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Discussion Starter #1
Hey all

Here's my attempt at documenting the Warm Up Regulator Rebuild. From what I can tell, this is not a common repair. Most times this part is replaced. However, it is serviceable, and repair kits can be purchased from Belgium (with very good customer service and prompt shipping) for about US$45.

This is the site to purchase WUR rebuild kits. This company also produced fuel distributor rebuild kits for many Bosch models. Know your part number.

My WUR ends in 068, and therefore utilizes rebuild kit #5.

Ferrari 400 - K en KE Jetronic rebuild kits

This company also offers an adjustable bolt for the bi-metal strip, which I did not order. My feeling is that the failure with my WUR has to do with a deteriorated o-ring under the diaphragm and possibly a clogged fuel screen at the outlet fuel line. Will see...

A very grungy looking WUR


Cleaned up a little and removed from the car. Removal is easy: detach the fuel lines, detach the vacuum lines, and unscrew the 2 bolts holding the WUR onto the engine. These bolts are removed with an Alan wrench, IIRC 5mm.


The WUR comes apart in 2 halves once the four brass screws are removed from each corner. I also removed the nuts, which were stuck in the openings, using a punch. From what I can tell, the bottom half of the WUR is sealed and not serviceable. There is another plunger in this area.

NOTE: my WUR has 2 springs under the bi-metal strip. Most others I have seen only use one. This may provide additional control pressure to the plunger. I'm not sure.

Removal of the fuel inlet/outlet


Close-up of the back side of the bi-metal strip and corresponding resistor. Note the resistance is stated at 20 Ohm +/- 5%. I measured mine to be 25 Ohm, within the tolerances, but they can range from 18-30.


Here's a look inside the WUR. My next step is to remove the 4 brass screws that hold the diaphragm to the body. They are stuck on, so I soaked them in Kroil. Will try again. Hoping I won't have to back them out with a tap.
The bolt on the bottom of the picture is the one that can be adapted to an adjustable "knob" via the link above.


Finally for today, a link of all of the parts that were delivered, agains the old ones.


Also, Here is a detailed link on how to calibrate the control pressure in the WUR, however, my feeling is that a new o-ring will compensate for any lost pressure, over and above any additional adjustments.
http://www.benzworld.org/forums/w126-s-se-sec-sel-sd/1372083-warm-up-regulator-wur-calibration.html

More to come once the diaphragm is off the WUR body....
 

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Discussion Starter #3
UPDATE

Finished taking the WUR apart, and put it back together.
Replaced the o-ring. I couldn't get to the screen, but cleaned it thoroughly with carb cleaner and it is flowing freely. Replaced the copper washers at the inlet and outlet. Reinstalled all the components, and added a new dab of multi-purpose grease to each end of the pin that drives the diaphragm to hold it in place.

The Kroil was able to free up the four screws holding the diaphragm together. I then used a small screw bit and the impact drill to coax them out. The surface shown is supposed to be smooth, and it was to the touch. The original o-ring looked to be thinner, and showed some cracking. New one fit right in.


Here's a picture of the diaphragm cap and "button", DO NOT LOSE THE BUTTON


Reinstalling each disc. The diaphragm is the thin shiny piece of metal under the cap.


Putting it all back together. New rubber seal in place.


Placement of the spring/pin mechanism is very important. I decided to line everything up from the bottom. The pin actually stuck to the diaphragm "button" with grease and then lined up perfectly in its seat. Bolted down the brass screws with even pressure, and it was done.


NOW, did it work? Well, not really. The car works the same as before. From a cold start, hit the gas and ... BOG ... Let off the gas an it idles fine again. Once warm, it revs and moves just like it should.

SO...my theories are as follows:
1) The WUR is still bad and needs to be replaced. Meaning this was a $40 lesson.

2) The WUR is working fine and there's not enough control pressure coming from the fuel distributor to overcome the pressure across the WUR diaphragm spring. So when the engine is cold, hitting the pedal causes the car to run too lean and stall. When the WUR warms up, the spring bends, allowing the diaphragm to open and full control pressure can flow through the system. Once the initial control pressure is increased, I can then adjust the idle down to compensate for the increased fuel in the mixture at start up.

2a) Mini-theory: There's a vacuum pressure issue somewhere else and I will never find it short of rebuilding the whole system.


DOES ANYONE HAVE ANY OTHER IDEAS!!???
 

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1981 380SL
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Buy/construct a set of K-Jet pressure gauges and do a proper diagnosis. No need for theories or new parts to replace old parts that are still good.
 

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Discussion Starter #5
Buy/construct a set of K-Jet pressure gauges and do a proper diagnosis. No need for theories or new parts to replace old parts that are still good.
Although that might seem like the most logical approach, I have no idea how to do that. I guess I can learn through YouTube. I have a pressure tester, just never used it. Not sure if all the fittings will work.

Hmmm...
 

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Always Remembered RIP
1979 280sl 4 sp w/ac 1957 MGA 1998 volvo xc/70 2004 F150
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I believe it's a documented in the egv-107 sticky.
 

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1981 380SL
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Job 07.3-120 in the Field Service Manual (link in EGV107). Simple procedure.

