E70 35D Stall while driving crank no start

[Phil C]

Originally Posted by ard

I seem to recall the DME will not activate the fuel pump if it sees no crank signal...

ARD, note that the code I read was translated by the Foxwell BMW software as Camshaft position not Crankshaft position.

Does that make a difference to your comment above. Is there any chance that the Camshaft position sensor being I/O might cause the DME to suppress the HPFP pressure?

[ard]

Ive posted about this elsewhere.... and have quite a bit of experience with this in the E39M5 V8s


You need to understand HOW an error is detected..... You have a sensor that sends a signal to the DME. It is perhaps a sin wave or other kind of varying electrical signal. IT IS NOT a text message or an email, or an encoded diagnosis. SImply put the DME needs to decide if the data is good OR if the sensor has failed or if the data cannot be believed.... So if a sensor dies- open circuit. Dead short, Etc. Easy. Maybe the DME says 'sensor fault' or it says "improbable value".


But more troubling is how does the DME make sense of 5 sensor streams- crannk and two inlet and two outlet cams (for a y8 w two banks)- when all of them come in with some kind of timing arrangement and all of them looking, mostly, OK?

Which one is 'valid'? Which isnt?


Combine this with thet fact that camshat timing can vary with a vanos.



So...the crank is primary- it controls firing,injection, and sets the relative timing for the cams.


If there isnt a Crank signal, I **think** the DME says 'well we need that to run so dont pump fuel". If however, the crank signal is glitchy, maybe the DME 'sees' an error on a cam sensor that REALLY is due to an intermittant Crank error?



There have been hundreds if not thousands of reports of issues with vanos solenoids and camshaft sensors 'tripping' concomitant crank errors. But never (to my recollection) a CPS (camshaft) sensor leading to fuel pump inhibition.




anyway, I see you have an active thread on BF too? Ill prolly just stick with it there... and Frank actual turns wrenches....FWIW.



https://www.bimmerfest.com/threads/c...#post-13533797

[Clavurion]

Have you already removed cam sensor and checked if the cams are turning when engine is cranked?

[Mistercamp]

Again, you should really check your camshaft sensor (mistyped crankshaft instead of camshaft, my bad) as you have logged a code for it and a bad sensor can 100% cause a no start condition. At least rule it out. Fairly certain it will restrict fueling which is why you wouldn't see correct rail pressure.

[Clavurion]

Originally Posted by Mistercamp

Again, you should really check your camshaft sensor (mistyped crankshaft instead of camshaft, my bad) as you have logged a code for it and a bad sensor can 100% cause a no start condition. At least rule it out. Fairly certain it will restrict fueling which is why you wouldn't see correct rail pressure.

A failed cam sensor could explain non start but it's only used during start and if fails while engine is running doesn't cause anything. So unfortunately this scenario more likely points to broken lower timing chain. HPFP is not running causing low rail pressure and as the cams are not turning causes the code for camshaft sensor.

[Phil C]

Originally Posted by Clavurion

A failed cam sensor could explain non start but it's only used during start and if fails while engine is running doesn't cause anything. So unfortunately this scenario more likely points to broken lower timing chain. HPFP is not running causing low rail pressure and as the cams are not turning causes the code for camshaft sensor.

Thanks for your thoughts, however i'm assuming that if i'm getting 80-100 bar on the HPFP I don't have a broken chain.

Having tried all the other suggestions received above (thanks all) 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) 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.

Anyone have any thoughts on this?

Fuel lines BMW X5 E70, X5 3.0d (M57N2) — 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?

[Clavurion]

Always during start and during running when coolant temp under 19 C flow control valve is fully closed (max flow to pump, no leak off from flow control valve) and pressure control is done by pressure regulator at the rear end of fuel rail.

https://www.pss-autosoft.net/diagram..._FBDDE6RDR.htm

[Phil C]

Originally Posted by Clavurion

Always during start and during running when coolant temp under 19 C flow control valve is fully closed (max flow to pump, no leak off from flow control valve) and pressure control is done by pressure regulator at the rear end of fuel rail.

https://www.pss-autosoft.net/diagram..._FBDDE6RDR.htm

Thanks for that. Do you happen to know if there is an internal bypass in the pump eg for cooling that will also be discharging into the return line? What I was hoping to do is to diagnose a non-closing flow control regulating valve by checking for discharge to the fuel return line while the valve is electrically disconnected.