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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 05-03-2015, 06:50 AM
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gmak2012 gmak2012 is offline
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Exclamation Running Rich Saga: Fuel pressure too high - need some advice

I have a possible resolution See the post from May 29, 2015. It's a high possibility that it's the FPR. I will wait and see how the trims are affected by other work I've done and then decide if I will replace or not. The spark plugs I checked are white / grey on the ends (they're platinum ones) with no black soot - so the DME is doing it's job. I did find some oil on the threads of #1 spark plug, so a valve cover gasket job is likely in my future


UPDATE #2 June 20, 2015: The new FPR has resulted in fuel pressure at the rail to be 48 PSI. This is a bit low - but it may be due to a leaky VCP.

FINAL UPDATE Jan 1, 2016: I believe that INPA reports invalid results. Using TORQUE, my fuel trims are just fine - practically perfect.


1. Fuel pressure for a cold car, engine off is about 35 - 40 psi
2. Fuel pressure at idle is 65 psi
3. Fuel pressure when revving engine up to 2000 rpm stays at 65 psi
4. Fuel pressure when take vacuum off of Fuel Pressure Regulator (FPR) goes up to 75 psi

The FPR is working - but maybe not fully (??). i.e. Diaphragm /spring inside don't relax enough to let fuel pressure fall. Could a faulty fuel pump cause the pressure to be too high? Can it be adjusted?

I thought that I would replace the FPR with a $34 Bosch one since the one on there is true-blue BMW (and only 3 years old on my car - who knows how long it sat in a parts warehouse before that - or if it isn't some cheap knock-off (it's been a while and I don't remember who I ordered from).

Is there any other advice? The car runs just fine apart from the high fuel pressure (with silightly lower mpg that I would otherwise get) - but I'm worried that at some point the DME won't be able to compensate and I will be looking at a CE - not to mention the slow but steady damage to the cats. I'm also worried that perhaps it will reach a point where there is difficulty starting as things progress. And yet, it's been like this for at least 3 years that I know of....

Again, any advice would be greatly appreciated because I don't want to start throwing parts at the fuel pump if that is not the way to go. I'm hoping for a simple solution to this (fingers crossed) and maybe a new FPR will do the trick.

Cheers.

Last edited by gmak2012; 01-01-2016 at 07:21 AM.
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  #2  
Old 05-03-2015, 07:17 AM
pshovest pshovest is offline
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Are you sure gage is accurate?
No CEL, what prompted you to check fuel pressure?
Cat damage is not likely. If pressure is actually high, DME will compensate by reducing fuel trims. You can see fuel trims with INPA and many inexpensive OBD2 code readers like Actron 9145.
Bad FPR or blocked return line downstream of FPR.
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Old 05-03-2015, 07:27 AM
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I disagree with you that your fuel pressure regulator is working. I don't know what the exact fuel pressure spec is for the fuel pump but I'm sure 75 psi is fine.

It is the job of the FPR in our cars to regulate FP so it is 3.5 Bar or about 50 PSI at idle, not 65 psi.

I totally agree with pshovest's above. After you make sure that your Fuel Pressure gauge is correct and the fuel return line is clear, replace your FPR. IMHO it is worth buying an OE FPR (not an OEM one).
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  #4  
Old 05-03-2015, 08:05 AM
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gmak2012 gmak2012 is offline
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Thanks guys.

