E70 X5 3.0d cranking but no start after fuel pressure sensor
Discussion
Full title! E70 X5 3.0d cranking but no start after fuel pressure sensor change
Hi all
I can see from various forum searches that I’m far from the first person with this problem, but so far I haven’t found any definitive answers online so apologies for yet another thread on this subject and the long post.
Due to a couple of random instances of engine shut down (no faults showing) I changed the fuel rail pressure sensor. Online videos and the ISTA repair instruction show this as a straight swap, other than the ISTA requiring a reset of the quantity mean value adaption (MMA) for Euro 4 cars via the ISTA service function.
I used a 2nd hand sensor from eBay which was part of a complete fuel rail (no info on if the sensor worked), fitted it and ran the MMA reset.
Engine cranked over but didn’t fire and the fault code 004B90 DDE rail pressure monitoring on engine start (or 3F30 on a handheld scanner) was now showing. Swapped back to the original sensor, cleared the fault and still not starting.
So far, I have tried:
MMA reset, fault code clearance
1x fuel system bleed with ISTA - could hear the low-pressure pump and low pressure on ISTA was above the target. I think this also generated another pressure sensor code fault along the lines of rail pressure on changeover but haven’t had that one since this test.
There is about 0.5V on the sensor signal when fitted and powered up. This voltage doesn’t really change when the engine is cranked and should be in the 1v range, I think. I’ve checked the wiring to the DDE from the plug by applying a voltage – this registered a change in fuel pressure.
Both sensors have similar unpowered resistance levels between 5v to Gnd, Signal to 5v and signal to ground (in this case >200MOhm
I ran through another ISTA diagnostics process which failed at the engine start but showed a slight increase in rail pressure (from 6.5 to 8.7 bar but well below the 250bar minimum). The procedure also included trying a start with the connector off the pressure sensor (car reverts to a preset pressure demand mode I think) – still no start.
It’s worth noting that I had to remove the eBay sensor from the rail with the help of hammer taps to the spanner due to the torque needed to free it. The original sensor fitted to the car needed similar use of a hammer, but with less force to free it. There are no visible fuel leaks around the sensors when refitted and start is attempted.
So, it seems I have either screwed up 2 sensors or for some reason (air in the system?) there’s insufficient fuel pressure to the rail.
Can anyone who has solved this please help or offer suggestions for next steps?? It would be much appreciated!
Hi all
I can see from various forum searches that I’m far from the first person with this problem, but so far I haven’t found any definitive answers online so apologies for yet another thread on this subject and the long post.
Due to a couple of random instances of engine shut down (no faults showing) I changed the fuel rail pressure sensor. Online videos and the ISTA repair instruction show this as a straight swap, other than the ISTA requiring a reset of the quantity mean value adaption (MMA) for Euro 4 cars via the ISTA service function.
I used a 2nd hand sensor from eBay which was part of a complete fuel rail (no info on if the sensor worked), fitted it and ran the MMA reset.
Engine cranked over but didn’t fire and the fault code 004B90 DDE rail pressure monitoring on engine start (or 3F30 on a handheld scanner) was now showing. Swapped back to the original sensor, cleared the fault and still not starting.
So far, I have tried:
MMA reset, fault code clearance
1x fuel system bleed with ISTA - could hear the low-pressure pump and low pressure on ISTA was above the target. I think this also generated another pressure sensor code fault along the lines of rail pressure on changeover but haven’t had that one since this test.
There is about 0.5V on the sensor signal when fitted and powered up. This voltage doesn’t really change when the engine is cranked and should be in the 1v range, I think. I’ve checked the wiring to the DDE from the plug by applying a voltage – this registered a change in fuel pressure.
Both sensors have similar unpowered resistance levels between 5v to Gnd, Signal to 5v and signal to ground (in this case >200MOhm
I ran through another ISTA diagnostics process which failed at the engine start but showed a slight increase in rail pressure (from 6.5 to 8.7 bar but well below the 250bar minimum). The procedure also included trying a start with the connector off the pressure sensor (car reverts to a preset pressure demand mode I think) – still no start.
