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So the fuel pressure regulator in M52, connected to CCV is operated with crankcase vacuum?
I have an M54 so I'm not really familiar with your engine. I have though seen the pictures and diagrams of the air hose off the CCV running to the fuel pressure regulator.

When I first saw those pictures a couple of years ago, I was baffled at the design intent. I finally realized that "operated with crankcase vacuum" is technically accurate. But assuming the CCV is working properly it is really so close to atmospheric pressure that it makes no practical difference. The CCV regulates crankcase vacuum to less than 15 millibar, or EDIT 1.5% (not 0.15% in original post) different from atmospheric pressure.

I think the purpose of taking a reference pressure this way is to provide clean, filtered source of atmospheric pressure to the fuel pressure regulator without any chance of engine bay dirt, grit and grime fouling the sensitive parts of the small fuel pressure regulator. By comparision, the CCV is about 3 inches in diameter & much less sensitive to dirt. An awkward, klugey way to achieve the result in my opinion.

For the M54, BMW changed the design to take atmospheric reference pressure from the F fitting in the boot between the MAF and inlet manifold. That supply is kept clean by the engine air cleaner.
 

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So the fuel pressure regulator in M52, connected to CCV is operated with crankcase vacuum?
I typed /m52 ccv F3 in the bestlinks and it came up with this thread which covers that issue in exquisite detail:
- Sorely needed clarification on how the M54 CCV vacuum port works on the M52 CCV valve connection to the fuel pressure regulator connection (1)



I think the purpose of taking a reference pressure this way is to provide clean, filtered source of atmospheric pressure to the fuel pressure regulator
So that all benefit, I appended this nice & interestingly logical information to that thread discussing, in detail, how the system seems to work.
- WHERE does the CCV vacuum source port go for the E39 CCV valves that are not plugged?

EDIT:
I tried to test the CCV system by checking manifold vacuum, as shown here - but I think I failed to conclude much of anything:
- How to test the crankcase ventilation pressure regulating valve system (1)
 

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I think you mean crankcase rather than manifold vacuum?
Hmmm... good point. Which vacuum 'did' I test (crankcase? or manifold?) when I ran the inconclusive vacuum test?

Looking back here, I see I wrote:

So, it appears you are correct in that the dipstick guide tube should be crankcase vacuum. Right?


Why did you fail to conclude much of anything.
Well, here are my data points:

  1. Original CCV (2002 model year)
  2. Warm dry weather (Silicon Valley)
  3. 8 inches of "crankcase" vacuum
  4. Vent pipe blow test showed no resistance
  5. No misfires
  6. Dipstick 'was' clogged solid - but it has been cleaned out
  7. No smoke whatsoever on exhaust (California smog tests are nearly perfect)
Given that conflicting information, I'm not sure WHAT the state of the CCV is in.



 

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I have an M54 so I'm not really familiar with your engine. I have though seen the pictures and diagrams of the air hose off the CCV running to the fuel pressure regulator.

When I first saw those pictures a couple of years ago, I was baffled at the design intent. I finally realized that "operated with crankcase vacuum" is technically accurate. But assuming the CCV is working properly it is really so close to atmospheric pressure that it makes no practical difference. The CCV regulates crankcase vacuum to less than 15 millibar, or EDIT 1.5% (not 0.15% in original post) different from atmospheric pressure.

I think the purpose of taking a reference pressure this way is to provide clean, filtered source of atmospheric pressure to the fuel pressure regulator without any chance of engine bay dirt, grit and grime fouling the sensitive parts of the small fuel pressure regulator. By comparision, the CCV is about 3 inches in diameter & much less sensitive to dirt. An awkward, klugey way to achieve the result in my opinion.

For the M54, BMW changed the design to take atmospheric reference pressure from the F fitting in the boot between the MAF and inlet manifold. That supply is kept clean by the engine air cleaner.
I think some of the posts are incorrect. The vac hose effect is to reduce rail pressure at idle, by increasing bypass fuel flow. The cases where hose is tied to cvv may have additional effect to increase rail pressure at high rpm.
 