@pshovest: I've had negative trims for a while. FPR was the last element to investigate, outside of looking for leaks or O2 sensors not in correctly on the exhaust side.
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  #5  
Old 05-03-2015, 08:13 AM
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540iman 540iman is offline
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Quote:
Originally Posted by pshovest View Post
Are you sure gage is accurate?
No CEL, what prompted you to check fuel pressure?
Cat damage is not likely. If pressure is actually high, DME will compensate by reducing fuel trims. You can see fuel trims with INPA and many inexpensive OBD2 code readers like Actron 9145.
Bad FPR or blocked return line downstream of FPR.
The FPR is manufactured the way it is so that the DME, through feedback from the O2 sensors by the action of the fuel trim adjustment may be at a minimal amount to be able to hold the mixture at close to 12.5 to 1. There is, of course, a value for the FPR that becomes the manufacturing tolerance- a high and a low value to assist the O2 sensors with sending to the DME an air/fuel ratio needing fairly close to "zero" adjustment (fuel trim) ideally. BMW, knowing that the FPR is simply a diaphragm and a spring will have (or could have) quite a bit of process variability when the fuel pressure filter/regulator is made. Ideally it would keep the pressure between 45-50 PSI which will make for a very easy trim value across the rpm/load range. It sounds like your FPR was just at the high end of the manufacturing process, but within the capability of the values the DME will need to store in your trim table. I agree with the OP who said if your fuel pressure becomes more than the trim table can adjust for, YOU WILL get a SES error. You just need to have the confidence that your O2 sensors are good and that they will take-over from here. If you were having what you *thought*was a rich condition, then the O2 sensors would be the correct suspect. If they are operating correctly, their output would swing rapidly about and below .5VDC but they would "swing" between about .2V and .8 V trying to be centered at about .5VDC. If your tail pipe were to be cleaned and then rapidly turned sooty with unburned fuel QUICKLY, then I would check your pre-cat 02s.

Last edited by 540iman; 05-03-2015 at 08:18 AM.
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  #6  
Old 05-03-2015, 08:30 AM
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gmak2012 gmak2012 is offline
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Really good information in this thread. I never knew that about the FPR. I'll clean the tail pipe (it's the scuba tank with tip turned down) and see what happens. Meanwhile, I think an OE (Bosch) FPR might be a cheap test.

O2 sensors are 2 years old.

Last edited by gmak2012; 05-06-2015 at 05:25 PM.
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  #7  
Old 05-29-2015, 02:52 PM
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gmak2012 gmak2012 is offline
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Here is an update and some developments

As part of my pursuit of a knocking noise, I put a new gasket in for the SAP check valve (tin man) and tightened up the nuts there. I think that this may have reduced fuel pressure issues from some kind of exhaust leak (the knocking noise dropped in volume considerably and relocated - but that's in another thread).

I just checked the fuel rail pressure using two different pressure guages. I have something from either TIS or a BMW repair manual that states that you have to record the fuel pressure with the engine running, then shut off the engine and see where the pressure goes.

If the running engine pressure is too high and the pressure returns to normal when the engine is shut off, then the issue is supposed to be in the fuel return line - some kind of blockage.

If the running pressure is too high and the pressure remains higher than normal when the engine is turned off, then the issue is with the Fuel Pressure Regulator.

With both gauges, I registered 60 psi with engine on and 55 psi with it off. NOTE THAT THIS IS LOWER ON BOTH MEASURES THAN THE LAST TIME I DID THIS WITH JUST A SINGLE GUAGE.

My hypothesis is that there was some kind of effect from the tin man that affected fuel pressure.

In any case, it's supposed to be the FPR that is the issue. I'm going to drive the car a while and then see what happens to my fuel trims in INPA and take it from there.
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  #8  
Old 05-31-2015, 08:58 AM
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Here is what the spark plug looks like.

Notice that the tips are grey / white, but that there is oil on the threads. My interpretation is that everything is working as it should for burning fuel - i.e. if there was too much fuel, the tips would be black. If too little, then brown.

The oil tells me that the gasket around the spark plug well is getting old and worn and needs to be replaced - likely with the valve cover gasket.

Does this sound correct? Or am I misinterpreting something?

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  #9  
Old 06-19-2015, 04:01 PM
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gmak2012 gmak2012 is offline
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My new Fuel Pressure Regulator (FPR) has arrived.

I think that I will pop it in tomorrow morning and see what happens to that 60 psi. There is a lot of noise in the results though, given my brake booster cavity flood.