It’s worth noting that I had to remove the eBay sensor from the rail with the help of hammer taps to the spanner due to the torque needed to free it. The original sensor fitted to the car needed similar use of a hammer, but with less force to free it. There are no visible fuel leaks around the sensors when refitted and start is attempted.
So, it seems I have either screwed up 2 sensors or for some reason (air in the system?) there’s insufficient fuel pressure to the rail.
Can anyone who has solved this please help or offer suggestions for next steps?? It would be much appreciated!
Fair comment re the part swap, but in order to have a reasonable length post, I missed out some background which is that on the two or three occasions the car died when running it wouldn't restart straightaway. Needed 10 or 15 minutes to recover then started. Of course when these happened, I had no diagnostics kit on me.
The last event which led to the change resulted in an RAC call out. The recovery technician who looked at the car found the following codes - 4B1C Fuel filter heater and 4460 Injector cyl 6 negative side short circuit to positive. The car did get restarted (the exact sequence of events is hazy as that was about 6 weeks ago) but he suggested a change of the fuel rail pressure sensor would be a good place to start on the intermittent fault. (Hindsight is a wonderful thing as this doesn't seem great advice as I type it.) The car did restart after he cleared the fault codes. Hence my heroic and possibly ill advised change of component.
Whilst a possible cause of the shutdown (I guess) these fault codes are no longer present. (4B1C and 4460)
I haven't checked for a crank/cam signal yet (will need to find out how) but there are no error codes reflecting an issue other than the pressure sensor on start error code.
The car was starting OK prior to me changing the rail pressure sensor - which is the only change I've made
The last event which led to the change resulted in an RAC call out. The recovery technician who looked at the car found the following codes - 4B1C Fuel filter heater and 4460 Injector cyl 6 negative side short circuit to positive. The car did get restarted (the exact sequence of events is hazy as that was about 6 weeks ago) but he suggested a change of the fuel rail pressure sensor would be a good place to start on the intermittent fault. (Hindsight is a wonderful thing as this doesn't seem great advice as I type it.) The car did restart after he cleared the fault codes. Hence my heroic and possibly ill advised change of component.
Whilst a possible cause of the shutdown (I guess) these fault codes are no longer present. (4B1C and 4460)
I haven't checked for a crank/cam signal yet (will need to find out how) but there are no error codes reflecting an issue other than the pressure sensor on start error code.
The car was starting OK prior to me changing the rail pressure sensor - which is the only change I've made
Edited by Air Support on Friday 31st March 21:49
Edited by Air Support on Friday 31st March 23:54
I had an e53 that would die with fuel pressure codes, it was an intermittantly failing side transfer pump, with half a tank of fuel it would only pick up from one side of the tank and run out of fuel even though the other half of the tank was full. With a full tank it was fine. Simple test, try filling the tank right up if its not.
This will make it harder if you need to drop the tank but on the e53 you could acces the lift pump and sender from the back seats.
How are you measuring rail sensor voltage? Backprobing the plug or at the ecu? There could be a broken wire or corroded connector between them.
Last bmw I ever had, sick of the constant faults and rust on every single one of them, never looked back. I have had far more reliable french and italian motors than bmws.
This will make it harder if you need to drop the tank but on the e53 you could acces the lift pump and sender from the back seats.
How are you measuring rail sensor voltage? Backprobing the plug or at the ecu? There could be a broken wire or corroded connector between them.
Last bmw I ever had, sick of the constant faults and rust on every single one of them, never looked back. I have had far more reliable french and italian motors than bmws.
Edited by OldGermanHeaps on Saturday 1st April 10:33
Firstly, thanks both for commenting
No other changes made, just the fuel pressure sensor and car was starting before the change
Crank speed seems normal
Haven't tried easy start (actually don't have any!) - can get some if likely to help of course
Re the voltage, I've been back probing as far back into the loom from the front as I can access, so away from the connector. I did unplug the connector and applied a voltage from an automotive voltage generator back into the cable, With this I was able to vary the DDE actual pressure reading from 5bar to 400 bar, so I don't think the cabling is the issue.