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... stuff deleted ...
Well, here are my data points:

  1. Original CCV (2002 model year)
  2. Warm dry weather (Silicon Valley)
  3. 8 inches of "crankcase" vacuum
  4. Vent pipe blow test showed no resistance
  5. No misfires
  6. Dipstick 'was' clogged solid - but it has been cleaned out
  7. No smoke whatsoever on exhaust (California smog tests are nearly perfect)
Given that conflicting information, I'm not sure WHAT the state of the CCV is in.

... stuff deleted ...
Two years ago, my car failed vacuum at 9 inches but had no symptoms at all: engine performance & idle qualtity were normal, no DTCs were present and no smoke from the tailpipe. A couple of months later the CCV system failed entirely. The engine then refused to idle, generated a raft of DTCs and lit up the CEL. Even after failure, I had no smoke. However, while replacing the entire CCV system I discovered a hole in the drain hose to the sump which created a large vacuum leak. The CCV valve body may have been functioning well enough to avoid driveability symptoms if the drain hose hadn't failed.

The 8 inch vacuum by your engine is a failure vs the specs of 4 - 6 inches. I conclude your CCV is failing but not so badly as to generate driveability symptoms. FWIW, if this were my car I'd continue to drive it but check vacuum regularly and have new CCV parts on hand. My logic being that although out of spec, the 8 inches of vacuum is still so weak that it is very unlikely to generate any other problems. And I don't know what I'd consider too much vacuum to tolerate; probably 12 inches (2 times upper spec) but that is an absolute double X triple WAG - not a SWAG since there is no science behind it. Or maybe I'd just wait for a nice day, replace the darn thing and be done with it.

I've never been able to understand the physics behind the blow for bubbles test. And I never got bubbling: not with 9 inches vacuum, not after my CCV failed entirely (but then it wouldn't with a hole in the drain hose) and not after CCV replacement with vacuum in spec.

Consider that with the vent hose disconnected from the valve cover and blowing into it, the chamber in the CCV is at atmospheric pressure or slightly above; certainly no vacuum. Therefore the CCV's diaphram and orifice will be wide open, ready to draw vacuum on the vent hose (and thus crankcase, if connected) as soon as the engine is started and inlet manifold vacuum is present. The air being blown into the vent hose will take the easy route to the inlet manifold rather than the path down into the sump to make bubbles. It seems to me that the only way to get bubbling would be for the diaphram to be failed closed or the distribution piece on the manifold to be clogged. In this case one would have +ve pressure with the engine running - a definite CCV failure. Yet a pass for a good CCV is supposed to be a little resistance and bubbling when blowing into the vent hose.
 

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I think some of the posts are incorrect. The vac hose effect is to reduce rail pressure at idle, by increasing bypass fuel flow. The cases where hose is tied to cvv may have additional effect to increase rail pressure at high rpm.
You're correct that my explanation is wrong or at very least incomplete. I checked TIS and the M52 engine does adjust fuel pressure depending inlet manifold vacuum. The M54 engine does not; it uses constant fuel pressure.

However, based on pictures and diagrams I've seen, the connection point on the CCV should be at crankcase vacuum, which is a constant 10 to 15 millibar vacuum. Essentially atmospheric; nothing like the 700 to 900 millibar inlet manifold vacuum seen during idle or over-run. So I can't explain the connection and response by the fuel pressure regulator.

I regret posting the mis-information on this question. I hope that someone else can provide an accurate explanation.
 

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Two years ago, my car failed vacuum at 9 inches but had no symptoms at all
Interesting. Where did you check the vacuum from? I placed my clear hose over the dipstick.

I have been meaning to doublecheck mine again just to make sure I didn't do it incorrectly so if there are other places to doublecheck the vacuum, that would be useful as a check of my procedure.

A couple of months later ... the engine then refused to idle, generated a raft of DTCs and lit up the CEL.
I had that exact problem just a few months ago:
- Does the ORDER of pcodes listed in an OBDII scanner actually matter?

A smoke test implicated the lower vent hose to the CCV, which, like yours, was holed (in fact, it was nearly broken in half!).


