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Garage => Mechanicals => Topic started by: Feather535 on 05 February 2023, 11:46 AM

Title: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 05 February 2023, 11:46 AM
I initiated 2 threads related to excessive control pressure that had grown to multiple responses over 2 pages.  To reduce confusion going forward, I'm starting a new topic, beginning with a summary of the problem and what I've done so far. This is part 1.

The car in question is a 1977 280SE, sold new in Los Angeles California.  It hadn't been  on the road in 10 years when I acquired it.  The seller had replaced the fuel pump and filter, distributor cap, spark plugs and wires and got the engine running, but the car wasn't drivable.

The problem I'm trying to solve is lean running.  The engine is hard to start cold.  When it does start, it pops back through the airflow plate and dies if the throttle is opened.  When the weather was warmer, I could keep the engine running long enough to reach operating temperature and then it ran well enough to drive at low speed. I haven't been able to do this now with cold weather and snow.

Before considering fuel injection, I eliminated other potential causes, mainly vacuum leaks and ignition timing. 

The fuel delivery volume is adequate and base system pressure is 5.5 bar. The cold start injector is working. I have gone through the rest of the test sequence in the CIS Diagnosis and Adjustment manual and it passes all tests except these: cold control pressure = 5.5 bar, warm control pressure = 5.5 bar, full load vacuum enrichment 5.5 bar.

Since then I removed the WUR, disassembled it, cleaned the screen on the inlet side and reassembled it with new parts from k-jet.biz.  Because the inlet screen was visibly plugged with sediment, I was optimistic that this would restore the correct CP, so I didn't try to reset the fuel cell height, which is about 2 mm above the WUR surface.

Now the WUR is back on the car, but nothing has changed: CP is still basically the same as system pressure.

This is already long, so I'll describe the latest tests in Part 2.

Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 05 February 2023, 12:01 PM
This is Part 2.  The cleaned and reconditioned WUR is back on the car, but control pressure is still 5.5 bar cold.  The engine won't run long enough to test warm CP. 

revilla recommended 3 tests "Very slowly unscrew the return line at FD head...does the pressure go down? Repeat the same exercise...but this time unscrew the fuel pressure regulator on top/front of your FD. 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." 

When I do this the CP stays the same for the first and third tests on the return lines, but it goes down when the fuel pressure regulator assembly is loosened, going lower the farther it's unscrewed.  revilla thinks the FP regulator is the source of the problem and asked for a picture; here's one, and I can provide more. I replaced all the o-rings with new ones from raueda1.  There are 2 shims on the assembly.  I don't have a micrometer, but one is thin and the other is thick, about 1 mm.  And that's where it stands today...
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: revilla on 05 February 2023, 10:35 PM
Hi
Did you touch/change the 3rd and more difficult o-ring inside the chamber (allen hex screw) which is attached/sealed to the bottom of the small shaft? If yes, wad the tiny little clip that holds the nut and assembly together place back correctly? Does the shaft move freely?
What do you see inside that chamber when depressing the shaft? There are 3 lateral little holes to watch inside the chamber with light and magnifier.  3rd O-ring intact and in place, sealed to the bottom of the shaft?
Can you repeat your exercise of running the pump and unscrewing the 12mm line? Are you sure there's nothing coming out. Unscrew more and more (be careful). This line connects to the WUR which regulates CP, there should be fuel flowing there with pump running.
When you unscrewed the PR, how many turns, how much fuel and what do you read as CP? Does the car start with that lower CP (richer mixture). Careful with that fuel leaking, make sure you start with a dry rag and your ignition coil and cables are out of the way. If you aren't comfortable with this experiment please don't proceed.
The hypothesis we're testing is CP = SP = 5.5bars because the insides of the PR is blocking fuel from flowing to/from WUR. There are only 3 choices here (yes, no, partially). Need your results to continue or abort this hypothesis.
Have you cleaned the pass from PR chamber to 12mm lateral line? Open? Free? Again, with pump running there SHOULD be fuel leaking there. If not, we need to look closer to that line and inside PR. When you blew air through that WUR line, was is free flowing? Something is blocking fuel flow there? Let's find out what...
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 09 February 2023, 10:25 PM
Quote from: revilla on 05 February 2023, 10:35 PMDid you touch/change the 3rd and more difficult o-ring inside the chamber (allen hex screw) which is attached/sealed to the bottom of the small shaft? If yes, wad the tiny little clip that holds the nut and assembly together place back correctly? Does the shaft move freely?
What do you see inside that chamber when depressing the shaft?...
Can you repeat your exercise of running the pump and unscrewing the 12mm line?