Seems most likely lack of fuel supply which I thought might be due to air in the system, hence running the bleed process. The Ista repair instruction doesn't show that as being necessary for the part change though.
The low pressure pump is making the required pressure on test so i guess this rules out a current transfer pump issue? (Might be the intermittent issue of course). There is currently just over a quarter tank of fuel in the car.
I haven't looked at the clear piece of pipe running fuel into the engine bay for fuel flow but will do that once i have someone with me to press the start button.
Thanks again for your thoughts
stevieturbo said:
Is pressure making target ?
What else did you disturb when in there changing the part ?
What sort of rpm's is it cranking at ?
If you spray a little easy start in will it start ?
Pressure as shown by ISTA is going to max 8 bar if we assume the sensor is working correctly, demand pressure was normal c. 320 demandedWhat else did you disturb when in there changing the part ?
What sort of rpm's is it cranking at ?
If you spray a little easy start in will it start ?
No other changes made, just the fuel pressure sensor and car was starting before the change
Crank speed seems normal
Haven't tried easy start (actually don't have any!) - can get some if likely to help of course
OldGermanHeaps said:
How are you measuring rail sensor voltage? Backprobing the plug or at the ecu? There could be a broken wire or corroded connector between them.
Good to know the quality of French cars has improved since my early days in Renaults!Re the voltage, I've been back probing as far back into the loom from the front as I can access, so away from the connector. I did unplug the connector and applied a voltage from an automotive voltage generator back into the cable, With this I was able to vary the DDE actual pressure reading from 5bar to 400 bar, so I don't think the cabling is the issue.
Seems most likely lack of fuel supply which I thought might be due to air in the system, hence running the bleed process. The Ista repair instruction doesn't show that as being necessary for the part change though.
The low pressure pump is making the required pressure on test so i guess this rules out a current transfer pump issue? (Might be the intermittent issue of course). There is currently just over a quarter tank of fuel in the car.
I haven't looked at the clear piece of pipe running fuel into the engine bay for fuel flow but will do that once i have someone with me to press the start button.
Thanks again for your thoughts
My transfer pump issues were intermittant, and mostly when my mrs was driving and in an already bad mood.
Testing with a simulator usually only checks the signal wire, could also be supply or ground wire high resistance/open.
Tbf my bmws were all over 100k miles, but they always had more unusual and difficult to trace than anything else of a similar complexity and age.
Any other wiring disturbed? Might be something else stopping the lift pump when cranking.
Testing with a simulator usually only checks the signal wire, could also be supply or ground wire high resistance/open.
Tbf my bmws were all over 100k miles, but they always had more unusual and difficult to trace than anything else of a similar complexity and age.
Any other wiring disturbed? Might be something else stopping the lift pump when cranking.
Edited by OldGermanHeaps on Saturday 1st April 14:03
OldGermanHeaps said:
Testing with a simulator usually only checks the signal wire, could also be supply or ground wire high resistance/open.
Any other wiring disturbed? Might be something else stopping the lift pump when cranking.
Re the simulator test, doesn't the change in measured pressure as the voltage is increased suggest this is all working OK? Any other wiring disturbed? Might be something else stopping the lift pump when cranking.
I think you are suggesting a check of all three wires from the connector back to DDE is the better check? Certainly checking at the connector seems to show a good 5v and ground and there can't be much current drawn when the fuel pressure sensor is operating.
Or do you mean the lift pump wiring perhaps?
Re any other wiring - nothing else disturbed and so far I haven't gone anywhere near any fuel pumps!
Air Support said:
Good to know the quality of French cars has improved since my early days in Renaults!
Re the voltage, I've been back probing as far back into the loom from the front as I can access, so away from the connector. I did unplug the connector and applied a voltage from an automotive voltage generator back into the cable, With this I was able to vary the DDE actual pressure reading from 5bar to 400 bar, so I don't think the cabling is the issue.
