fuel pressure question

[jfoj]

Originally Posted by trader4

Stay in your chair and open a high school science book. Your lack
of grounding in basic science is shocking. If there was no vacuum in that
intake plumbing between the throttle body and air filter, then a crack
in the intake boot/elbow would not SUCK IN AIR and cause lean codes.
It does suck in air and everyone familiar with cars reading this knows it.
It's very, very, basic physics. The vacuum present decreases as you
mover from the throttle body towards the air filter. It's how fluids
flow through pipes, ducts etc. Without a pressure gradiant along
the pipe, the fluid would not move. The vacuum or pressure will
slowly decrease along the length of the pipe. Even your local plumber
knows how this works, it's what makes water flow through pipes.

And one more time, if there were no vacuum present, then the
purpose that's stated in the reference you provided for the line from
the fuel pressure regulator would also not work.

Hey genius, go out and connect a vacuum gauge to the intake boot and report back what you find.

I'll be waiting.

[1iwilly]

to me a softfail fuel pump means like my friends scion when is cold it starts on a dime after warm up if you shut it off it won't start you have to wait until fuel pump cools down the it starts with out fail
also i don't have a maybe start maybe not since the problem it starts on a dime a pump either works or not there is no in between which would be it work but the pressure would have to drop been the brushes are worn and not making good contact

Originally Posted by jfoj

@1iwilly

99% your vehicle has a soft failed fuel pump, I have seen MANY of these and have seen your exact same situation.

There could be a fuel level sender problem or a sucking jet pump problem, however, these are highly unlikely.

Forget about testing fuel pressure here for a few reasons. First due to the age of the vehicle/fuel pump and also due to the fact that static pressure at rest or idle is very misleading, you would also need to verify fuel volume as well.

But the simplest test which does not require you do get under the hood or get dirty is watch the fuel levels via the Hidden OBC Menu. Below 1/2 tank the passenger/right side of the tank should always have more fuel than the drivers/left side with the exception of a hard right turn sloshing fuel into the drivers/left side of the tank, but it should quickly be pumped back down by the sucking jet pump.

Replace the fuel pump and your problem will be resolved.

[1iwilly]

well actually the other hose that comes from the vaccum valve for the brake booster has constant vaccum which sits atop the fprg hose not high but it is steady vaccum

Originally Posted by jfoj

Get out of your chair, go out and pull the hose from the port on the intake boot. Use for finger or a vacuum gauge and tell me how much "vacuum" is present at this connection, there will be none. You could also hook up your fuel pressure gauge and see there is not change in fuel pressure when the hose is removed.

And why you all want to argue, MOST other vehicles with vacuum operated Fuel Pressure Regulators have Manifold vacuum and went the "vacuum" hose is removed from the fuel pressure regulator the fuel pressure increases. This is not how the M54 is configured and you do not even believe what the BMW documentation states.

So until you bother to do you homework you are just wasting your time and other peoples. But this is what you apparently like to do with your time from what I can see.

OP, sorry your thread has turned into a crapfest, I am at least trying to help you and providing you with accurate information.

[jfoj]

Originally Posted by 1iwilly

to me a softfail fuel pump means like my friends scion when is cold it starts on a dime after warm up if you shut it off it won't start you have to wait until fuel pump cools down the it starts with out fail
also i don't have a maybe start maybe not since the problem it starts on a dime a pump either works or not there is no in between which would be it work but the pressure would have to drop been the brushes are worn and not making good contact

Not sure what you are stating, seems around her some call a cow a duck?

99% your fuel pump is on the way out, there can be many symptoms of soft failing fuel pumps. BMW pumps, Piersburg and Siemens/VDO seem to wear the brushes and often a few of the windings do not make good contact when running and the pump volume drops. This is one version of a soft fail pump.

As I stated, all you have to do is watch your fuel level in both tanks, the passenger/right side should never be lower then the drivers side. Most pumps have a 5000-6000 run lifespan. Keep in mind that the pump lifespan has NOTHING to do with mileage, it is all about run hours. For every second the engine is running, while you are stopped at a traffic light, stop sign, drive-thru or in stop and go traffic you are not accumulating miles, you are accumulating hours.

There are 2 extremes for vehicle users, Highway Warrior and City/Urban Dweller. A Highway Warrior may have over 150k miles for the same run hours a City/Urban Dweller may have with 75k miles. My 2006 E46 fuel pump failed at 84k miles, her car is a City/Urban Dweller. The Average MPH for most fuel fills is less than 20.