I did replace the interior o-ring.  The tiny c-clip is in place and the shaft moves freely.   I checked that the holes on the sides are clear, but haven't looked inside.  I'll do that and then check again for fuel when the 12mm fitting is loosened. 
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 09 February 2023, 10:34 PM
Quote from: revilla on 05 February 2023, 10:35 PMThe hypothesis we're testing is CP = SP = 5.5bars because the insides of the PR is blocking fuel from flowing to/from WUR. There are only 3 choices here (yes, no, partially). Need your results to continue or abort this hypothesis.

Understand the hypothesis and will go through the steps and report back. 

But we haven't talked about the inlet side of the WUR.  Seems like blockage in the inlet lines, the damper or the screen in the fuel cell could also cause high CP.  But if fuel is coming out, it must be going in, so this hypothesis could be ruled out if fuel comes out of the return line at the PR with the pump running.  Correct?
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: revilla on 10 February 2023, 12:28 AM
Correct.
If fuel doesn't flow out we'll look for the blockage upstream and downstream. Could be the inlet at wur, the be plate itself (valve), the inside of your FD, etc. We need to systematically look at every piece on the path. We'll find the problem.

Ps.: that little o-ring inside, are you sure is the correct size?
Its id/od/thickness are so precise! This thing is "like heat fusioned" to the bottom of the shaft from factory. If it moves it's disaster...
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: raueda1 on 10 February 2023, 08:35 AM
Quote from: revilla on 10 February 2023, 12:28 AMCorrect.
If fuel doesn't flow out we'll look for the blockage upstream and downstream. Could be the inlet at wur, the be plate itself (valve), the inside of your FD, etc. We need to systematically look at every piece on the path. We'll find the problem.

Ps.: that little o-ring inside, are you sure is the correct size?
Its id/od/thickness are so precise! This thing is "like heat fusioned" to the bottom of the shaft from factory. If it moves it's disaster
...
I'll jump in on this.  OP got the o-ring from me.  I got a small lot of them and put one in my car after various CIS annoyances. See this (which may also be of interest to OP) (https://forum.w116.org/mechanicals/primary-fuel-pressure-regulator-is-disassembly-possible/) In hindsight I was surprised that this issue hadn't been discussed here that I could find. Hope this helps and cheers,
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 13 February 2023, 05:43 PM
I did a few more things. 

1. I removed the needle assembly from the FD again and checked the 3 small holes at the top to see if light could pass through.  It did, with or without the spring depressed, so I took it apart again and found the o-ring inside had come loose from its slot.  The original one had been stuck tight to the shaft and I unfortunately tore it up getting it off. 

2. Before putting the assembly back in the FD, I blew compressed air into the return port for the WUR and it came out the port where the needle goes, so apparently no blockage there.

3. With everything back in place and the fuel pump running, system pressure and control pressure are still the same -- but lower then usual: 4.8 bar instead of 5.5, which they always were before.  Strange!

4. I verified that fuel comes out when the 12mm fitting for the WUR return on the FP is opened.  But does this necessarily mean fuel is passing through the WUR and coming back? 

5. Loosening the needle assembly (16mm wrench) with fuel leaking will bring CP down to about 3.8 bar, but apparently no lower.  The engine will start and run in that condition.

For what it's worth, the ambient temperature was warmer when I did all this: about 10C (50F), instead of freezing.

This is a lot of data, but it hasn't gotten me closer to a solution yet.  I'll think about it, but hope you guys have some ideas. 
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 13 February 2023, 08:02 PM
Quote from: Feather535 on 13 February 2023, 05:43 PM3. With everything back in place and the fuel pump running, system pressure and control pressure are still the same -- but lower then usual: 4.8 bar instead of 5.5, which they always were before.  Strange!

4. I verified that fuel comes out when the 12mm fitting for the WUR return on the FP is opened.  But does this necessarily mean fuel is passing through the WUR and coming back? 

Never mind number 3.  I discovered one of the shims had fallen out when I removed the needle assembly.  It's back in now and system pressure is back to 5.5.  So is CP.

To address my question in 4, I tried removing the 12 mm fitting on the FP again.  With the pump running and the gauge valve open, fuel is coming out of the port on the FD, not the line connected to the WUR.  I did the same test at the WUR end (small fitting) and verified that fuel is coming out of the line to the FD, not the small port on the WUR. 

Unless I'm confused about which way fuel flows through the control pressure circuit, this seems backwards.  I understood fuel should flow from the top of the FD, through the damper and into the big fitting on the WUR and return from the small port on the WUR to the small port on the side of the FD before going back to the tank.   Is this wrong?

Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: ramiro on 15 February 2023, 11:59 AM
Yes the big fitting on WUR is the flow from the FD and the small is the return to the tank.
So you have fuel comming out at the WUR return port at the FD ?
I think that it is normal that fuel comes there out because it is also connected to the main FD return line to the tank but it shouldn't have any pressure.
Also if you turn the pump ofo there will be pressure because the return closes and the WUR will have pressure on both lines.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 17 February 2023, 03:07 PM
Quote from: ramiro on 15 February 2023, 11:59 AMSo you have fuel comming out at the WUR return port at the FD ?
I think that it is normal that fuel comes there out because it is also connected to the main FD return line to the tank but it shouldn't have any pressure.

