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Thread: Diagnosing WUR correctly?

  1. #51
    Join Date
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    1981 E21 318i
    Hi ..

    I found this cross sectional drawing of the fuel pressure regulator that might be of some help.

    From the look of it .. the piston in the regulator is downstream from the internals of the fuel distributor. So the missing O ring or it's remains would tend to be pushed out of the fuel return.

    I can think of two things to try .. Firstly to check the passage from where the fuel return line bolts on. Use a bit of copper wire to probe the passageway for obstructions (so you don't run the risk of scratching the bore where the regulator piston works).
    Also, because of the other problems you have been having, it's probably a good idea to do the same with the passage where the return line for the WUR bolts on.

    Then I'd be tempted to refit the regulator without the piston and run the fuel return line into a can and see if anything is flushed through with the fuel pump running.

    Cheers

    Ohh .. another thought ... you have had the WUR return line and the cold start injector line attached the right way round on the FD ?
    Attached Images Attached Images
    hmm .. Wonder what happens if I do this ...

  2. #52
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    Awesome, Graham! I was trying to find a cut-away view last night, to no avail.
    Tbd

  3. #53
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    IMG_20170429_211451642.jpgThanks so much, the cut-away view helps a lot! I don't think that the O-ring could have gotten past the piston of the regulator in order to get into the return line, but I blew air from the return line anyway and it was clear. It does look like the o-ring could have gotten into the line to the cold start injector, so I disconnected that line and blew all the gas into a jar, no visible chunks came out. I took out the fuel distributor so that I could check it out in more detail, and the o-ring is not in there in any place that is visible. I can only guess that that o-ring has been gone for as long as I have owned the car, which seems amazing that it didn't cause any issues. The picture is of the entire pressure regulating assembly as it came out of the fuel distributor.

    I ordered o-rings from McMaster Carr, and also ordered other sizes to rebuild the fuel distributor. Those will probably be here before I have a chance to work on the car again (later this week), but I did get the fuel distributor apart and it looked pretty good inside. The plunger moved freely, and no rust or junk inside, just some thin deposit on the stainless diaphragm, and some of the o-rings look like their cross-section may no longer be entirely round. The deposit on the diaphragm did not look like varnish, it was almost like a calcium deposit. I got most of it off with a dry paper towel, the tougher bits came off with the smallest amount of silver polish. The only other thing that may be an issue is that the diaphragm has very slight dimpling where the four pointy ports are (on the spring side). Like an overpressure on the control side pushed the diaphragm against those ports. But it is a very slight depression, barely visible.

    As far as mixing up the WUR lines at the fuel distributor, I don't think that is even possible because one of the lines connects in the top/middle with an in-line fitting, and the other connects on the side with a banjo fitting.

    Hopefully I will have some success to report before this weekend. Thanks again, everyone!

  4. #54
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    If your pressure regulator o-ring is missing and your system pressure (and control pressure) are still that high, there MUST be an obstruction on the return circuit somewhere, either internal to the fuel distributor, or on a return line.

    '81 320i turbo | t25, 931 CIS, 240hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  5. #55
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    The pressure did go back down when I tested it later, but before I opened up the pressure regulator. I suppose one possibility is that the o-ring got loose, the pressure regulator tip pulled back far enough to allow the o-ring (or its remains) into the return line, they were still in the return line when I measured 100+ psi but had worked their way through to the tank (via residual pressure) before I tested again.

  6. #56
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    OK, the o-rings arrived, I replaced all of the old o-rings in the pressure regulator and fuel distributor with new high-durometer Viton o-rings, and re-assembled everything.

    I tested the pressures, and got 35 psi cold control pressure (60 degree ambient) and 65 psi system pressure. However, I had to test very quickly because I could hear the injectors singing. I pulled the plugs, and there was a lot of gas in the cylinders. I cleared out the gas by turning the engine by hand and running compressed air into the spark plug hole (leaving room for it to also come back out of the spark plug hole). Then tried to start it. It did run, chugging and not really getting any revs, but I could still hear the injectors over the sound of the engine because - of course - they were still flowing way too much fuel.

    Disappointing that the car still isn't running, but at least the symptoms have changed for the first time. Now I just need to figure out what it causing too little pressure in the lower chambers of the FD, or if somehow the plunger is sitting higher than it should.

