Warm Running Device

[113gray]

Hello Group. My '66 230SL runs strongly warm, but in 3-4 years of ownership can sometimes be a PIA to start cold; I rarely cannot eventually get it going, but it often takes 4-6 or more attempts. It "tries" to start, gets going a bit & stalls within a few seconds. Turning the ignition on for 20-30 seconds to get a good prime w/ the fuel pump running seems to help at times, not at others. I have checked the CSV twice as suggested multiple times by the group, but can detect no leak. Yesterday & again today, I removed the air filter from the rear of the injection pump, started her cold & held my finger over the opening. Definitely NO suction generated on either test. So, I am thinking the WRD's rod is stuck in the extended position & that I should remove it, clean it up & attempt to free up the piston. I understand replacing this unit is not too expensive for later models, but for the 230SL is > $600!! Any advice from our collected wisdom would be most appreciated as I tackle this project.  -JP-  '66 230SL 5 spd Euro.

[ja17]

Hello Jim,

The WRD can be easily disassembled and cleaned. Often times the air valve piston in the housing gets stuck. Some of the latest 230SL's did have the more modern injection pump with the less expensive WRD themostat.

Here is the photo of the later version WRD dis-asssembled.

Joe Alexander
Blacklick, Ohio

Download Attachment: 20046281523_InjPumpWarmUpDeviceParts_1.jpg
9.25 KB

[Ben]

Can the early cars use some of the later parts, like can you put the housing from a late car onto an early pump and therefore use the cheaper thermostat !!

Regards,
Ben in Ireland.
'64 230SL 4sp.

[hands_aus]

The thermostat rod of the 230sl only moves a couple of MM while the later thermostat extends about 10-11 mm.

So probably they can't be swapped.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[lurtch]

Hello Jim - - The WRD on my FI pump was damaged beyond repair by corrosion. As you have found out is very difficult to obtain these units by themselves. Out of desperation I came up with a temporary fix that is on the way to  becoming  my permanent fix.
I ELIMINATED IT !  Here in California I am able to get away with this "cheap trick" because we have very mild winters. It is nothing more than a jack screw with a locknut to hold the correct warm running pump setting. For what it is worth - - Larry in CA

Download Attachment: WRD-over-ride-device.jpg
32.63 KB

[George Des]

Jim/Ben,

The early thermostat used on the 230Sl FI system is a wax filled thermostat. The housing it sits in is quite different from the newer ones used on the 250/280Sl so they are not interchangeable. I would suggest you get in touch with Hans in NY to see if he has some used  serviceable ones lying around that he would sell to you. Not much that can go wrong with these unless they were mistreated somewhere along the line. If the housimg and mechanism is short, Hans would still be the best source of what to do with this.

George Des

[113gray]

Group, to bring this thread up to date: Using the excellent advice provided here earlier, I removed the WRD air filter, started up cold (w/ the usual difficulty)& repeatedly confirmed there was no suction at the opening. I took the WRD out, disassembled & found the piston tightly stuck in the air valve body.(The earlier (1st version?) of this unit has quite a few differences from the later ones.)Then confirmed the old style thermostat still functioned in a pot of boiling water. The thermo shaft extended from its resting protrusion of 4 mm to 7mm at full boil. Cleaned up the piston, valve body & shaft, reassembled & installed & tried starting her cold. IMMEDIATE response then & every time since. Later, checked that the suction at the filter opening disappeared at full warm up & it does that also. I can't express enough appreciation to all present/past posters on this topic for their help.       Jim Pancoast '66 230SL

[66andBlue]

Hello Jim,
following your description I tested the thermostat and I am happy that the pin moves by 3 mm as you described. However, I noticed that there was no O-ring to seal in the thermostat. Did your WRD have one? Also at the base of the thermostat there was glue-like material, could that be an old seal ring? I am attaching a picture which I hope will show what I mean.
On the SLS web site it shows the 230 SL thermostat parts but it is not clear to me whether this O-ring goes beween the housing (the one through which water circulates) and the thermostat base or between the stem and the lower valve body. Does anybody else know?