I suppose this makes sense, but there is no fuel coming out of the return port on the WUR with the pump running.

Wouldn't this mean that either 1) fuel isn't reaching the inlet side of the WUR or 2) it isn't flowing through the WUR?
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: ramiro on 17 February 2023, 04:51 PM
Just check if fuel is coming out the inlet(the one with the filter on the WUR) , if yes there is no fuel flowing through the WUR .
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 21 February 2023, 10:18 PM
I've done a few more things since my last post.   

1. Disconnected the inlet and outlet lines on the WUR one at a time and verified fuel is reaching the WUR and exiting it.  Control pressure is still too high, though—about 5.5 bar warm or cold—so I conclude the WUR could be partially, but not completely blocked. 

2.  Took the WUR apart again and cleaned it with solvent and compressed air.  While it was out, I pushed the fuel cell upward in the WUR body.  Before, only about 1 mm of the fuel cell was exposed; now it's about 4 mm. Also verified that the heater on the bimetal strip does actually get hot and that its resistance is in spec.   

3. Instead of reinstalling the WUR in its normal, inaccessible place under the M110 intake manifold, I rigged it up as shown in the picture so it's easy to remove and reinstall. 

4. First, I tested CP without the springs or the heater installed, so the WUR is basically just the shell of the top half holding the fuel cell. The gauge reads 0.7 bar and fuel is clearly flowing back to the tank—so progress there.

5. With the WUR reassembled and the fuel pump running, but no electricity or vacuum connected, the CP is still 0.7 bar, so in spec for the ambient temperature at the time (47 F, 8 C).

6. But, with the WUR's heater connected and the fuel pump-but not the engine—running, CP still doesn't increase, even after 10 minutes. 

Now, I guess this could be because at 8 C the WUR's internal heater alone, without engine heat, doesn't raise the temperature enough to change the spring pressure.  But it could also be because now the fuel cell is too high relative to the spring assembly.

So my dilemma is whether to punch the fuel cell down 1 mm or so and test again with the current setup or reinstall the WUR in its regular position (a nasty, time-consuming job) so I can start the engine and test warm CP with the whole system operating as normal.

Seeking the forum's advice while I contemplate next steps.

IMG_4299.jpeg
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: ramiro on 22 February 2023, 04:34 AM
I can confirm that even at below 0 C the electric Heater is enough to let the pressure rise just takes longer , but you can also take a heat gun to assist it.
It's no clear in the Picture but for me it looks like the pin that holds the bimetal strip is nearly at the top , that would explain why you pressure doesn't rise.
If it's not at the top i would suggest to tap it to the top and then adjust the fuel cell until you reach your warm pressure(i would go 0,2 - 0,4 bar lower first and make sure it is not rising more when you put the WUR back to its place) then you can adjust the cold pressure by tapping the pin for the bimetal strip in.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 22 February 2023, 10:34 AM
Quote from: ramiro on 22 February 2023, 04:34 AMit looks like the pin that holds the bimetal strip is nearly at the top

You're right, the pin with the bimetal strip is down about 1 mm.  I will try again after tapping it all the way to the surface.

I did use a heat gun on the WUR.  It didn't cause the pressure to change, but maybe I didn't heat the WUR enough.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: ramiro on 22 February 2023, 11:27 AM
If it's so far up it is normal that the pressure is not rising because the bimetal has no effect like that , and thats also the purpose because you can now adjust the warm pressure to ~ 3,2 by tapping the fuel cell in and then you can lower the pressure down with the bimetal.

The idea is that the bimetal strip should have no effect when the engine has warmed up thats why you should tap it out to adjust the warm pressure to be sure that it won't mess with the pressure and only then adjust the cold pressure.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 26 February 2023, 05:06 PM
I followed this procedure.  First I drove the pin for the bimetal strip up to be flush with the top of the WUR, then tapped the fuel cell down about about 2 mm above the top (starting at 4 mm), then tapped the pin for the bimetal down again.  Now I have 0.9 bar cold at about 3 C and 3.1 bar warm after 6 minutes with the heater plugged in and using a heat gun on the outside of the WUR for a few more minutes. Both settings are in spec for the temperature when I did this (3 C) and the model (California, 1977), so this should be good enough.

