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Garage => Mechanicals => Topic started by: Feather535 on 18 December 2022, 08:27 PM

Title: Inside the WUR
Post by: Feather535 on 18 December 2022, 08:27 PM
I'm disassembling the WUR from my 280SE in search of the cause of excessively high control pressure (always about 5.5 bar, warm or cold).  I suspect a restriction on the return side and according to raueda1 there is a little screen inside the WUR that can get clogged and cause that to happen.

I've removed the bimetal strip, the springs and the little pushrod, and the circular cap and 4 screws beneath that.  Under that is a steel cylinder: on the inside face is a small diaphragm, and the fittings for the fuel lines screw into the outside face.  But now I don't know what to do.  It's not obvious how to remove the diaphragm, and I still don't see where the fuel comes into the WUR and goes out.   In fact, from the outside, the port for the return line looks like a dead end, while the one for the inlet has a small orifice at the bottom.

A diagram of this device would be a big help.  Can anyone explain how to get access to the fuel passages and that screen, if it's really there?
Title: Re: Inside the WUR
Post by: daantjie on 18 December 2022, 10:00 PM
Here is a good video that'll help you:

https://m.youtube.com/watch?v=VVsnF2RlEqw

Title: Re: Inside the WUR
Post by: raueda1 on 21 December 2022, 06:17 PM
Check out this (https://forum.w116.org/index.php?action=dlattach;attach=13050) courtesy of Daniel from another post.
Title: Re: Inside the WUR
Post by: Feather535 on 21 December 2022, 11:27 PM
Quote from: daantjie on 18 December 2022, 10:00 PMHere is a good video that'll help you:

https://m.youtube.com/watch?v=VVsnF2RlEqw


Kent from Mercedessource has also done a pretty good video that's a lot shorter https://www.youtube.com/watch?v=UoNw47wI8E8
Title: Re: Inside the WUR
Post by: Feather535 on 21 December 2022, 11:33 PM
Now I've taken most of the WUR apart and I can see that the screen inside the large fuel fitting is plugged up. It's so bad that at first I didn't recognize that actually is a screen.  But it's hard to see how to get access to the screen to clean it. Seems like the fuel cell would have to come out, but it's not clear how to remove the fuel cell or whether even that would make the screen accessible.  Ideas?
Title: Re: Inside the WUR
Post by: ramiro on 22 December 2022, 06:48 AM
I usually just blow throught it with compressed air from the other direction.
Removing the fuel cell will not change the access i think , but removing the fuel cell will change the pressures because the warm control pressure is adjusted by tapping in or out the fuel cell , allthough i am pretty sure it has to be readjusted after dissasembly anyway.
Title: Re: Inside the WUR
Post by: raueda1 on 22 December 2022, 01:57 PM
Quote from: ramiro on 22 December 2022, 06:48 AMI usually just blow throught it with compressed air from the other direction.
Removing the fuel cell will not change the access i think , but removing the fuel cell will change the pressures because the warm control pressure is adjusted by tapping in or out the fuel cell , allthough i am pretty sure it has to be readjusted after dissasembly anyway.

Yes, all this.  A couple further points.  The steel diaphragms really need to come off the cylindrical fuel cell to clean it all out, but I guess this is already done.  So, also try using carb cleaner to loosten the junk inside filter.  It might be time to just buy a rebuild kit.  They're available on ebay.  Then you can also replace the o-ring under the diaphragms as well as the diaphragms themselves.  If the diaphragms are slightly distorted or bent (pretty likely after years of use) then they should be replaced.

As for knocking out the cell, you might as well just do it.  It's almost certain that it will need to be reset anyway, so why not?  Then you can also repolish the bottom per link above.  Use 3000 grit paper to get a mirror finish.  Take a picture so you know approximate cell positioning when putting it back together.  And don't get discouraged.  You'll likely do a lot of in-and-out-again before getting pressure set up right.  That's just a fact of life (and also why there are so many posts about making your WUR adjustable).  Keep posting progress!
Title: Re: Inside the WUR
Post by: raueda1 on 22 December 2022, 03:56 PM
There's also this one:
[another wur video]https://www.youtube.com/watch?v=zW5qV208tCA[/url]

This guy polishes the screw-on valve cell cover but not the face of the valve body itself (where the orifices are).  Seems a but odd - pressure will doubtless need resetting, so why not do the whole job?
Title: Re: Inside the WUR
Post by: SteveDuNord on 25 January 2023, 09:38 AM
Does anybody know where I can buy the retaining clip for the electrical connector to the WUR?