More to come as things develop.
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  #10  
Old 06-19-2015, 06:10 PM
edjack edjack is offline
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The only way that oil could get on the threads is if the plugs are loose, or the engine is pumping oil. The crush seal on the plug seals the threads from the outside.
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  #11  
Old 06-19-2015, 06:54 PM
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what does it mean "the engine is pumping oil"? something bad probably - but what?

i mean, wouldn't it be the VCG and tube seals?

Last edited by gmak2012; 06-19-2015 at 07:03 PM.
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  #12  
Old 06-20-2015, 06:26 AM
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Ed means (I believe) if your rings were bad (for example). Even if you have a bad valve cover gasket, the threads would only show oil as "fresh and wet" oil from removing the plug through a bath of oil. I believe ED is telling you that for oil to be "baked on" the threads as indicated by possibly burnt looking and on the bottom threads would be if very loose and/or your rings are bad. Or, oil on the very tip of the plug would indicate blow-by.

Are we now done with the fuel pressure issue? If you were too rich (beyond reasonable) and the ECU could not compensate, you would throw a code and SES would be illuminated. How is car running overall and what mileage are you getting? Describe your driving pattern honestly. Around town and stop and go, highway, mix....and are you in the habit of pressing the accelerator like a sewing machine pedal?! When my fiancée drives my car, she will ride in left lane going speed limit or less and then whenever car comes up behind her, she steps on gas pedal only to let off again and cycle repeats. If she would just get over and pace herself, she would not drag my MPG down from say 20 to 17 on same trips I take! I even use cruise control on smaller 4 lane roads to max. out my mileage!

Our cars operate in a very controlled and efficient "closed loop" where multiple sensors "tell on" each other to guarantee emissions. If running too rich, O2s will "tell on" the injectors. If ECU is unable to get your mixture right because adaptive values are maxed-out, that too will set a code. System is pretty darn smart. I doubt your pressure was ever really an issue if you did not have appropriate codes.
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  #13  
Old 06-20-2015, 08:25 AM
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I'm not done. This is a long 1,000 step journey. I have a new FPR and I'm putting it in today. If the pressure doesn't go back to standard then the last refuge (I think) is the return piping / hose and 3/2 way valve (yeah, I have one of those monstrosities).

The fuel pressure issue is because I had very high negative adaptations (both additive and mulitplicative) on the trim page in INPA. I believe, given how my spark plugs look, that the DME is doing a great job of adjusting the trim for too much fuel - so I'm not really 'running rich' except a various points in the adjustment cycle. I just want to get my trims closer to zero - especially the long term ones.

FYI, I don't have burnt on oil on the threads. It's wet and minimal. I have a VCG and tube gaskets in my near future when I do the new (result from Dr) Vanos.


I really appreciate the wealth of knowledge here and the willingness of many to share that knowledge - especially people like yourself, EdJack, CN90, and many others too numerous to remember the names. And thank to Bluebee for her endless questions and archiving of the communal knowledge here. Who knows, you all may make a proper wrenched out of me yet.

Cheers.
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  #14  
Old 06-20-2015, 08:43 AM
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Running Rich Saga: Fuel pressure too high - need some advice

Have you checked the fuel breather system? Specifically the float valve to the charcoal canister's expansion tank. The float valve can break, causing pressure to build up, high fuel consumption, power loss, surging, list goes on...
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Last edited by boostedwolfie; 06-20-2015 at 08:46 AM.
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  #15  
Old 06-20-2015, 08:51 AM
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Nowhere near doing that. I don't believe that my symptoms are that drastic as to point in that direction. I'll add it to the list on this journey to get rid of the negative trim. Thanks.

One thing for sure, is that I ALWAYS come back and post what I find - dumb or smart. Hence my post somewhere around here about the ASC light after booster cavity flooding that turned out to be a slightly loose connection at the sensor / control on the ASC throttle. There is nothing worse than a thread that trails off with no solution.