Now I need to put the WUR back in it's normal place and see how the engine runs, but that's a job for a warmer day!
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: ramiro on 26 February 2023, 06:21 PM
I hope that you measured the pressure and adjusted it to the around 3.1 bar before you tapped the pin back in, because if not it is possible that the bimetal is affecting you warm pressure and it could rise further on a hot engine (i made this mistake before knowing the procedure and nearly went crazy because the warm pressure was always changing).
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 27 February 2023, 12:13 PM
Quote from: ramiro on 26 February 2023, 06:21 PMI hope that you measured the pressure and adjusted it to the around 3.1 bar before you tapped the pin back in

That's how I did it.  I had 3.2 without heat before tapping the pin down and 3.1 with heat afterward.  Seems good?
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: ramiro on 27 February 2023, 04:38 PM
Should be good then , i don't know if you have full throttle enrichment on the WUR if yes then this is the full throttle control pressure , so at no load it will be ~ 0.2 - 0.4 higher , because the vacum is pushing the control rod up.

You can use a vacum pump on the top vacum connector to replicate this without the engine running.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 28 February 2023, 12:41 PM
Quote from: ramiro on 27 February 2023, 04:38 PMShould be good then , i don't know if you have full throttle enrichment on the WUR

It does have full throttle enrichment.  Pulling vacuum makes the pressure drop.  I didn't record the pressure with vacuum, but it's moving in the right direction, so the mechanism seems to be working. 

Next step is to test it on the car with the engine running, but I'll need to wait for the snow to stop.  Can't even get to the garage today!
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: ramiro on 28 February 2023, 04:26 PM
The vacum makes the pressure higher and when the engine is at load there is no vacum in the intake so the control pressure will decrease.
The vacum port is at the top , the other at the bottom is just the vent port that goes before the throttle body.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 28 February 2023, 09:43 PM
Quote from: ramiro on 28 February 2023, 04:26 PMThe vacum makes the pressure higher and when the engine is at load there is no vacum in the intake so the control pressure will decrease.

Of course.  I'll check it again.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 06 May 2023, 07:08 PM
I've been offline for a while because I haven't had much time for working in the garage.  But recently I drained, removed and cleaned the fuel tank (1977 280 SE, California model) and replaced the screen in the bottom of the tank, the accumulator, the filter, and all the hoses in the rear of the car.  Before that, I had removed the WUR (again) and cleaned it (again) after discovering that the inlet was full of sediment (again). 

So today I finally put the WUR back on and tested the pressure.  I was hopeful, because I had gotten it about right earlier this year (1 bar cold, 3.8 running) after thoroughly cleaning and recalibrating the WUR.  But then the cold pressure crept up to where it had before (5.2 bar) after running the engine for a little while.  I thought this must have been because the inlet was clogged again.

But no luck.  The cold pressure is still 5.2 bar, even with nothing installed inside the WUR except the diaphragm, and with the fuel cell standing about 5 mm above the top of the WUR. 

Gotta say, I'm getting pretty tired of this. 
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: ramiro on 07 May 2023, 08:25 AM
If even without anything inside the pressure is 5.2 bar something must be clooged , either the return line or something that got behind the mesh in the WUR.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: daantjie on 07 May 2023, 10:48 AM
Might be time to swap in a known good WUR.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 07 May 2023, 11:59 AM
Quote from: daantjie on 07 May 2023, 10:48 AMMight be time to swap in a known good WUR.

That's what I'm thinking.  Unfortunately, I don't have one and don't know anyone nearby who does, so that probably means buying a refurbished unit. 
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: daantjie on 07 May 2023, 03:22 PM
Quote from: Feather535 on 07 May 2023, 11:59 AM
Quote from: daantjie on 07 May 2023, 10:48 AMMight be time to swap in a known good WUR.

That's what I'm thinking.  Unfortunately, I don't have one and don't know anyone nearby who does, so that probably means buying a refurbished unit. 

Sometimes you can find a NOS one on ebay but usually they are priced quite high.  Also need to make sure to get the right one as there are many variations over the years and models.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Randys01 on 08 May 2023, 03:57 AM
I'd be wary of buying a 2nd hand one because it's probably stuffed. caveat emptor.!
You would do better to have yours refurbed. There are several coys near you ie in the USA that do these.....spend the money. You also know that unit is the one for the car [hopefully it's the orig ]

You cannot frig around with the injection on these 50 year old cars like a 3psi Carter on a Chev Belair.!!
The furb unit will last you 20 +years and you can confidently remove it from the list of possibilities going forwrd. What's  more you might get a clue from what they find is wrong with it.




btw .If you suspect crud in the fuel, how do you know the pressure you are reading is not actually fuel pressure build up in the fuel divider?  I gather you've had this WUR apart a 100 times but you need to know is the hi pressure  something to do with the WUR or is a fault further upstream. ? it seems the problem is when it gets warm/hot.the psi rises to full system pressure in stead of a controlled pressure.
It seems the vbalve in the WUR is going nearly to fuully closed. IOf all things arte equal, the only way it do that is if the bi metallic strip is over reacting?


Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 08 May 2023, 10:50 PM
Quote from: Randys01 on 08 May 2023, 03:57 AMIf you suspect crud in the fuel, how do you know the pressure you are reading is not actually fuel pressure build up in the fuel divider?  I gather you've had this WUR apart a 100 times but you need to know is the hi pressure  something to do with the WUR or is a fault further upstream. ? it seems the problem is when it gets warm/hot.the psi rises to full system pressure in stead of a controlled pressure.

Well, there could be crud everywhere in the system, it's true.  But I did a test and found there was fuel going to the WUR but basically none coming out the return, so I concluded the thing had to be clogged.  And actually the COLD pressure is nearly the same as system pressure, even with the springs and bimetal strip removed from the WUR, so those bits aren't the cause.

Only other thing I can think of is a clog in the inlet line or the damper.  I think I tested those too, but will do it again before springing for a rebuilt WUR.

Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Randys01 on 09 May 2023, 02:55 AM
Pardon me if i'm not full bottle on your project but have you had the "slug" apart.?
 If so.    Is the O ring in tact? The foil valve in place? Is the inlet mesh filter crystal clean?
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 09 May 2023, 10:29 PM
Quote from: Randys01 on 09 May 2023, 02:55 AMPardon me if i'm not full bottle on your project but have you had the "slug" apart.?
 If so.    Is the O ring in tact? The foil valve in place? Is the inlet mesh filter crystal clean?

No worries!  Thanks for following this thread.

If the "slug" is the assembly in the picture on page 1 of this thread (I hear it called the fuel pressure regulator), yes, I've cleaned it and replaced all the o-rings.  I also replaced the inlet mesh filter on the fuel distributor and cleaned it again in repeating the whole diagnostic sequence with the WUR.  I don't know what the "foil valve" is. 
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Randys01 on 10 May 2023, 02:45 AM
The slug is the valve body fitted in the WUR to which the inlet and outlet fuel lines are connected. Looking from the inside of the WUR there is a ceramic /fibre type disc with small hole in it. This hole is to allow the pin influenced by the bi metallic strip to adjust the fuel pressure by vituue of a silver film foil and an O ring embedded in side the slug. This assy is held to the slug with 4? screws.
Have you been in here? This is where I think your problem might lie.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: daantjie on 10 May 2023, 11:39 AM
I think I posted this link before, but this is a pretty good overview of what is involved:

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

Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 10 May 2023, 09:48 PM
Quote from: Randys01 on 10 May 2023, 02:45 AMThe slug is the valve body fitted in the WUR to which the inlet and outlet fuel lines are connected.

We're working with different nomenclature here-that assembly is the fuel cell to me-but I did work on it. 

I removed the bimetal strip, springs, hat, pin, the 4 screws and plate and the foil diaphragm and the o-ring underneath.  Then I the soaked the whole assembly in solvent for a week and afterward blew out the orifices with compressed air.  I reassembled the unit with new springs, a new o-ring and a new foil disc.  After all that I was able to get the pressure settings right for a short time, but after starting the engine a couple of times, the control pressure climbed back up to about the same as system pressure.  Since then I've disassembled and cleaned the WUR several more times, but I can't get the pressures back down to where they should be. 

Pretty frustrating, I gotta say.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 10 May 2023, 09:50 PM
Quote from: daantjie on 10 May 2023, 11:39 AMI think I posted this link before, but this is a pretty good overview of what is involved

Yep, watched that and did the whole procedure as described. 
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Randys01 on 10 May 2023, 11:12 PM
ok.,.good man..sounds  very thorough. Seems as tho your pressure  build up is further up the line OR  do you havea full time vacuum line attached to the WUR upper chamber by accident?
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: raueda1 on 11 May 2023, 03:15 AM
This story is very frustrating and I feel your pain. Somehow my gut tells me that there's an odd, recurring problem with crap in the fuel system that keeps clogging things and creating back pressure. 

Are you absolutely certain that the fuel return lines and rubber hoses are clear?  And when you cleaned the fuel tank was there rust silt inside? No doubt there was, but maybe there's residential that is getting stirred up? And have you replaced the rubber return house between the tank and the return line?  Even if you can blow it out with compressed air there can still be enough back pressure to cause problems.  Can't hurt to replace it off you haven't already.

Maybe test a couple things. 1. Disconnect the fuel line at the FD and collect, say, a gallon of fuel in clear container.  Is there any sediment at all?  2. Try the same on the field return.

Also, in cleaning out the slug and replacing the o-ring, did you polish the surface of the slug?  I can't remember if this was discussed.  If not then do so the next time it's apart.  Use high quality 2000 and 3000 grit paper successively to get a mirror finish.  And be sure that's the steel waters or manage or whatever don't have a dimple, otherwise replace. Obviously this won't solve back pressure but the WUR will work better.