If I owned your vehicle, knowing what I know about Piersburg and Siemens/VDO fuel pumps, I would not think twice about purchasing a fuel pump.

[jfoj]

Originally Posted by 1iwilly

well actually the other hose that comes from the vaccum valve for the brake booster has constant vaccum which sits atop the fprg hose not high but it is steady vaccum

If your set up has the F connector on the top of the the intake boot, the larger hose is for the Sucking Jet Pump which is a vacuum amplifier for the power brake booster.

What you are seeing at this intake air for the Sucking Jet Pump. This is normal and again, this pickup is a "Filtered Air Input" to the Sucking Jet Pump.

There is no appreciable "Vacuum" at this F connector because there is no restriction, assuming the air filter does not weight 10 lbs. The F connector opens up in the huge cavern and then has a large low restriction air filter.

Here is a cut away of the Sucking Jet Pump so you can see it is a venturi device that is constantly bleeding a small amount of air.

BTW this input air is added and measured by the MAF which compensates for this small air bleed.

How does the BMW E39 sucking jet pump (aka suction jet pump) work & how does it fail? - Bimmerfest - BMW Forums

[jfoj]

Originally Posted by trader4

The experiment that confirms there is a vacuum in the intake system in the entire
path between the air intake near the radiator and the throttle body is done every day.
The car runs by drawing air through the intake, from the opening near the radiator,
through the air filter, through the intake ducting including the famous boot/
elbow, through the throttle body, through the intake manifold and into the
cylinders. Vacuum exists through that entire path. It's what moves the
air. Even a grade school student can understand that.

QED 1

It's also confirmed by the experiment that Upallnight first brought up
to you. When that rubber intake boot/elbow cracks, air gets sucked
in through the crack, instead of being drawn through the filter and MAF,
causing the engine to run lean and throw lean codes. If you don't believe
it, take a smoke stick and hold it near a cracked intake boot/elbow.
The smoke is drawn in, confirming a vacuum is present. And no, I'm
not going to go do it to confirm what everyone here already knows.

QED 2

It's really very basic science. The air moves through the intake
system by a pressuse drop gradiant along it's entire length. Yes,
the intake is higher in the intake manifold and less after the throttle
body, but less is not the same as no vacuum. And again, if there
were no vacuum, then that line couldn't perform the function that is
claimed in the fuel pressure regulator reference that YOU provided.

Bring me 15-20 inches of vacuum then we will talk.

[glenwyatt]

Funny to listen to the bickering. You will not find any vacuum ahead of the throttle blade. Or, at least the vacuum gauge I have shows nothing. That said, there is obviously some vacuum but it's not going to be anywhere close to manifold vacuum and unless you're using a gauge which is not your standard automotive vacuum gauge you won't find the needle moving.

[jfoj]

Originally Posted by trader4

I have said since the first post that the vacuum is going to be less
ahead of the throttle body and that less vacuum does not equal no vacuum.
That was my whole point. The gauge argument is
like saying because an ammeter that has a range of 1 -100 amps
doesn't register 100ma, that no current exists and then disputing
the sound, basic science that shows it does exist. And it's also silly,
because even the technical description that Jfoj himself posted,
clearly requires a vacuum to be present for that line that is routed from
the fuel pressure regulator to the intake ducting to work for the
purpose that is stated. I honestly don't know what his problem is.
From my first post, I essentially supported what he was saying, just
that he's wrong that there is *no* vacuum in the ducting ahead of
the throttle body, which was also Upallnight's point. And you agree
on the vacuum point too.

glenwyatt is on the ONLY one who understands what is going on here.

Some of the E53 crowd (I probably could use a more descriptive adjective) here just constantly wants to argue and toss out YouTube videos, Wiki links and high school physics as a smoke screen that they can hide behind and just continue to argue what they believe when they cannot even understand or think outside of the box. This is the PROBLEM with so many forums and the Internet. Would love to see how political "discussions" would go with the same crew.

It seems that everything is taken so literally. Unless I write like a Lawyer with If, And, Buts, Shall and Will along with full T's & C's not sure I would ever get the point across and you would be arguing about the humidity.

