Would anyone be able to suggest what might be causing low pre supply pressure to be logged regularly on my 330d.
The car is remapped with egr delete, decatted and has done 155k miles now.
Full service history and has been serviced recently which included fuel filter.
I did a bit of digging and found that this code can be caused as a rule by the pump under the passenger floor. I replaced this but it made no difference sadly.
Had the tank pump out and the strainer is like new, and definitely not clogged in the slightest.
Various rpms between 2k and 4k it will log this code, but at idle i do know that it maintains the (what i believe to be correct) 4bar pressure.
The codes tend to imply that pressure drops to around the 3.5bar mark :-s
I have ordered a replacement sensor for the filter, from a breaker but im not convinced it will cure it :-/
Does anyone know if it could be signs of the in-tank pump on the way out, or maybe even the high pressure pump on the engine?
A? No, you said the code says 'pre-supply' pressure so it isn't going to be the injection pump .
It'll either be the tank pump or the sensor, either take a gamble with the sensor (cheaper & easier to change than the tank pump!) or get someone to hook a pressure gauge to the LP side & see if the sensor is right or not.
The high pressure pump was kind of a stab in the dark, thought I would mention it on the off-chance it could of been a possibility.
What about an injector, could that cause it if it was returning lots of fuel to the tank rather than injecting it say? (or something along those lines)
My worst injector (no5) is compensating at around +3 on the smooth running, I read that if this is the case for cyl 5 or 6, that you should swap it for another injector which is giving the most opposite deviation in readings, then re-test the smooth running... I presume it makes some difference due to 5 and 6 being the furtherest away from the HP pump?
I'm happy to change the in-tank pump now if it needs it, thought it would be a nightmare but removed it the other day to check the strainer was clear and it was dead easy to remove!
Rear seat base out, unscrew the cover, disconnect the electrical plug and diesel pipe, then just tap the metal ring around with a hammer anti-clockwise to remove it, and it lifts straight out. I was half expecting to have to drop the fuel tank!
I've got a replacement sensor from a breaker today so i'll give you an update after I change this!
Replacement sensor is now installed, error codes cleared and at idle the pre-supply pressure is still 4.1 bar... I will find out tomorrow after I've driven it if theres any improvement and post an update.
Yea you need to rev it up & check the sensors reading to see if you've fixed it.
Injectors are on the HP side of the system, again that won't give you a pre-supply aka LP side fault code.
Distance from the pump makes no significant difference to smooth running/pressure, they are saying swapping the injector with the most opposite deviation as a diagnostic step, to be able to clearly see if the fault has moved with the injector. But it's probably a lot easier to just do a leak off test. Usually (but not always) the leak off test will show any dodgy injectors (it won't show any spray pattern problems though).
If you don't have any smooth running fault codes or starting problems I wouldn't worry about the '+3' on an injector..... unless it's near the limit?
I think the recommended limit to change or recon the injector is +4, it starts fine and is smooth, i had to change no 4 injector for a new one when i got it about 4 months ago. It felt and sounded like a petrol misfire at low rpms but was fine under load. That injector show almost zero compensation which would make sense. Did not have to calibrate it either as i don't think the 184bhp require it, so that was a bonus!
I wonder why they say only to swap if it is cyl 5 or 6 though? Was tempted the get the garage to swap them after seeing no4 come out with so little effort.
Will try it tomorrow and check the codes again too.
So I've done some further logging today and unfortunately the sensor made no difference. Pre supply pressure still shows that its low, and its still logging fault codes for that.
I'm tempted to pickup a s/h in-tank pump and swap it... What would the symptoms of a failing in-tank pump be? It starts fine.
if you have put a new pump in they can take a lot of cranking to get going, as there is no bleed off point on the common rail fuel system as the fuel delivery pressures are massive sounds silly but make sure there is enough fuel in the tank and turn the ignition on and off at least half a dozen times before you try cranking it over so the pumps can prime the fuel system up to full pressure.
Thanks again Assimilator1, I will have a read through those 2 docs
Kink in one of the pipes is a good call, I may wait till I have it in the garage again to check that whilst its on the ramp.
With regards to starting it after changing the pump... this was no problem as I just left the ignition on for a minute to allow it to bleed itself, started up straight away. Ive Never had any issues starting it in fact... I know thats tempting fate! Lol.
Does anyone know any good bmw specialists around the devon area that would be good with fuel pressure issues?
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
BMW Forums : BimmerForums
1.5M posts
270.5K members
Since 2007
A forum community dedicated to BMW owners and enthusiasts. Come join the discussion about performance, modifications, troubleshooting, M series, motorsports, maintenance, and more!