I have a feeling that eventually there will be an "ah ha" moment here.  Cheers
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 16 May 2023, 10:16 AM
Quote from: raueda1 on 11 May 2023, 03:15 AMThis story is very frustrating and I feel your pain. Somehow my gut tells me that there's an odd, recurring problem with crap in the fuel system that keeps clogging things and creating back pressure.

That's for sure.  I've been going around in circles chasing this problem for months. 

There was some rust in the tank, but not as much as I expected. The more alarming finding there was the fine-grained tan-colored silt clogging the outlet screen.  It was the same stuff I found in the inlet screen of the WUR after the control pressure started climbing again. 

Of course I replaced the screen in the tank, and the return hose between the hard line and the tank. And just yesterday, I check the rubber return line from the FD to the hard line off (again) and verified that I can blow air through it.  That line is obviously old and doesn't look great;  I'd replace it if I could find a new one, but it's probably ok.

Inside the WUR, the foil disc looked ok when I took it apart for the first time, but I replaced it anyway, along with the o-ring.  But I didn't polish the surface. 

And I haven't collected a fuel sample since cleaning the tank.  I suppose that's worth doing, but sending the WUR out to be rebuilt is beginning to look inevitable.  I'm reluctant to spend the money, but even the factory manual says to test with a known good unit if the CP is too high. 
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: ramiro on 16 May 2023, 02:36 PM
Just a note about sending out them to be rebuilt , in Germany i had 2 WURs send to 2 different companys  1 had to be returned 3 times before the pressure was fine , the other one was completly out of adjustment after 1 year , thats why i started to adjust them myself because spending so much and still having problems is not worth it.

If your control pressure is at system pressure with a empty WUR it really shouldn't be to hard to find the issue i think.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: daantjie on 16 May 2023, 03:14 PM
CIS Flowtech is the go to place for WUR and FD refurb.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 18 May 2023, 02:34 PM
Has anyone used k-jet specialists (www.k-jet.biz) in Australia?  Their service looks a bit cheaper due to the exchange rate.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Randys01 on 19 May 2023, 03:27 AM
Yes. I've used them for WUR and fuel dividers some years back.
I could not speak to their current performance but have no reason to doubt them .

REcon a WUR is... for a pro..., a piece of cake.

The exchange rate is a bonanza for you. It's killing us sending stuff to the US or buying it from there.....and so is the freight either way.!!

As your story has unfolded I'm inclined to think the problem lies not in the WUR but back in the fuel divider.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: raueda1 on 19 May 2023, 07:09 AM
Quote from: Randys01 on 19 May 2023, 03:27 AMYes. I've used them for WUR and fuel dividers some years back.
I could not speak to their current performance but have no reason to doubt them .

REcon a WUR is... for a pro..., a piece of cake.

The exchange rate is a bonanza for you. It's killing us sending stuff to the US or buying it from there.....and so is the freight either way.!!

As your story has unfolded I'm inclined to think the problem lies not in the WUR but back in the fuel divider.
Randy, is the fuel divider the same as the damper - the round thing between the WUR and FD?  You're way ahead of me on all this, but if so then I'd agree.  Problem seems related to a recurring source of silt.  The damper might be such a source, leading to repeated reclogging.  Or it could just be defective which might do the same thing.  Maybe try bypassing it and see what happens?
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 19 May 2023, 09:44 AM
Quote from: raueda1 on 19 May 2023, 07:09 AMThe damper might be such a source, leading to repeated reclogging.  Or it could just be defective which might do the same thing.  Maybe try bypassing it and see what happens?

I thought of this.  I have tested control pressure with the gauge connected directly between the fuel distributor and the WUR, bypassing the damper, but the pressure is the same as with the damper in the circuit.

On the other hand, if the fuel divider is the fuel distributor, I have only done the following there: replaced the inlet screen and the o-rings in the pressure regulator; ensured the passages on the return side are clear.  Not sure what else I could do, but open to suggestions.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Randys01 on 19 May 2023, 07:29 PM
The fuel  damper and fuel divIder are two separate devices but our intrepid explorer has already eliminated the damper.
So now the attention turns to fuel divider..........err coff coff!

This contraption is the most exotic creation of the whole car. Now some people have had success pulling these apart and rebuilding them but I've not been one of them.

From the description of what's been done so far with the divider I'd say the problem lies in the build up of silt in the valving that reduces the system pressure to control pressure.

This is not a serviceable area with out a major pull down..........
I would not reccommend a home job on this......for me it's always a pro job becasue once it's apart there's a 100 parts.

Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: ramiro on 19 May 2023, 07:42 PM
You don't have to take the fuel distributor apart to get to the pressure regulator , you can just take the whole pressure regulation piston out with 1 screw.
The rest of the fuel distributor should not really have any effect on the control pressure , only if somebody messed the hole up out that gives pressure to the WUR.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Randys01 on 20 May 2023, 12:41 AM
The pressure regulator controls system pressure and provides a route for the returning control pressure
There is a more sophisticated valving device in the fuel distrb itself I do believe.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: raueda1 on 20 May 2023, 05:06 PM
Quote from: Randys01 on 20 May 2023, 12:41 AMThe pressure regulator controls system pressure and provides a route for the returning control pressure
There is a more sophisticated valving device in the fuel distrb itself I do believe.
Fuel Distrib = fuel divider?  If so there's lots of valving inside along with much more.  Also tiny internal filters under the tubing leading to the injectors.  They can be cleaned by pulling off the Tubing, though I doubt that's the issue.  Anyway, as far as FD goes, I strongly suggest not messing with it. I actually did manage to successfully rebuild it with help of a mentor.  However, I botched the reinstallation, caused fuel hydrolock, bent a rod and basically rebuilt the engine.  There are rebuild kits out there but far preferable to send it out to a rebuilder.  I think CIS-tech does it.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 21 May 2023, 08:59 PM
So if I connected the pressure gauge directly between two ports on the fuel distributor that normally go to and from the WUR, but bypassed the WUR and the damper, would that tell me if something in the FD was causing excessive back pressure?

I have to admit that I'm not much inclined to send the FD out to be rebuilt. It looks like that could cost more than I have in the whole car.

 
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Randys01 on 22 May 2023, 03:13 AM
As a top rail mechanic said to me one day....  "CIS?...err that's a black science".

Yes..before the FD goes in for ohaul, I'd want to be sure all the ancillary equipment is playing ball.

Let's determine if there is any silt in the FD..

I'd be inclined to run the fuel volume test./fuel pressure test again. Let it pump thru into a clear vessel for as  long as you can.
Is there any hint of residue/silt/grunge in the fuel?

Is there a fine mesh filter in the fuel delivery line where it screws into the FD. or has this been removed?
Any anything caught  here?

Remove 2 fuel injector  lines and see if there are any filters in the top of the FD....carefully prise them out  if fitted] and see  if you can peer into the top of the FD and see any muck.
Gently push down on the air flap and see if any stuff comes out .

Remove and inspect the pressure regulator. Since it was last out is there any apparent signs of grunge?.

All clear? Then we have a known quantiy.No new grunge floating  BUT have not eliminated the possibility of some being stuck from a previous era.
I will have some more advice tomorrow....have to  a bit of research: but do what has to be done to answer the above questions b4going any further.


If all clear, then it safe to say there is no longer a threat of grunge going thru the system BUT it does not eliminate the possibilty of some being stuck form an earlier era.
If you get all clear on these tests,
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: ramiro on 22 May 2023, 11:48 AM
Quote from: Feather535 on 21 May 2023, 08:59 PMSo if I connected the pressure gauge directly between two ports on the fuel distributor that normally go to and from the WUR, but bypassed the WUR and the damper, would that tell me if something in the FD was causing excessive back pressure?

Thay you control pressure should definitly be close to 0 if not you have problem with pressure regulator (it also closes the return from the WUR when the pump is off) or return to the tank.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 22 May 2023, 10:01 PM
Confirmed that pseudo-control pressure is zero without the WUR installed.  I think this indicates that excessive control pressure is originating in the WUR.

I also did the series of tests Randys01 suggested and didn't see silt in a sample of fuel from the pump, the inlet screen on the fuel distributor, or the tiny screens under the lines going to the injectors. 
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Randys01 on 23 May 2023, 04:28 AM
ok..we'll take it that grunge is no longer a problem altho we can't say it hasn't been and possibily caused some residual blockage. Just park that thought.

I don't know what kind of fuel pressure test kit you have but I assume it has a flow vaLVE IN IT. I ALSO ASSUME WE HAVE IT CONNECTED SUCH THAT THE LINE FROM THE FD HAS NO VALVE IN IT......AND THE LINE FROM THE GAUGE TO THE WUR HAS THE FLOW VALVE ON THAT SIDE.
So with the flow valve shut we should have 5.2bar.

If the motor is cold and we open the valve we should have 1.3/5bar......and as we run the motor it should climb to 3.5 ... [WUR stablised]

So where do we part company?
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 23 May 2023, 10:12 PM
Quote from: Randys01 on 23 May 2023, 04:28 AMSo where do we part company?

After opening the valve. 

In the beginning the pressure was the same as system pressure: about 5.5 bar warm or cold.  Now, after disassembling and cleaning the WUR more times than I can remember, it's about 3.2 cold. 
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Randys01 on 24 May 2023, 03:40 AM
Jeez.!!!I just wrote a  >:( full page in this and it disappeared :D
OK.abridged version.11 

Partially dismantle the WUR..with the fuel cell left in the top half, run the system press test  BUT massage the valve manually. If you get a variation in the readings, then you know it wants to work but all the devices that influence it are out of whack .