Even after failure, I had no smoke.
Even with that holed CCV hose, I also experienced no smoke. But there were tons of lean-misfire codes!

I conclude your CCV is failing but not so badly as to generate driveability symptoms.
I don't disagree. Plus, the CCV is definitely original, so it's a decade old at this point in time.

I'd continue to drive it but check vacuum regularly and have new CCV parts on hand.
I understand that logic. That's what I did with my cooling system. The CCV, even for you guys, is a pain. So just imagine how time consuming it will be for me!

I've never been able to understand the physics behind the blow for bubbles test.
Me neither. I don't personally think it tests anything. I said so in the aforementioned CCV test thread but I'll append your deduction also so as to add weight to the premise.
 

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My comments in red font

Interesting. Where did you check the vacuum from? I placed my clear hose over the dipstick.

I checked via the dipstick tube.

I have been meaning to doublecheck mine again just to make sure I didn't do it incorrectly so if there are other places to doublecheck the vacuum, that would be useful as a check of my procedure.

The only practical option that comes to mind is the oil filler. Either drill out a cap and fit a hose barb or a fabricate a flat plate with gasket surface and hose barb.

I had that exact problem just a few months ago:

I wound up a boatload of lean related codes too.
I think that what happened is that the CCV was failing vacuum but without any driveability problems. But the hose was still intact or only very slightly holed. When the hose failed for good a few months later, the vacuum leak caused all the driveability symptoms and DTCs. I wish that I had checked crankcase vacuum then; I'm almost certain that it would have been zero at that point. I suspect I could have gone a several more months (at least until warmer weather) without any problems if the drain hose had not failed.

- Does the ORDER of pcodes listed in an OBDII scanner actually matter?

A smoke test implicated the lower vent hose to the CCV, which, like yours, was holed (in fact, it was nearly broken in half!).
... image deleted ...

Even with that holed CCV hose, I also experienced no smoke. But there were tons of lean-misfire codes!

I don't disagree. Plus, the CCV is definitely original, so it's a decade old at this point in time.

Old doesn't necessarily mean defective. But with plastic ...

I understand that logic. That's what I did with my cooling system. The CCV, even for you guys, is a pain. So just imagine how time consuming it will be for me!

The CCV renewal is certainly a few hours but straightforward, not so difficult except for the infamous S tube to the CCV valve. Most people report spending a LOT of time on this connection. I did, IIRC over an hour before the light bulb came on. There is a solution,
http://www.bimmerfest.com/forums/showpost.php?p=5912837&postcount=77
see post 77 in Fudman's DIY.

Me neither. I don't personally think it tests anything. I said so in the aforementioned CCV test thread but I'll append your deduction also so as to add weight to the premise.
 

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Steve,

It looks like both pictures that you uploaded are the same.

I'm still a little confused as to whether you agree with me and RDL on how the system functions, or if you are still taking an opposing view. I'm not trying to be sarcastic in any way, I'm just not sure if we are on the same page yet.

Thanks,

Gary
Sorry for the late reply - I just looked at this thread again.

Indeed I posted the same photo twice. I've posted the second photo below. It shows a section through the M54 oil separator part of the CCV.

I doubt this adds anything to the current discussion, but I wanted to post it for completeness.

 

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...The M54 engine does not; it uses constant fuel pressure...
On the M54 the FPR is on the fuel filter. It's connected to the "F" connector on the intake boot.

I don't understand why a FPR would need an atmospheric reference.
 

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On the M54 the FPR is on the fuel filter. It's connected to the "F" connector on the intake boot.

I don't understand why a FPR would need an atmospheric reference.
Recall the discussion of CCV operation earlier in this thread. One side of the diaphragm is exposed to crankcase pressure (or vacuum) and the "other side" to atmospheric pressure. The net force on the diaphragm working against the spring results in crankcase being maintained at 10-15 millibar (0.145 - 0.2175 psi) less than the pressure on the "other side" of the diaphragm. Since the pressure turns out to be less than atmospheric we call it vacuum.