    There is no visual indication that there is anything wrong with the FD - it is not leaking, and the plunger moves freely and gradually as it should. The only things that have changed in the past week are the new seals, and the fact that the missing seal at the tip of the pressure regulator has been replaced. Although the cold control pressure is still high, at least it is now lower than the system pressure.

    Any suggestions as to what might be causing this are very welcome! Thanks so much!

  7. #57
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    Quote Originally Posted by dreiermann View Post
    OK, the o-rings arrived, I replaced all of the old o-rings in the pressure regulator and fuel distributor with new high-durometer Viton o-rings, and re-assembled everything.

    I tested the pressures, and got 35 psi cold control pressure (60 degree ambient) and 65 psi system pressure. However, I had to test very quickly because I could hear the injectors singing. I pulled the plugs, and there was a lot of gas in the cylinders. I cleared out the gas by turning the engine by hand and running compressed air into the spark plug hole (leaving room for it to also come back out of the spark plug hole). Then tried to start it. It did run, chugging and not really getting any revs, but I could still hear the injectors over the sound of the engine because - of course - they were still flowing way too much fuel.

    Disappointing that the car still isn't running, but at least the symptoms have changed for the first time. Now I just need to figure out what it causing too little pressure in the lower chambers of the FD, or if somehow the plunger is sitting higher than it should.

    There is no visual indication that there is anything wrong with the FD - it is not leaking, and the plunger moves freely and gradually as it should. The only things that have changed in the past week are the new seals, and the fact that the missing seal at the tip of the pressure regulator has been replaced. Although the cold control pressure is still high, at least it is now lower than the system pressure.

    Any suggestions as to what might be causing this are very welcome! Thanks so much!
    Have you tried leaning the fuel mix(CCW on the 3mm allen screw) to see if the injectors stop whistling? Keep track of your adjustments, it's very sensitive. If you cleaned the mating surfaces between the fuel dist and meter assy - I could see this making it run richer on fuel than it use to.

    If leaning the fuel mix does not stop the injectors whistling, the o-rings for the four ports may be damaged or improper size. Another possibility is that the metering plate is not centered in it's bore (causing it to stick), or not level at rest position (sitting high).
    Tbd

  8. #58
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    The metering plate is sitting normally and moves up-and-down with the same smooth resistance that it always has, so I can feel that the plunger is moving along with it - especially on the upward travel.

    I will try backing out the fuel mix 3mm, that's a good idea.

    If that doesn't do it, I will open up the FD again and look at the four port o-rings. The ones that I took out looked like they were pushed out-of-shape, but then to get the new ones in it seemed like they probably ended up in about the same shape. The list called for 7.5mm ID, the closest that I could get was 7mm ID, and if anything they still seemed too big. Also, I could not tell any difference in size between the old 7.5mm rings and the new 7.0mm rings. The metering slots are vertical, but by the time I got the metering section nearly all the way into the bore, it looked like the o-rings had been pushed to almost a D-shape (with the flat side on the bottom). This is how the old ones looked when I took them out. If I open up the FD again, what could I use inside of the bore to make it slide together with less 'push' on the o-rings - petroleum jelly? Lithium grease?

    One more thing, on the mating surfaces of the two halves of the FD (where they meet the stainless steel diaphragm), I used thinned-out Indian Head Gasket Shellac. I put it on so thin that it just left a yellowish haze on the grey metal. Do you suppose that the thickness of the shellac could raise the diaphragm enough that there would be a noticeable difference in fuel flow? Other threads I have seen show the mating halves sealed with this shellac, with no mention of any issues.

    Thanks!

  9. #59
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    The o-rings need to be lubricated, all of them because very tight fits (except the o-ring on the control pressure piston). Petroleum jelly should do the trick. Don't use grease. The 7.0mm ID should be fine (assuming the CS is 2mm) as long as you did not have to stretch the o-rings to get them on.

    Just do the same thing with the shellac, don't concern with any 'noticeable difference in fuel flow' from the shellac.
    Tbd

  10. #60
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    Leaning the fuel mixture screw did not quiet the injectors.

    Epmedia - great call on the metering slot o-rings. Some had obviously rolled over the protrusion on the metering slot, I could see two dents in the faces of some of the o-rings. I am greatly relieved to find out where the flooding came from.