Anyway let's know.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 29 May 2023, 07:26 PM
This is an interesting idea.  I tried something similar, but with the WUR assembled.  As I remember, the pressure was always the same as system pressure whatever the position of the valve.

Unfortunately, I can't repeat the experiment right now because I've sent the WUR off to be rebuilt. 

I'll report back on whether that solves the problem. 
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Randys01 on 30 May 2023, 05:49 AM
I'll be interested in their Repair notes.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 01 June 2023, 11:43 PM
So here's the conclusion of this now very long thread.

I just installed the reconditioned WUR I ordered from k-jet specialists.  The cold pressure with the engine off was 1.2 bar.  That was all I needed to know, so I started the engine and...

it runs--strongly!  I've gone for a couple of short test drives now and this 280 SE which was off the road for 10 years runs and drives surprisingly well.

After struggling with the same lean running issue for months, I've learned a few things:

1. If all the evidence points to one thing being the problem, it probably is the problem;
2. It helps to test with known good components;
3. Sometimes you just have to spend the money.

Next step is to pass California smog.  Wish me luck!
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Randys01 on 02 June 2023, 01:33 AM

Indeed......
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: raueda1 on 02 June 2023, 06:44 AM
Very true, on all points.  Sorry it all took so long.  Happy motoring!
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 02 June 2023, 08:16 PM
Quote from: raueda1 on 02 June 2023, 06:44 AMVery true, on all points.  Sorry it all took so long.  Happy motoring!

Thanks to everyone for help and good wishes. 

I'll report back on the smog test.  The entire emission system is there, so there's a reasonable chance it will pass.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Randys01 on 03 June 2023, 09:22 PM
As a matter of interest..did they detail what was wrong or was it just "Repair WUR"?

And are u happy to tell us what it cost inc freight//levies/state/VAT etc!?
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 04 June 2023, 01:19 PM
Quote from: Randys01 on 03 June 2023, 09:22 PMAs a matter of interest..did they detail what was wrong or was it just "Repair WUR"?
And are u happy to tell us what it cost inc freight//levies/state/VAT etc!?

They sent me a different reman unit they had in stock, so I don't know what was wrong with the original one.  If I asked, maybe they would tell me once the have the old one and open it up.

The total cost to me was about $296 US after returning the core.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Randys01 on 05 June 2023, 06:05 PM
about $470 Aus..........good thing we have our own tame specialist!
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: SteveDuNord on 22 June 2023, 11:24 AM
Can I ask what code your WUR is?

I've got a (euro) '77 280se and can't work out whether I have the correct unit. Some places say yes, others no.

The last 3 digits are 101.

Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Jan S on 22 June 2023, 04:48 PM
Quote from: SteveDuNord on 22 June 2023, 11:24 AMCan I ask what code your WUR is?

I've got a (euro) '77 280se and can't work out whether I have the correct unit. Some places say yes, others no.

The last 3 digits are 101.



According to my understanding the WUR 0 438 140 101 fits the later models of the 380 SE/SEL/SEC/SL (W126/W107) and 500 SE/SEL/SEC (W126) and 560 SL/SLC (W107).

Your 1977 280 SE W116 should have a WUR ending with 030 or 031 or 041 (for the weaker engine 101-105 kW) or 010 or 057 (for the more powerful engine 130-136 kW and depending on month of production in 1977). Again, this is according to my understanding.

 
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Jan S on 22 June 2023, 04:50 PM
Source is Bosch catalog year 2017.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Jan S on 22 June 2023, 05:01 PM
I believe the EURO 280 SE W116 09/1977-07/1980 shall end with 057.

Do you know the production month?
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: SteveDuNord on 22 June 2023, 05:13 PM
Quote from: Jan S on 22 June 2023, 05:01 PMI believe the EURO 280 SE W116 09/1977-07/1980 shall end with 057.

Do you know the production month?

Apologies, my WUR code is indeed 010. For some reason the reconditioning places list the 010 as belonging to the coupe but not the SE. I don't know why there's so many versions of the WUR but there you go!
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Jan S on 23 June 2023, 06:38 PM
EURO 280 SE W116: 010 is correct if your car i produced between 08/76-08/77.

Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Jan S on 23 June 2023, 07:04 PM
The information from the MB parts catalog and Bosch catalog is a bit confusing ... I must admit. 010 seems to be right ... but could also be 057. Maybe they are quite similar?

Recommend to discuss this with a specialist dealer.
Title: Re: Excessive control pressure (combines Inside the WUR and fuel cell height & CP)
Post by: Feather535 on 27 June 2023, 12:31 PM
Quote from: SteveDuNord on 22 June 2023, 11:24 AMCan I ask what code your WUR is?

I've got a (euro) '77 280se and can't work out whether I have the correct unit. Some places say yes, others no.

The last 3 digits are 101.



Mine is 031. Unique to California apparently.