There's probably stuff on the net for building a set of gauges. I went ahead and bought a professional set. Came with nice instructions and a case. Cost about $100 IIRC.
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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I believe it's a documented in the egv-107 sticky.
It is. I recently reviewed it as I have never done it on a CIS either.
Going to start on the 500 as the WUR is easier to get to than the 280.

Thanks for the write up on the WUR baco. Disappointing it did not help.
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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29,492 Posts
Do you disconnect WUR from top or below?
I find it easiest from underneath. Remove the oil filter can and it's staring at you in the face.

From the top, it's hard to get two hands in there while your back starts to spasm friom being bent over.

careful removing the fuel line as the adapter to the WUR likes to unscrew at the same time.

Thus the need for two hands for two wrenches.
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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1985 280SL
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UPDATE

Finished taking the WUR apart, and put it back together.
Replaced the o-ring. I couldn't get to the screen, but cleaned it thoroughly with carb cleaner and it is flowing freely. Replaced the copper washers at the inlet and outlet. Reinstalled all the components, and added a new dab of multi-purpose grease to each end of the pin that drives the diaphragm to hold it in place.

The Kroil was able to free up the four screws holding the diaphragm together. I then used a small screw bit and the impact drill to coax them out. The surface shown is supposed to be smooth, and it was to the touch. The original o-ring looked to be thinner, and showed some cracking. New one fit right in.


Here's a picture of the diaphragm cap and "button", DO NOT LOSE THE BUTTON


Reinstalling each disc. The diaphragm is the thin shiny piece of metal under the cap.


Putting it all back together. New rubber seal in place.


Placement of the spring/pin mechanism is very important. I decided to line everything up from the bottom. The pin actually stuck to the diaphragm "button" with grease and then lined up perfectly in its seat. Bolted down the brass screws with even pressure, and it was done.


NOW, did it work? Well, not really. The car works the same as before. From a cold start, hit the gas and ... BOG ... Let off the gas an it idles fine again. Once warm, it revs and moves just like it should.

SO...my theories are as follows:
1) The WUR is still bad and needs to be replaced. Meaning this was a $40 lesson.

2) The WUR is working fine and there's not enough control pressure coming from the fuel distributor to overcome the pressure across the WUR diaphragm spring. So when the engine is cold, hitting the pedal causes the car to run too lean and stall. When the WUR warms up, the spring bends, allowing the diaphragm to open and full control pressure can flow through the system. Once the initial control pressure is increased, I can then adjust the idle down to compensate for the increased fuel in the mixture at start up.

2a) Mini-theory: There's a vacuum pressure issue somewhere else and I will never find it short of rebuilding the whole system.


DOES ANYONE HAVE ANY OTHER IDEAS!!???
Follow up on old thread. Were you able to reolve your problem of "From a cold start, hit the gas and ... BOG ... Let off the gas an it idles fine again. Once warm, it revs and moves just like it should."? My 280 does exactly the same thing. I was about to pull my WUR and try to clean the screen until I saw this post. Any news or other suggestions to the problem?
 

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Discussion Starter #14
Yes, I was able to solve the bogging problem once started, but then the car wouldn't start at all from cold, so I got fed up and sold it.
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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No offense, but perhaps the thread title should be re-worded.
 

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1985 280SL
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Yes, I was able to solve the bogging problem once started, but then the car wouldn't start at all from cold, so I got fed up and sold it.
Baco99, Sorry to hear you couldn't solve the WUR problem, if that is what it was. I was hoping for a solution. Mine starts great and after about 2 or 3 minutes of warm up, runs great. But during that 2 or 3 minutes it seems lean, like needing to be choked. Now I'm a little concerned about screwing things up trying to solve my problem.
 

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Discussion Starter #17
I don't think the final issue was the WUR. The WUR repair worked fine for about 2 months, then a new issue arose and the car wouldn't start at all. It wasn't getting any gas at start up. I attributed it to the cold start valve in the manifold. I had some fun with the car while I had it, but I doubt I'd get another R107. Too many complex systems for an amateur spanner spinner. I lost almost 2 grand when I sold it.

Wish I had my '67 200D back.
 

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1982 300SD, 1984 380SL, 1997 E320, 2008 R350
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I had that problem with my 380SL. Resolved it by replacing the clogged fuel tank strainer, new fuel pump, accumulator and filter. You can actually hear the increase in the noise level of the pump as it gets progressively clogged, until it just seizes. Even the fuel level inside the tank will cause the pump to run louder when the fuel level approaches 1/4 tank. There is a reason why those pumps are so cheap nowadays. The "good" $100-dollar pump from AutohausAZ lasts two years max.
 

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1986 560SL with M120 V12 Engine, 1988 560SL Stock
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I had that problem with my 380SL. Resolved it by replacing the clogged fuel tank strainer, new fuel pump, accumulator and filter. You can actually hear the increase in the noise level of the pump as it gets progressively clogged, until it just seizes. Even the fuel level inside the tank will cause the pump to run louder when the fuel level approaches 1/4 tank. There is a reason why those pumps are so cheap nowadays. The "good" $100-dollar pump from AutohausAZ lasts two years max.
Hmm

Samsons pump is 10 years old (but it is a 129 pump). Delilahs pumps are 14+ years old, more likely 30 years old.
 
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