Last edited by gmak2012; 06-20-2015 at 08:52 AM.
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Old 06-20-2015, 10:38 AM
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Quote:
Originally Posted by gmak2012 View Post
Nowhere near doing that. I don't believe that my symptoms are that drastic as to point in that direction. I'll add it to the list on this journey to get rid of the negative trim. Thanks.

One thing for sure, is that I ALWAYS come back and post what I find - dumb or smart. Hence my post somewhere around here about the ASC light after booster cavity flooding that turned out to be a slightly loose connection at the sensor / control on the ASC throttle. There is nothing worse than a thread that trails off with no solution.

Very good practice, we all certainly benefit from an answers. Are you saying you've solved your problems? Sorry i didnt read through the whole thread.
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Old 06-20-2015, 02:57 PM
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The problem has changed or been resolved. I put in the new FPR and fuel pressure at the rail was 48 psi. That's a little low - may be a slightly leaky VCG (which is already on the agenda to be replaced when the VANOS gets done).

I've reset the adaptation to take the trims to 0, and we'll see where they go from there. I'm hoping for a notional value as close to zero as possible as an indication of success for 'running rich', even though the DME was successfully compensating.
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Old 06-20-2015, 03:44 PM
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Quote:
Originally Posted by pshovest View Post
Bad FPR or blocked return line downstream of FPR.

Thats all you need to know..

actually... you guys got this... your all on the ball here...
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  #19  
Old 06-21-2015, 08:23 AM
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Don't pay too much attention to the fuel pressure unless it were really wildly high or low. You will be chasing a ghost that can't harm you! Whether 48psi or 68psi, the ECU does a magnificent job of compensating. Let things like drivability and MPG be your concerns and not making life for the ECU to be *easy* in terms of adaptation values. Let it do the work it was made for!
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Old 06-21-2015, 10:26 AM
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Originally Posted by gmak2012 View Post
The problem has changed or been resolved. I put in the new FPR and fuel pressure at the rail was 48 psi. That's a little low - may be a slightly leaky VCG (which is already on the agenda to be replaced when the VANOS gets done).

I've reset the adaptation to take the trims to 0, and we'll see where they go from there. I'm hoping for a notional value as close to zero as possible as an indication of success for 'running rich', even though the DME was successfully compensating.

Trust me I understand, but if you havent been back there (behind driver rear wheel liner) yet, I'd certainly check it out. My entire engine compartment is new, the most noticeable change in overall driveability occured after i started replacing things behind that rear wheel well liner.
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  #21  
Old 07-13-2015, 03:42 PM
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Curiouser and curiouser - now positive adaptation.

I've changed the VANOS, put in new lifters, changed the VCG - all part of ongoing preventative maintenance unrelated to this issue.

Then, I uninstalled my Shark Injector tune for the 1998 528i M52 engine. No change in idle, no change in Adaptation.

I put some gasket sealant (Permatex Black) on the tin man and put it back into place. What a difference in the SAP sound when it started up. I guess that 'pinky' left hand stud holding it to the manifold was not letting me get a good seal.
I took out the ICV and cleaned it (even though it didn't seem to need it). I re-installed the Shark Injector tune.

My idle is essentially unchanged (see INPA print screen below). My adaptations have gone positive suggesting vacuum leaks (see INPA screen below). At least those are more common. Obviously the first place is the ICV - i.e. did I get it back in the manifold properly. The second place I'll look is the VCG. After that, it's all the hoses and tubes - even though I replaced them with silicone ones 2 - 3 years ago.

Here are some INPA screen prints.
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  #22  
Old 07-14-2015, 05:44 AM
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gmak2012 gmak2012 is offline
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Yeah. Pretty sure it's the ICV not seated properly. Squirted some throttle cleaner down in that area (through the space on top of the intake manifold). Watched the revs drop to almost stall.. I'm going to try to get a moving or yoga strap around the bottom of the ICV to get leverage to pull the grommet and top part of the "T" up into the intake manifold to get it seated properly. Then, it will probably be back to negative trim.

