Reason(s) for Fuel Pump Failure

steve02492 · 04-29-2007, 06:40 AM

I am trying to understand why the same fuel pump, with the same potential defects, would fail in some cars and not others. For instance, not everyone with a 9/06 build date is experiencing problems, and some have gone many miles (I think that the record so far is 18,000 posted on this board). For those of you who understand the components inside this pump, what do you think is going on? I have some theories but would like to hear from people who actually know how these pumps work...

In the pumps that fail, what component, exactly, has failed? I have about 6400 miles on a 9/06 build 335i and no problems so far.

keithIOW · 04-30-2007, 06:58 AM

Can I have your fuel pump please

E90Fleet · 04-30-2007, 07:11 AM

Without knowing what is failing, its almost impossible

noro · 04-30-2007, 09:29 AM

1. It's a relatively new device. Regular fuel pumps don't push fuel into a 200PSI pressurized chamber

2. It could come from one or many of the bad batches of the supplier (Bosch, MANN, MAHLE etc)

iatacs19 · 04-30-2007, 09:45 AM

Do they use multiple suppliers? I guess it would be impossible to get the data as to which supplier is having the most failures, or if it is in fact a single supplier that is having all the failures.

Gort · 04-30-2007, 09:51 AM

Quote:

Originally Posted by noro

It could come from one or many of the bad batches of the supplier (Bosch, MANN, MAHLE etc)

I was under the impression that these were sole sourced from Siemens VDO.

noro · 04-30-2007, 10:39 AM

Quote:

Originally Posted by Gort

I was under the impression that these were sole sourced from Siemens VDO.

You are probably correct, I was just listing those names as suppliers in the past models.... hmmm maybe they should stick to Bosch

stressdoc · 04-30-2007, 12:07 PM

Pretty sure this is exclusively Siemens AG's baby.

DanMardik · 04-30-2007, 12:08 PM

This question has been going through my mind for a while.

Which particular part in the pump is failing and why?

treytreyfeva · 04-30-2007, 02:06 PM

My understanding is that the fuel pump actually houses 2 seperate pumps; one sucks the fuel from the gas tank, and the second pump pushes the the fuel via high pressure to the direct injection system. I hear the latter of the 2 is what is failing.

Lost Horizon · 04-30-2007, 04:06 PM

There are 2 seperate pumps, not in the same housing at all. The low pressure pump gets the fuel to the high pressure pump at a positive back pressure. The low pressure pump is electric, the High pressure is mechanically driven by the engine.

The high pressure is created by lowering the volume on the high pressure side via three rod driven bellows. Check valves keep the flow going one way, and maintain the High pressure side pressure as the bellows do their thing.

So, possible candidates for failure are:
1. the hi pressure check valve
2. the bellows or the connection/assembly to the plunger rods (x3)
3. the mechanical drive flange (less likely)

Knowing that this is gasoline we are pumping, and that it's lubricating properties are near zilch, that HP check valve needs to be self lubricating, yet tight..

While there are lots of well proven Fuel control units and hi pressure injector pumps in the diesel side of the business, the advantage they have is that fuel oil also lubricates the internal parts..

Cutting the gasoline with ethanol even makes it dryer, whether that can be statistically shown to have any relevance here is another matter.

here's a cross section of the pump, make your own call:

GS833 · 04-30-2007, 06:44 PM

This may be a stupid question ("note to self: if it sounds stupid it probably is") but are the MT and AT fuel pumps the same? Because I've heard people say that only automatics are failing, any truth to that? My car has almost 6k miles and to this day no problems...knock on wood...

Crazy Bimmer · 04-30-2007, 07:13 PM

Could it be that some owners wait till their gas light is on before filling up?

Maybe thats too much stress on the fuel pumps?

DanMardik · 04-30-2007, 07:15 PM

Quote:

Originally Posted by Crazy Bimmer

Could it be that some owners wait till their gas light is on before filling up?

Maybe thats too much stress on the fuel pumps?

Not sure, but i highly doubt it.

abdarm · 04-30-2007, 07:17 PM

i am scared of mine goign bad now- I am a may production

ironic · 04-30-2007, 07:23 PM

Quote:

Originally Posted by Crazy Bimmer

Could it be that some owners wait till their gas light is on before filling up?