Seems most likely lack of fuel supply which I thought might be due to air in the system, hence running the bleed process. The Ista repair instruction doesn't show that as being necessary for the part change though.
The low pressure pump is making the required pressure on test so i guess this rules out a current transfer pump issue? (Might be the intermittent issue of course). There is currently just over a quarter tank of fuel in the car.
I haven't looked at the clear piece of pipe running fuel into the engine bay for fuel flow but will do that once i have someone with me to press the start button.
Thanks again for your thoughts
Exactly what pressure sensor is this ? Common rail diesels run at hundreds of bar, not 8 bar. Nor should the sensor max out at any time, or indeed any sensor.Re the voltage, I've been back probing as far back into the loom from the front as I can access, so away from the connector. I did unplug the connector and applied a voltage from an automotive voltage generator back into the cable, With this I was able to vary the DDE actual pressure reading from 5bar to 400 bar, so I don't think the cabling is the issue.
Seems most likely lack of fuel supply which I thought might be due to air in the system, hence running the bleed process. The Ista repair instruction doesn't show that as being necessary for the part change though.
The low pressure pump is making the required pressure on test so i guess this rules out a current transfer pump issue? (Might be the intermittent issue of course). There is currently just over a quarter tank of fuel in the car.
I haven't looked at the clear piece of pipe running fuel into the engine bay for fuel flow but will do that once i have someone with me to press the start button.
Thanks again for your thoughts
stevieturbo said:
Exactly what pressure sensor is this ? Common rail diesels run at hundreds of bar, not 8 bar. Nor should the sensor max out at any time, or indeed any sensor.
Yes, that's exactly the point. It's the rail fuel pressure sensor which when the car was working was reading about 320 bar.Since the change and refit of the original sensor it's not showing more than about 8 bar on cranking, 6 bar when sitting with the ignition on,
Either I've managed to damage the sensor when removing and then refitting or the removal has caused an issue where the car no longer generates sufficient fuel pressure on cranking due to fuel supply issues, which I think is most likely as I believe the wiring back to the DDE from the sensor is OK.
Additionally, I worked through a fault diagnosis on the ISTA which requested that after a non-start with the pressure sensor connected to try for a start attempt with it disconnected, as the DDE should default to a pre-determined setting, but again the car wouldn't start in this mode.
Hence my view of fuel or airlocking issues.
I thought I should update this thread as I did eventually get the car going.
In the end I tried a second used rail pressure sensor and monitored the rail pressure when cranking. After about 4 good cranks I noticed the rail pressure was starting to rise so I carried on cranking with the help of the battery on a second car. It took a further 4 long cranks to start but is now starting OK.
So I'm not sure if I damaged the original and first used pressure sensor I had when I removed them (and I'm not about to swap back to find out) or whether I just hadn't cranked the car sufficiently when I swapped the original pressure sensors over. Either way if changing the pressure sensor, be prepared for a lot of starting attempts to get the car started after changing the part - probably seven or eight in total.
Sadly, the stalling fault remains which seems to be due to the activation of the cylinder 6 fuel injector (fault code 4460) but I'll look at that and see what is already on here and elsewhere in terms of solutions.
Thanks again to those of you who provided advice.
In the end I tried a second used rail pressure sensor and monitored the rail pressure when cranking. After about 4 good cranks I noticed the rail pressure was starting to rise so I carried on cranking with the help of the battery on a second car. It took a further 4 long cranks to start but is now starting OK.
So I'm not sure if I damaged the original and first used pressure sensor I had when I removed them (and I'm not about to swap back to find out) or whether I just hadn't cranked the car sufficiently when I swapped the original pressure sensors over. Either way if changing the pressure sensor, be prepared for a lot of starting attempts to get the car started after changing the part - probably seven or eight in total.
Sadly, the stalling fault remains which seems to be due to the activation of the cylinder 6 fuel injector (fault code 4460) but I'll look at that and see what is already on here and elsewhere in terms of solutions.
Thanks again to those of you who provided advice.
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