1das said:


> Please....DO NOT DO THIS with any diesel...EVER!! You risk a runaway engine condition followed by instant engine destruction. In diesels with glowplugs, a hot GP can ignite the ether at totally the wrong time and literally shatter pistons. Absolutely DO NOT DO this!


 Caveat well taken!!


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