Maybe thats too much stress on the fuel pumps?

no. i have never had my light come on. i only have 1600 miles too. i also only fill up from one chevron station.

and imho, if that were the case there should be a disclaimer about the pump. i'm really frustrated with all this fuel pump business, i can't enjoy my damn car.

Lost Horizon · 04-30-2007, 08:13 PM

Quote:

Originally Posted by GS833

This may be a stupid question ("note to self: if it sounds stupid it probably is") but are the MT and AT fuel pumps the same? Because I've heard people say that only automatics are failing, any truth to that? My car has almost 6k miles and to this day no problems...knock on wood...

Pumps are part of the power plant, so are identical..

Are the failures geographically diverse, or is there any pattern at all to them?

homerunball · 04-30-2007, 09:29 PM

This by no means is this supported by any specific knowledge of the HP pump-- It was suggested on this forum before that adding a tiny bit of oil with the fuel helped with BMW's diesel pumps(at even higher pressure than the current 335i). Maybe someone whos engine is showing terminal symptoms of fuel pump failure can try an experiment.

I can say that very small amounts of oil will not harm the operation of the car and any of its fuel dependent systems. It is true that modern fuel is much "dryer" and "thinner".

04-29-2007, 06:40 AM	#1
steve02492 Private 10 Rep 66 Posts Drives: 2007 335i coupe Join Date: Sep 2006 Location: Boston, MA iTrader: (0)	Reason(s) for Fuel Pump Failure I am trying to understand why the same fuel pump, with the same potential defects, would fail in some cars and not others. For instance, not everyone with a 9/06 build date is experiencing problems, and some have gone many miles (I think that the record so far is 18,000 posted on this board). For those of you who understand the components inside this pump, what do you think is going on? I have some theories but would like to hear from people who actually know how these pumps work... In the pumps that fail, what component, exactly, has failed? I have about 6400 miles on a 9/06 build 335i and no problems so far.
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04-30-2007, 06:58 AM	#2
keithIOW Second Lieutenant 19 Rep 222 Posts Drives: E93 325 SE Join Date: Oct 2006 Location: Isle of Wight, U.K. iTrader: (0)	Can I have your fuel pump please __________________ E93 325 SE, Sparkling Graphite, Black Dakota, hi-gloss black trim, 230's, Folding Mirrors, C/A, Sat Nav, Sport Seats, Front Seat Heating, prof Hi-Fi
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04-30-2007, 07:11 AM	#3
E90Fleet Lieutenant General 1312 Rep 10,185 Posts Drives: BMW Join Date: Apr 2005 Location: South Africa iTrader: (0)	Without knowing what is failing, its almost impossible __________________ BMW if you are reading, I need a job, Please.
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04-30-2007, 09:29 AM	#4
noro Colonel 90 Rep 2,707 Posts Drives: '91 M3, '04 E46 ZHP, '72 2002 Join Date: Aug 2006 Location: Boston iTrader: (0)	1. It's a relatively new device. Regular fuel pumps don't push fuel into a 200PSI pressurized chamber 2. It could come from one or many of the bad batches of the supplier (Bosch, MANN, MAHLE etc) __________________ zhpregistry.net - ZHP stats and free classifieds.
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04-30-2007, 09:45 AM	#5
iatacs19 Major General 459 Rep 5,319 Posts Drives: 2016 SO M4 Join Date: Sep 2006 Location: Washington, DC iTrader: (8)	Do they use multiple suppliers? I guess it would be impossible to get the data as to which supplier is having the most failures, or if it is in fact a single supplier that is having all the failures.
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04-30-2007, 12:07 PM	#8
stressdoc Moderator 618 Rep 10,855 Posts Drives: BMW i8; Toy 4runner TRD pro Join Date: Jun 2005 Location: Waco TX iTrader: (0)	Pretty sure this is exclusively Siemens AG's baby. __________________ My recent ED photos: http://f80.bimmerpost.com/forums/sho....php?t=1026808 my not-so-recent ED: http://www.e90post.com/forums/showthread.php?t=31829 Please join BMWCCA http://bmwcca.org/index.php?pageid=c...&ref_by=300279
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04-30-2007, 12:08 PM	#9