Now imagine that the "other side" of the diaphragm is a sealed chamber with some pressure, let's say 2 psi higher than atmospheric pressure. The CCV would then maintain a crankcase pressure 10-15 millibar lower than the sealed chamber. Crankcase would be 1.9855 - 1.7825 psi pressure (not vacuum.) Alternatively, if the sealed chamber was at 2 psi vacuum, crankcase pressure would be 2.145 - 2.2175 psi vacuum (not pressure.)

By rearranging the relative positions of the spring, diaphragm and orifice plus providing a supply of high pressure liquid or gas, a regulator can be made to maintain an output pressure higher than the reference pressure. Presto, a fuel pressure regulator or welding regulator.

The point is that any pressure regulator operates to maintain a difference from a reference pressure; it doesn't "pick it out of thin air" so to speak. Since fuel pressure is specified as X psi higher than atmospheric, the regulator needs atmospheric pressure on one side of its mechanism.

As a matter of interest, not all pressure regulators use diaphragms; a piston concept is possble, as are other designs. But they all have a mechanism that compares pressures. I don't know which design is used in the fuel pressure regulator. Has anyone taken one apart?
 

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I never thought of it as a reference to atmospheric pressure. I've assumed that it was necessary too let the volume behind the diaphragm vary without restriction.

As I recall, in one type of FPR the return flow is blocked under low vacuum, such as acceleration. Another type of FPR actually increases return flow under high vacuum situations like idling. I suppose one could design a FPR to do both, but I've assumed that the FPR on the e39s are the second type that lower fuel rail pressure during high vacuum.

If I understand what you've written, you think that the FPRs on the e39s don't really use a vacuum source to move the diaphragm, only to vent area behind the diaphragm. Certainly the M54 FPR will not see a strong vacuum since it's connected upstream of the throttle. Assuming that the CCV is operating at crankcase vacuum, it would be insignificant for the M52, too.
 

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... stuff deleted ...

As I recall, in one type of FPR the return flow is blocked under low vacuum, such as acceleration. Another type of FPR actually increases return flow under high vacuum situations like idling. I suppose one could design a FPR to do both, but I've assumed that the FPR on the e39s are the second type that lower fuel rail pressure during high vacuum.

If I understand what you've written, you think that the FPRs on the e39s don't really use a vacuum source to move the diaphragm, only to vent area behind the diaphragm. Certainly the M54 FPR will not see a strong vacuum since it's connected upstream of the throttle. Assuming that the CCV is operating at crankcase vacuum, it would be insignificant for the M52, too.
A simple FPR will do both automatically, it wouldn't need two different types or a special, complex design. In both the cases you describe injector pressure changes in the same direction as the change in reference (manifold) pressure. This is normal response for a pressure regulator. You can work through the steps by considering vacuum to be -ve pressure and that blocking return increases injector pressure, increasing return flow reduces injector pressure.

I should clarify that vacuum doesn't move the diaphragm and the hose isn't simply a vent. Rather the balance of force from reference pressure on one side, force from fuel pressure on the other side, plus spring force determines the output pressure. The purpose of the air hose to FPR is to provide the reference pressure that the engine designer planned.

TIS describes that the M52 does change fuel pressure under different engine load conditions (high load / acceleration = low manifold vacuum, low load / idle = high vacuum) and apparently uses varying vacuum to the FPR to do so. However as I mentioned in the earlier post, I just can't work out how the tap off the CCV provides that changing vacuum to the FPR. :(

TIS does not say anything about the M54 varying fuel pressure with load.
 

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I can't find the description of the M52 FPR operation in the online version of the TIS. Are you looking at another version? However, that is exactly how I assumed the M52 FPR worked. And that is why I assumed that the vacuum port on the CCV was operating at manifold pressure.
 

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I can't find the description of the M52 FPR operation in the online version of the TIS. Are you looking at another version? However, that is exactly how I assumed the M52 FPR worked. And that is why I assumed that the vacuum port on the CCV was operating at manifold pressure.
Here is a portion of the TIS procedure for checking fuel pressure on an M52. You will see it specifies a change of 0.4 to 0.7 bar (6 to 10.5 psi) between idle and full load condition.