I appear to have lost mine.
Title: Re: Inside the WUR
Post by: Feather535 on 29 January 2023, 12:32 PM
Quote from: raueda1 on 22 December 2022, 01:57 PMYou'll likely do a lot of in-and-out-again before getting pressure set up right.  That's just a fact of life (and also why there are so many posts about making your WUR adjustable).  Keep posting progress!

Sadly, that seems to be what's in store.  Since my last post, I replaced the o-rings in the fuel distributor using the kit from raueda1, removed and disassembled the WUR, soaked it in solvent for 2 weeks, and put it back together using the kit from k-jet.biz.  At first, the screen on the inlet side of the WUR was obscured with sediment, but after cleaning it looked clear and I could blow compressed air through the fuel cell fittings. 

I was feeling optimistic that clearing the screen would fix my problems, but when I reinstalled the WUR yesterday, nothing had changed  :-X That is, the control pressure is 5.5 bar warm or cold and the engine runs lean.

So what next?  Push in the pin holding the bimetal strip?  Replace the pressure damper in the inlet circuit?  Reset the fuel cell height?  Take the WUR apart again?  It seems like I'm starting over from zero.
Title: Re: Inside the WUR
Post by: revilla on 29 January 2023, 03:22 PM
Hi,
Can you send us a picture of your pressure gage setup when measuring both control and system pressure. With that kind of CP your engine wouldn't even start. The piston won't move even one mm upwards to let fuel flow into the injectors. Do not hammer the plates/pins for now. That might get things worse if we don't understand what's going on with the measurement method first.
Title: Re: Inside the WUR
Post by: Feather535 on 29 January 2023, 08:34 PM
Quote from: revilla on 29 January 2023, 03:22 PMCan you send us a picture of your pressure gage setup when measuring both control and system pressure. With that kind of CP your engine wouldn't even start.

The engine does start, but not easily, and it's clearly running much too lean. 

I'll post a picture as soon as I can figure out how.
Title: Re: Inside the WUR
Post by: Feather535 on 29 January 2023, 08:38 PM
(https://share.icloud.com/photos/0ceCLWx_G7oPh5DdIu_i4XPOQ)

I hope this is clear enough.  The valve is on the hose connected to the hard fuel line to the WUR.
Title: Re: Inside the WUR
Post by: Feather535 on 29 January 2023, 08:39 PM
(https://share.icloud.com/photos/0ceCLWx_G7oPh5DdIu_i4XPOQ)
Title: Re: Inside the WUR
Post by: rumb on 30 January 2023, 09:19 AM


I'll post a picture as soon as I can figure out how.
[/quote]


You need to use reply, not quick reply, then use the paperclip icon to upload.
Title: Re: Inside the WUR
Post by: Feather535 on 30 January 2023, 10:43 AM
IMG_4284.jpegIMG_4284.jpeg 

Thanks.  Let's see if this works.
Title: Re: Inside the WUR
Post by: revilla on 30 January 2023, 12:36 PM
Your setup looks correct.
This is what I'll do, if you decide to do this test please be very very careful. If you're not confortable with it please don't try.
Engine off, key in position 1, disconnect blue connector on FD. Pump is now running. Look at your gage. Very slowly unscrew the return line at FD head. Very very slowly with a rag underneath to capture fuel. When the first drops start leaking, does the pressure go down? Let more fuel out, pressure goes lower? If yes, you have a blocked return line. Go closer to the tank you should hear fuel flowing into it. Repeat the same exercise after reconnecting the return line but this time unscrew the fuel pressure regulator (16mm wrench) on top/front of your FD. Very slowly again until first drops leak. Lower pressure? Unscrew more but never completely. Pressure goes down? Same exercise but this time with the 12mm line on the side of the pressure regulator. With pump running you should see fuel flowing out. If not, either the orings inside the regulator are damaged (there are a total of 3: tip, middle body, small inner chamber), or the guts of your FD need to be rebuilt. The WUR is the other option, but I have never seen this extreme CP >5bars situation before related to WUR adjustment.
In your other post you asked about how to set this up. You don't need to reopen the WUR as you're dealing with a high pressure issue. You need to tap that insert that connects the bimetallic strip and the "valve". Basically tap it inward so the gap between the WUR top surface and the insert increases. Essentially you are "opening the valve" to let more fuel pass through decreasing therefore the CP. Before tapping, observe and measure the gap between surface and insert. For a CP >5bars so should have zero mm gap. Tap very carefully but firmly. The insert is solid but sensitive at the same time. If you overdo CP will then be too low. Then you'll need to tap it outward from the inside of the WUR. This can be painful with multiple iterations, but this how we learn the mechanics of how things work. This is a trial, measure, error type approach. Measure that gap with a digital caliper if possible. You're looking at 1-2mm no more. This is assuming the guts of your WUR were correctly assembled. I'm a bit worried with the part where you blew compressed air through those ports. The metal plate is so delicate, hope it's not damaged. Worse case send it out for repair/calibration. Plenty of sources for that in the US.
Please keep us posted.
R
Title: Re: Inside the WUR
Post by: daantjie on 30 January 2023, 01:25 PM
I feel for you guys with the 280 engine, the WUR is in such a crap location!  On the V8 it could not be easier to access.
Title: Re: Inside the WUR
Post by: Feather535 on 31 January 2023, 10:02 PM
Un grand merci Robert.  I will do these tests, but I have one question.  Where you say