    Also, the o-ring at the top of the metering assembly was really damaged - the outer portion was neatly sheared-off. This was a smaller (2.0mm) CS, and it was also a slightly smaller ID (15.0mm vs 15.5mm) than the original. My guess is that when I pressed in the metering assembly, I just pushed it in too far and the edge of the smaller part of the bore at the top sheared it off. I will be more careful next time.

    Probably getting ahead of myself a bit, but assuming that I get everything assembled properly, and the pressures are correct, and after I change the oil (in case gas from the flooding got past the piston rings): when I go to start the engine the bypass air and the mixture screw will not be in the correct position. In a normal tune-up, the bypass air screw would be all the way in (rich), but where should I set the mixture screw for the initial start-up? I was thinking to set it halfway between the limits - or should I just set it back to the last position it was in when the engine was running? Previously, I had set it by ear (at the midpoint between stumbling rich and stumbling lean).

    Again, thanks so much for all the input. Without it, I would be in a serious state of funk. And not James-Brown-funk!

  11. #61
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    You're welcome. The first time I put together a fuel dist, I messed up the same o-rings you did...

    The bypass air screw ?? Do you mean the slotted brass idle adjust screw on the throttle body? This idle adjust screw is not an air adjust screw, it adjusts "metered" air. Metered air flows through the meter assy, and is "in-sync" with the fuel mixture. The engine would not idle if it was screwed in all the way, unless there was a significant vacuum leak and compensated fuel mix setting.

    The o-ring store has all the correct size o-rings.
    Go to post #25 here: https://www.bimmerforums.com/forum/s...Rebuild-How-To

    Don't worry about the flat-slotted idle speed screw. Again, this adjusts "metered air". It has nothing to do with the fuel mix, only engine idle speed. You can temporarily open it a whole turn to help the engine idle.

    *Change the engine oil after attempting to "Re-Adjust Base Mixture Setting".

    Because the 3mm fuel mix screw was previously adjusted to compensate for the high 'control' pressure, I would first turn the 3mm fuel mix screw 1+1/2 turn leaner (CCW) than it's original setting. With the fuel pump jumped, make sure none of the injectors are whistling, lean more if necessary. Then attempt to"Re-Adjust Base Mixture Setting" by the procedure in the faq/diy thread.
    Tbd

  12. #62
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    SUCCESS!!! I can't thank you guys enough. Once I finally got time to work on it, everything went very smoothly. I only adjusted it enough to get it running, but it is already much smoother than it was before the dying issue came up.

    I will read the FAQ on adjusting the idle mixture, but I was wondering if the narrow-band O2 sensor (my exhaust manifold is from an '83 and still has the sensor in it) is sensitive enough for me to use in adjusting the idle mixture. From what I remember, the earlier O2 sensors were more of an on-off device than a modulating device, but maybe that will be enough. EDIT - right after I wrote this, I went to the FAQs and it has the procedure for doing this.

    One other thing that I wanted to mention for anyone else going through their fuel system - when cleaning the throttle body I saw that the roller for the throttle quadrant had a groove worn into it from the quadrant. The roller was thick enough to flip so that the quadrant does not get caught in the groove anymore. Now that the car is running, I can feel the difference at the pedal. I will make it a regular practice to keep that roller lubed so that it doesn't happen again.

    To summarize, the only real "wrong" things I found were a missing o-ring at the tip of the pressure regulator, and some pinholes in the metal Y-fitting at the fuel pump inlet (where drip line from the accumulator attaches). My fuel pump may have been on the way out, but it seemed to have good pressure. I am still not entirely sure what exactly caused the dying-after-four-seconds issue. If it was the o-ring at the tip of the pressure regulator, I cannot imagine how that o-ring escaped.

    Thanks again, everybody!
    Last edited by dreiermann; 05-22-2017 at 10:19 AM.

  13. #63
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    Update - after enjoying the newly smooth-running engine for a couple of days at around-town speeds, I found a road where I could get it up to 60. Afterwards, it had a high and rough idle. The high idle went away when I tightened the oil cap, but the rough idle was apparently due to cylinder 3 not firing (as determined by removing spark plug wires). I put a spare hose onto the FD at the number 3 connection, and no fuel came out while the engine was running. I am pretty sure that I will need to open up the FD again and check everything, but if anyone has any other thoughts/comments, they are appreciated. Thanks!