DanMardik Captain 17 Rep 729 Posts Drives: 08 INFINITI G37S Join Date: Dec 2006 Location: Irvine, CA iTrader: (0)	This question has been going through my mind for a while. Which particular part in the pump is failing and why? __________________ *RIP 2007 335i Sedan*
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04-30-2007, 02:06 PM	#10
treytreyfeva Puro Pinche Party! 23 Rep 133 Posts Drives: 2007 E90 335i TiAG Join Date: Mar 2007 Location: SFV818 iTrader: (1)	My understanding is that the fuel pump actually houses 2 seperate pumps; one sucks the fuel from the gas tank, and the second pump pushes the the fuel via high pressure to the direct injection system. I hear the latter of the 2 is what is failing.
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04-30-2007, 04:06 PM	#11
Lost Horizon Captain 29 Rep 633 Posts Drives: 435 MPPK+1970 XKE OTS Join Date: Oct 2006 Location: Victoria BC iTrader: (0)	There are 2 seperate pumps, not in the same housing at all. The low pressure pump gets the fuel to the high pressure pump at a positive back pressure. The low pressure pump is electric, the High pressure is mechanically driven by the engine. The high pressure is created by lowering the volume on the high pressure side via three rod driven bellows. Check valves keep the flow going one way, and maintain the High pressure side pressure as the bellows do their thing. So, possible candidates for failure are: 1. the hi pressure check valve 2. the bellows or the connection/assembly to the plunger rods (x3) 3. the mechanical drive flange (less likely) Knowing that this is gasoline we are pumping, and that it's lubricating properties are near zilch, that HP check valve needs to be self lubricating, yet tight.. While there are lots of well proven Fuel control units and hi pressure injector pumps in the diesel side of the business, the advantage they have is that fuel oil also lubricates the internal parts.. Cutting the gasoline with ethanol even makes it dryer, whether that can be statistically shown to have any relevance here is another matter. here's a cross section of the pump, make your own call: Last edited by Lost Horizon; 04-30-2007 at 08:38 PM..
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04-30-2007, 06:44 PM	#12
GS833 Lieutenant 24 Rep 421 Posts Drives: 330i ZHP Join Date: Jul 2006 Location: San Marcos, CA iTrader: (1)	This may be a stupid question ("note to self: if it sounds stupid it probably is") but are the MT and AT fuel pumps the same? Because I've heard people say that only automatics are failing, any truth to that? My car has almost 6k miles and to this day no problems...knock on wood... __________________ Formerly know as 330iE90 2004 330i ZHP 2006 United Grey GTI (wife's) - DSG, package 1. 1974 Chamonix 2002tii - (SOLD)
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04-30-2007, 07:13 PM	#13
Crazy Bimmer The Jesal 391 Rep 5,859 Posts Drives: E90 M3 Join Date: Nov 2005 Location: Chicago IL iTrader: (20) Garage List 2009 BMW M3 [0.00]	Could it be that some owners wait till their gas light is on before filling up? Maybe thats too much stress on the fuel pumps? __________________ 2009 E90 M3 - SOLD
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04-30-2007, 07:17 PM	#15
abdarm Private 20 Rep 61 Posts Drives: 335i Join Date: Apr 2007 Location: San Diego iTrader: (0)	i am scared of mine goign bad now- I am a may production __________________ e92 335i-step black sapphire/ saddle brown sport/premium/comfort/nav
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04-30-2007, 09:29 PM	#18
homerunball Private 0 Rep 81 Posts Drives: 96 Geo Metro 1.0L Join Date: Dec 2006 Location: Los Angeles iTrader: (0)	This by no means is this supported by any specific knowledge of the HP pump-- It was suggested on this forum before that adding a tiny bit of oil with the fuel helped with BMW's diesel pumps(at even higher pressure than the current 335i). Maybe someone whos engine is showing terminal symptoms of fuel pump failure can try an experiment. I can say that very small amounts of oil will not harm the operation of the car and any of its fuel dependent systems. It is true that modern fuel is much "dryer" and "thinner". Last edited by homerunball; 04-30-2007 at 11:09 PM..
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