The corresponding page for an M54 notes a single test value. No mention of differing values between engine load conditions.

This is the 12/2007 TIS data.
 

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I found this about the M52 in the online version of TIS:

Description of operation: fuel pressure regulator
Depending on requirements, the fuel pressure regulator regulates a low or high fuel pressure. This requirement is set with the help of the pressure regulator.
Depending on the engine's operating state, less or more fuel is needed:
- at idle speed, less fuel
- at full load, considerably more fuel.
The injection rate is precision-adjusted by means of the injection time; the injection time is controlled by the DME.
The partial vacuum in the intake manifold serves as engine load information for pressure regulation. The diaphragm of the pressure regulator is actuated with this partial vacuum.
A partial vacuum builds up in the intake manifold during idling operation or in overrun mode. Depending on the partial vacuum value, the fuel pressure decreases starting out from the nominal value. The nominal value is stamped in the fuel pressure regulator housing.
At full load, the partial vacuum in the intake manifold is approximately equal to zero. The fuel pressure regulator regulates the fuel pressure to the nominal value stamped in the housing.
And this for the M54:

Description of operation:
The control function of the fuel pressure regulator must be guaranteed under all operating conditions. The fuel pump must always be able to generate a higher fuel pressure than the pressure regulated by the pressure regulator.
The injection rate is adjusted by means of the injection time; the injection time is controlled by the DME.
Description of operation: fuel return line
When the engine is at a standstill and the ignition key is in position 0, the fuel return line after the pressure regulator is at zero pressure.
Description of operation: pressure retaining function
The pressure regulator closes when the engine is at a standstill and the ignition key is in position 0. The fuel pressure in the delivery line is retained over an extended period. A non-return valve closes in the fuel pump. These measures help to retain the fuel pressure in the fuel system. Extended starting times are thus avoided.
 

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I think we have two good threads for testing the CCV:
> E39 (1997 - 2003) > Cute little trick to diagnose blocked CCV system...
> E39 (1997 - 2003) > How to test the BMW E39 pressure-controlled crankcase ventilation system (CCV)?

So, I'm not sure which should be the canonical thread to cross-reference this information posted today (in order for others to find it more easily in the future, long after we're gone).

Just checked crankcase pressure from both the dip stick and the oil fill. Both readings about -6"wc with a warm engine.


...my CCV was bad. I just replaced and had a big rip in the diaphragm. Tested the new one with a manometer and has reading moving around from 3 to 6" WC.... I highly recommend the use of a manometer to test.
 

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Hi,
I was doing the 2 tests on M52 engine, balloon test on dipstick tube and bag over oil filler hole.
1. on dipstick the balloon got only slightly sucked, very light vacuum.
2. on oil filler hole the same, very light suction.
Both indicate properly working CCV? But theres one thing I noticed that I never would expect, when I removed the oil filler cap idle went up and car actually sounded really strong.
I have to say the car does feel kinda lazy, it idles smooth, but Im told bit low (~500rpm). Does this indicate not a bad ccv but more like bad MAF or vacuum leak?
I'm asking because on another e39 we had the idle went really rough when removing the oil filler cap.
 

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I just came across this interesting little trick for diagnosing blocked CCV in the Volvo forum:

With the oil cap sealed, engine on, stick a balloon over the dipstick tube and see if it inflates. If it inflates you need to service the PCV system.

...Lee


I think he meant with the dipstick removed, so the balloon goes over the dipstick housing.

No balloon, no problem, get an old dish washing glove, cut a "finger" off and tie it with rubber band.

http://www.matthewsvolvosite.com/forums/viewtopic.php?f=1&t=28322
Just found this tip in a Google search, thank you for posting it CN90. What if the CCV unit is plugged but the diaphram is not torn, would this still inflate the balloon? Could you use B12 Chemtool or Seafoam in the vacuum lines to help clean the valve rather then replace it should it be a low mileage engine, or was already replaced less then 50,000 miles ago?
 
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