Quote from: revilla on 30 January 2023, 12:36 PMSame exercise but this time with the 12mm line on the side of the pressure regulator.

do you mean the smaller fuel line just to the rear of the 16mm fitting on the pressure regulator?

No need to worry about the thin steel diaphragm in the WUR, by the way.  It was removed when I blew air through the ports, and I replaced it with a new one anyway.

I'll do the tests and report back.  Wish me luck!
Title: Re: Inside the WUR
Post by: Feather535 on 31 January 2023, 10:08 PM
Quote from: daantjie on 30 January 2023, 01:25 PMI feel for you guys with the 280 engine, the WUR is in such a crap location! 

Yes, it's awful!  One of the worst locations for a critical component on any car I've worked on: difficult to see, let alone reach with tools.  And filthy, at least on this particular car.

In one of his videos, Kent from mercedessource.com shows how he relocated the WUR on an M110 to a place behind the fuel distributor.  That would be a huge improvement.  I could probably fabricate a bracket and reroute the wiring and vacuum lines, but I don't know what I'd do with the hard fuel lines. 
Title: Re: Inside the WUR
Post by: revilla on 01 February 2023, 12:58 AM
Quote from: Feather535 on 31 January 2023, 10:02 PMUn grand merci Robert.  I will do these tests, but I have one question.  Where you say

Quote from: revilla on 30 January 2023, 12:36 PMSame exercise but this time with the 12mm line on the side of the pressure regulator.

do you mean the smaller fuel line just to the rear of the 16mm fitting on the pressure regulator?


Yes, exactly that line.
Title: Re: Inside the WUR
Post by: revilla on 01 February 2023, 01:07 AM
Quote from: Feather535 on 31 January 2023, 10:08 PMIn one of his videos, Kent from mercedessource.com shows how he relocated the WUR on an M110 to a place behind the fuel distributor.  That would be a huge improvement.  I could probably fabricate a bracket and reroute the wiring and vacuum lines, but I don't know what I'd do with the hard fuel lines. 

Haven't seen the video, but that's what I've done years ago.
Vacuum line = no problem
Wire harness blue connector = no problem
Plastic FOT vacuum = no problem
In/Out fuel lines I replaced them with fuel hoses.
Fuel pulse damper was also relocated next to FD (1977 model) MB already relocated that damper after Model/Year 1978 so my 79 has it next to FD already.
Title: Re: Inside the WUR
Post by: Feather535 on 02 February 2023, 03:28 PM
OK, I did the 3 tests Robert suggested.  CP stays above 5 bar when the main return line and the smaller return line to the WUR are loosened and fuel starts to flow out.  Loosening the 16mm fitting on the FD does cause the pressure to drop, on the other hand.  The more it's loosened, the lower the pressure goes. This also causes the pump to run faster, probably trying to maintain pressure. 

So what does this mean?  I already replaced the 3 o-rings on the assembly attached to that 16mm hex head.
Title: Re: Inside the WUR
Post by: revilla on 02 February 2023, 04:35 PM
Hi,

You have isolated your issue (pressure regulator PG).

Please take pictures and post them here.

Probable causes:
- Wrong O-Rings used.
- Wrong re-assembly.
- Too many shims. How many you have in there? Are all of them 0,1mm type?
- Wrong large spring, unlikely I know.

Title: Re: Inside the WUR
Post by: Feather535 on 02 February 2023, 10:03 PM
Quote from: revilla on 02 February 2023, 04:35 PMYou have isolated your issue (pressure regulator PG).

Probable causes:
- Wrong O-Rings used.
- Wrong re-assembly.
- Too many shims. How many you have in there? Are all of them 0,1mm type?
- Wrong large spring, unlikely I know.

Looks like progress at last! 

Before taking it apart, I'll guess that wrong o-rings and wrong reassembly are not the problem, since the CP was the same before I replaced the o-rings.  But I'll post pictures and we'll see!
Title: Re: Inside the WUR
Post by: Feather535 on 04 February 2023, 04:37 PM
There are 2 threads going on this topic, so to avoid further confusion, I'm starting a new one combining this one and "WUR fuel cell height and control pressure".  Stay tuned.