I can't wait for the RV tire valve extender to get here so I can get a proper fuel pressure measurement.

As others have suggested - after this I'll probably just let sleeping dogs lie. Although, I really really would like to know the underlying cause and how to fix the higher idle. C'est la vie.
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Old 07-15-2015, 04:37 PM
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gmak2012 gmak2012 is offline
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It was the small vacuum hose that slides up between the intake manifold temp sensor and the larger black vacuum hose just in front of the ICV. It came out when I was re-installing the ICV. The car is now back into negative trim territory, as expected.

I seem to have a fluctuating idle, though. It varies from around 735-ish to 775-ish. More stuff to figure out. Good times.
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Old 07-21-2015, 02:35 PM
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One more step complete on this journey - almost there

I got some hose pinch pliers and pinched the fuel return hose located off of the top of the fuel rail. THERE WAS NO CHANGE IN IDLE WHATSOEVER. Pinching the other hose stopped the car, confirming my first choice as the fuel return line.

Here is the set up I have in my car with the 3/2 way valve and the Fuel Pressure Regulator (FPR) under the driver's seat. As a reminder, it's a 1998 528i with a production date of 09.1997. I have replaced the FPR already and got some decent results in terms of fuel pressure. But it looks like my high idle is possibly being caused by constriction or blockage in the fuel return line.


I pinched #7 here. The one on the left. Should I also be pinching #5 in this diagram?

My question is: Do I now have my answer? By this I mean, given that I pinched the hose up by the fuel rail, does this mean that there is a blockage in the return line somewhere - or can it still mean that the 3/2 way valve may be insane itself? Would it help if I pinched the return line past the 3/2-way valve in terms of diagnosis - or can I safely conclude that I need to either blow out / clear the return line, or replace it? i.e. HOW DO I PROCEED FROM HERE?


Thanks again for anyone who takes the time to read this and has some insight.

p.s. In this document it says (emphasis added) that after the first minute, the 3/2-way valve shuts off the return from the fuel rail. Now I'm really confused since my pinch test seems to be next to useless in terms of new information.
Quote:
M52 USA and M73 (see drawing 5.2/ 5.3)
The fuel is routed from the electric fuel supply pump via the fuel feed line and the fuel filter to the fuel rail.
RA Fuel supply system E38 / E39 (spark-ignition engines) BMW AG - TIS 08.05.2009 23:55 Issue status (01/2005) Valid only until next CD is issued Copyright Page - 1 -
page1image66328 page1image66488 page1image66648
The fuel returns to the fuel tank via the 3/2-way valve (see view A), the pressure regulator and the fuel return line.
This engine fuel circuit with return from the fuel rail is then switched for engine starting and a defined time < 1 minute.
After this phase, the 3/2-way valve switches and interrupts the fuel return from the fuel rail. At the same time, the line branch directly at the fuel filter is activated by the 3/2-way valve to the pressure regulator (see view B).
The fuel rail is now return-free.

Last edited by gmak2012; 07-21-2015 at 03:01 PM.
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  #25  
Old 10-02-2015, 09:06 AM
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gmak2012 gmak2012 is offline
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Just a little visit to do an update. Using Torque, my fuel trims are excellent. But I still have the higher RPMs on idle. Further digging has shown that my Throttle body sensor has a resistance range that is not in keeping with spec. ie it is indicating that the throttle is open more than it is. Changing the sensor does nothing, as both sensors provide about the same result. It seems to be a function of where the metal post on top of the throttle is positioned compared to the valves actual position in the throttle.

If I ever resolve this, I'll come back and post.\


But beware: It looks like there are versions of INPA where the MS41.1 DME data that is feeding the charts and graphs (including how the raw data is translated into information) may be wrong.
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