  14. #64
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    Quote Originally Posted by dreiermann View Post
    Update - after enjoying the newly smooth-running engine for a couple of days at around-town speeds, I found a road where I could get it up to 60. Afterwards, it had a high and rough idle. The high idle went away when I tightened the oil cap, but the rough idle was apparently due to cylinder 3 not firing (as determined by removing spark plug wires). I put a spare hose onto the FD at the number 3 connection, and no fuel came out while the engine was running. I am pretty sure that I will need to open up the FD again and check everything, but if anyone has any other thoughts/comments, they are appreciated. Thanks!
    See if the little cone shaped filters are still installed under the injector line banjo bolts on the fuel dist. They are hard to see, drying out the ports helps for visual. If installed, can be removed with a tiny screw driver or torx bit with a gentle upward twist. Some folks don't even use those filters because they are very finicky and sometimes more of a pain to service than the injectors..
    Tbd

  15. #65
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    Epmedia -

    Excellent thinking on those little filters, and thanks for that tip! I removed the filter for Number 3, and it was slightly dirty (still surprising since I had just cleaned the entire FD). With the newly-cleaned cone filter installed, Number 3 had no gas coming out at idle, and only a dribble when revved to 3,000 RPM. Removing the cone filter entirely only made the dribble a little faster - still no fuel at idle. In any case, at no point did it look like it could overcome the 40 (?) psi that the injectors need to open.

    My next step will be to check system pressure (maybe the overall pressure is low and Number 3 is just the weakest link), look at the pressure regulator (which had the o-ring issue when I first took it out), and then open up the FD to make sure that it is clean.

    The only thing that I can think of that could possibly cause a problem inside of there would be bits of rubber from previously-damaged o-rings, or squeezed-out gasket shellac - even though I had thinned it way down before painting it onto the FD halves.

  16. #66
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    You can try enriching the fuel mix 1/16 turn (CW) to see if fuel comes out the line. It's possible it's just set too lean and the inner port on #3 is just not quite open at idle. There's not much fuel flow in the injector lines at idle/no-load and the fuel pressure in the injector lines is always constant when the engine is running.
    Tbd

  17. #67
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    Does it get better if it warms up/cools down?
    -John

  18. #68
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    I think that I have found the problem, but not quite sure of the solution.

    Upon opening the FD, I found that the high-durometer Viton O-ring on the lower part of the metering assembly sheared off where it met the lower half of the FD body, spreading high-durometer shrapnel throughout the FD. Also, the gasket shellac had gone farther than it should have, in spite of having thinned it down quite a bit and kept it away from the edges of the hemispheres. Still, I did not see any obvious blockage of the port for cylinder 3, but I suppose stuff could have been floating around.

    This is the second time that the o-ring has sheared, but I thought that I had fixed that problem by using petroleum jelly prior to assembly. Now, I am not sure how to assemble the FD without making that o-ring kaput. The edge where the lower half of the FD hits the o-ring has a fairly sharp edge at the shoulder, maybe I should round that over a bit. It seems like the o-ring sits entirely past that edge, so rounding it should not affect sealing. I am wondering if the 'high-durometer' aspect is making it more prone to shearing. And I am trying to remember if the one I took out originally was sheared in the same way, too.

    As for the little cone filters, I am glad that they were there because they had prevented some of the junk from getting to the injectors.

    And it is good to have a long weekend to (hopefully) get this wrapped up!

  19. #69
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    Good news - FD is rebuilt and car is back to running smoothly. Two things that I did differently - 1) I smoothed over the edges (by hand with a small polishing stone) where the bore for the metering assembly changes diameter in the lower half of the FD, with a test-fit to make sure that it didn't shear the o-ring like before. 2) I did not use any sealant at all (previously had used gasket shellac). Just polished the surfaces and diaphragm by hand with silver polish and a paper towel. I kept the cone filters, rinsing them off with Gumout cleared them up.

    Once it was all back in, I had to richen the fuel mix by a full turn, I am assuming that this is because assembling without the gasket shellac brings the diaphragm closer to the ports. No leaks after several test drives, and it idles very smoothly now. Hopefully, it will stay that way for a while now so I can move on to other projects on the car!

    Thanks again to all who helped, especially Epmedia!

  20. #70
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    No problemo and Good Job !
    Tbd

  21. #71
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    Wow, congrats! I'm shocked it doesn't leak without any sealant on it! I'm not sure I'm brave enough to try taking mine apart.

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