WRD Disassembly Question

[Worldflier]

Good day,

I’ll start today by admitting I am a newbie to both these cars and the forums (tho I owned and extensively wrenched on a carbureted W108), so I apologize ahead of time if I step on any toes. I also was unable to figure out how to add my question to previous discussions on the WRD.

I have been able to remove the WRD from the car and am trying to figure out how to remove the stuck plunger from the housing.

It appears that the little black pin needs to be removed, and then somehow to back out the silver pin holding the top of the plunger. Does anyone know how this is held in? A discussion with a mechanic lead to the idea it may have had a nut that is broken off. Any help is greatly appreciated. Pics to follow.
Thanks! Dre

[Benz Dr.]

Don't worry too much about removing the slide valve. Use some penetrant to free it up by moving it up and down in its bore. I use a bit of brake grease to lube the valve before assembly. Use sealer under the thermostat to prevent leaking.

[stickandrudderman]

See if you can find someone with an ultrasonic bath and clean it in that. Should come up like new and free up the seized piston too.

[ja17]

Yes the nut, or end of the bolt is broke off. It is for test purposes only and does not have to be removed as long as it is in the "up" position. The roll pin holds the bolt from coming out, but the bolt normally rotates when the nut is turned. Try some heat also to free up the slide valve (heat gun) with penetrating oil.  A heated ultrasonic cleaner is also a good option.

[Worldflier]

Thank you for the suggestions!

Does anyone have a photo of a “healthy” slide valve, but and roll pin, so I can see how it is supposed to look? I’m not sure I’m following the descriptions. 🤔

Dre

[heinsbush]

Hi All,

I'm having the same issue as Worldflier. It seems my piston is stuck (I assume if I push or pull on the black nut, the piston should move up or down!?)

I'm pulling and pushing like crazy, but there is zero movement.
Do I now try to remove (unscrew) the black nut? or the silver nut that sits underneath?

FYI - I can push in the plunger that is coming out on the bottom, but I'm just pushing against a spring, there is no movement on top...

Sorry Worldflier for writing in your post, but I assume you have the same / similar questions...

Thanks
Heinz

[Worldflier]

No worries! I figure the more the merrier.
As suggested, I have ordered a heated, ultrasonic cleaning tank which should arrive this Thursday. I’ll let you know if it works!

[heinsbush]

Well hope the cleaning will work.

I finally got mine „moving“ again with sufficient force and WD40... cleaned it, adjusted it, tested it.

It closes the airflow nicely when getting hot.

I mounted it in the car but it actually runs worse than before. It idles well, but split linkage test indicates  way too rich mixture. Engine RPM increases nicely and significantly with more air... but it doesn’t really react to more fuel... maybe something else is stuck inside the injection pump...

[mrfatboy]

How many rpms does the engine increase by when adding more air during the split linkage test?


With everything setup correctly and doing the split linkage test:

Adding  air should increase rpms slightly(~50rpms) then engine should stumble and die.

Adding fuel engine should immediately stumble and die. 

Make sure your linkages are correct by following JA17’s linkage tutorial.

Check the CSV for leaks.

Adjust the idle CO when engine is hot using the thumbscrew on back of FIp. Make sure engine is off when doing adjustments.   Do a search for adjusting CO and/or idle mixture. it has been discussed many times with lots of detailed info. 👍

[heinsbush]

Thanks for the relay!
It increases by a lot, I can rev it by several thousand RPMs... I didn’t look at the exact RPM but there didn’t seem an end to high it would rev...

I found CSV leaking and fuel smell in oil. Will try to fix CSV as next step and then adjust on the screws...

Could there also be something stuck on the Fuel Injection Pump?

Thanks!

[Worldflier]

Good day! Cleaning my WRD will be my first time working with an ultrasonic cleaner. Any advice about which solution to use? I also take it I will not be cleaning/touching the thermostat, which seemed to operate ok during my test.
The cleaner arrives tomorrow, and I’m excited to see it work!
Thanks! Dre

[bracurrie]

Thanks for the relay!
It increases by a lot, I can rev it by several thousand RPMs... I didn’t look at the exact RPM but there didn’t seem an end to high it would rev...

I found CSV leaking and fuel smell in oil. Will try to fix CSV as next step and then adjust on the screws...

Could there also be something stuck on the Fuel Injection Pump?

Thanks!

Based on what I have learned from others here and not on my experience or training I would offer the following observations: Fuel in oil is sure sign of too rich. These FIPs seem to fail in a way that results in over rich mixture. Oil change needed soon. Then check injectors for leakage, then try to set idle mixture. If then it is still too rich you may have FIP problems that will need to be addressed by someone with a Bosch machine, parts and experience to clean and possibly rebuild the pump with calibration. 

[Worldflier]

Good day!

I finally had a moment to clean and then disassemble my WRD.

The piston seems to be ok, and putting it in the bore with some grease, it moves pretty freely and will cut off the air to the vacuum side of the system. That much is good and understood.

Where I’m not sure is:
1. The little pin (apparently with the screw broken off) can go right through its hole into the bore. There’s a tiny roll pin to keep it from falling out, but what is supposed to keep it from falling in?

Additionally, since the pin is offset, it seems to be designed as a way to adjust the WRD piston height. Is this true? Wouldn’t the height just be set by the set screw on top of the WRD piston contacting the thermostat pin?

2. What pushes the WRD piston up? Is that pressure coming from the fuel adjustment on the injection pump? I initially thought it would be from the spring under the piston, but there’s play in that system, which would make it inaccurate, and the piston moves fully up and down before the spring contacts the bottom of the housing.

3. How to set/adjust the WRD. Do any of you have step-by-step instructions on how to do this? Is it in a manual somewhere?
This one is of t he earlier type, so full air/fuel increase to 0 should happen in just a few mm thermostat movement. This leads me to suspect the thermostat pin and piston adjusting screws would have to be in contact with one another to insure 0 play, but at what temperature?

Sorry this is such a long set of questions. Any help is greatly appreciated, as would be an image of a healthy (aka unbroken) offset pin.
Many thanks!
Dre

[Worldflier]

Good day,

Something else comes to mind:
I see shims mentioned in pretty much every other post on the WRD. Mine doesn’t have any. Instead, it has an adjusting screw atop the air valve (what I have been referring to as the piston), and nothing at the bottom pin, which adjusts the mixture during high idle.
Do any of you have a link to where to buy some, in case I need them during tuning?

Speaking of tuning, to add/remove shims, the thermostat will need to be removed repeatedly. Won’t this allow coolant into the air valve housing? Isn’t it under pressure when warm, necessitating a sealant like RTV, who’s bond will be compromised with every removal? What am I missing?