In simple terms this same crew cannot and will not believe even what the BMW documentation states, albeit a bit unclear. The PDF I posted covers both the M52 and M54, unfortunately the person/people that wrote the document did not CLEARLY divide the M52 vs M54, but I believe a 6th grader would and could understand the reference of the FPR connected to the "cyclonic oil separator" or CCV was meant for the M52. If anyone would pop their hood on their M54 and trace the hose (NOTE IT IS NOT A VACUUM HOSE, IT IS A RUBBER HOSE) from the FPR you will CLEARLY see it is NOT connected to the "cyclonic oil separator" or CCV. Enough said and any REASONABLE person would see and understand this.

So I guess the BMW document is WRONG where it states "The attached fuel pressure regulator no longer controls fuel pressure influenced by vacuum supply". Have you ever lived overseas or worked internationally? I have and I have seen translation errors and confusion all the time when converting documents and when the documents are unclear to begin with errors are magnified.

Vacuum, well in THEORY (which will be argued and debated until we find the end of the Internet on the Xoutpost E53 forum) with exception of deep space which none of use has visited that I am aware of, however (I do suspect that Janet From Another Planet may frequent this forum) will only be present in a sealed or severely restricted chamber, pipe or hose. Otherwise there will be no "vacuum" just "airflow". Case in point if a vacuum gauge is connected to the sucking jet pump fresh air input, you will likely measure a vacuum because the "vacuum gauge" seals off or closes the hose or pipe, BUT if you put a "T" inline to the "F" connector where the FPR "hose" is connected and connect the vacuum gauge to the "T" you will note likely measure any appreciable vacuum. Maybe if you use a VERY sensitive and precise gauge or transducer there may be mouse nuts of a measurement.

What we a dealing with or discussion is the fact that you WILL NEVER see ANY appreciable vacuum at the intake boot connection that will vary, change or influence the FPR at all. There may be a VERY SLIGHT change due to barometric pressure with significant changes in altitude, but this would likely be so minuscule it would be very hard to measure.

So between the front bumper of the car and the throttle plate there is little to no restriction. The air filter is the only real restrictive part the surface area of the filter and maybe the MAF as there is some obstruction and air path modifiers inside the MAF is such that it virtually non existent, otherwise most owners would be tossing the air filter box and MAF in the trash and gaining 10 HP. It has been discussed and pretty well proven for many BMW models that the stock air filter box, MAF and intake tubing is about as good as it gets, most modifications hurt the engine performance.

So my point is you have a LARGE cavern, in front of the throttle valve, with very little restriction to airflow that is for the most part always at atmospheric pressure.

To put is simply there is not any significant "vacuum" at the connection in the intake boot. There is not 5-20 inches of "vacuum" to control the fuel pressure on the M54 engine, BMW states the M54 engine does not have fuel pressure "influenced" by vacuum supply.

Quoted directly from the BMW document "The ECM now determines the fuel quantity compensation for the manifold vacuum changes. This is based on the throttle position sensor, air mass meter, load, etc. for precise compensation.

Kind of funny how even the BMW document refers to the DME as a ECM in this case. Probably a translation problem or a third party writing the document in English.

So I will let the arguments continue, I am sure I have provided AMPLE things for some members here to pick and beat to death. It is quit sad these same members do not go and test things for themselves and CRITICALLY read and review the BMW documentation as well as just inspect and think about how the M54 FPR system is configured.

But as they say, often you cannot teach and old dog, new tricks!

[1iwilly]

problem fix with new fuel pump install thanks to all the reply
thread can be close

[jfoj]

Thanks for updating the thread, too bad the thread had to take the direction it did.

BMW uses different pumps across some of the chassis, some are Siemens/VDO, others are Pierburg. From the E46 chassis, the pumps are Siemens/VDO except for maybe the M3, and based on history, EVERY E46 should have a replacement fuel pump by now if you want a reliable vehicle.

Pretty much hold true for the E53 even if it may run a Pierburg pump, which it may as the E53 is a cousin of the E39.

For the pump price and the ease of replacement, it makes no sense to brag about how old or how many miles the fuel pump may have. I prefer to proactively replace electric fuel pumps by the cars 8-10th birthday because I do not like walking when I should be driving.

I think everyone will see that the E53 pumps will soon start failing in large numbers if they have not already started. The no starts tend to begin in the Winter months with the cold temps and after the vehicle has sat over night for a good cold soak. But before the pumps cause no starts, they get soft/weak and cause driveability problems and will cause the sucking jet/siphon pump to not work properly and the vehicle will also "run out of fuel" with the tank displaying 1/4 full.

I am sure everyone will have their own opinion and make up their own mind, but I highly recommend replacing the fuel pump as a preventative measure.