Alfred
1966 blue 230SL automatic

[Naj ✝︎]

Hello, Alfred,

I believe no 'O' ring is used to seal. I used some ptfe tape around the thermostat base.
Item # 69 on the SLS picture is a copper ring - I believe its there to adjust to air flow during warm-up. I remember playing with it to get a decent idle speed from a cold start.

naj

68 280SL

[66andBlue]

I had forgotten that I had ordered this copper O-ring (part number: N007603 020101) from the local Mercedes dealer and when it finally arrived I wanted to find out where it goes.
Both  Hans at H&R and Gus at Pacific Fuel Injection assured me that it goes between the coolant housing and the base of the thermostat as shown in the picture. But only the older style thermostat requires the ring, the later shorter version does not.
In addition to the copper crush ring they also use some Permatex for sealing.
Download Attachment: IP_Thermostat_SealRing.jpg
41.19 KB

Alfred
1966 blue 230SL automatic

[bpossel]

I replaced my small thermostat in the IP pump this weekend.  New one (for my later pump) was under 25 bucks (which included shipping)

Anyway, I clamped off the 2 hoses and then removed them so that I could easily remove the small housing which holds the thermostat.

I was surprised that when I went to re-connect the 2 hoses that there was little to no radiator fluid in the hoses...?

 :oops: Is this normal?  Are the hoses only filled with fluid when the engine is running?

Thanks for clarifying...

ps. replaced my thermostat because I have a similar issue as Jim.  Car starts with right up when warm, barely turn the key and it fires right up!  However takes 6-10 cranks to start when cold.




bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[Ricardo]

Bob
I found the same thing with fluid levels and I believe this is normal. When I re-fill the system, I disconnect the top hose at the IP thermostat and fill until coolant starts to dribble out the hose. It's the highest point in the system and I figure this helps to bleed out any air. I don't have to add any more coolant to the reservoir, so I assume this is the correct amount and that there is always a little air at the top of the system.
After changing my thermo twice, the car still starts as you have described.

[glennard]

Turning the Ignition Switch to 'Start' in cold weather energizes the stater solenoid(thereby powering the starter), the cold start solenoid(squirting fuel pump gas into the common intake manifold), and energizes the solenoid on the FI pump(throwing the FI rack to rich-rotating the pump pistons).  Hold your hand on these 2 solenoids to see if they click while someone 'starts'.  Another way to get gas into the engine is to put 12 volts on the CSV via a switch in the cabin while simultaneously (or 1 or so seconds before) 'Start'ing.

The FI solenoid action(rack movement) can be seen on a 5mm(4mm ?) bolt screwed into the end of the rack(behind the cap on the front of the FI pump).

Happy cold starting!!

[Shvegel]

In case anyone else is looking for the cause of their problem I had the little air filter come apart and the plate at the top of the filter was acting like a check valve and occasionally blocking the flow of air to the engine so I had an intermittant idle issue.

The lessson is before you adjust or shim anything remove your filter and try it. A dirty or bad filter can cause alot of headaches.

[hands_aus]

I have added
'oil/lubricate WRD'  and
'change injection pump oil'  and
' lubricate distributor shaft'
as part of my regular maintenance every 6 months.... I don't travel too many KMs in my weekend car.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[glenn]

Re: The WRD.   affectionately dubbed the Willnot Run Device.
  A few thoughts on the recent rehab of three Willnot Run Devices.  First, the WRM does two things.  It opens and closes an air control valve admitting air into the vacuum of the intake manifold and it affects the fuel flow regulation in the injection pump.  It does this in response by a heat feeler (in the radiator coolant flow) to the coolant temperature.  The air valve is full open at low temp and full closed at high temp.  The fuel is likewise affected.
       But, if it is not working properly, you've got trouble.  If it is frozen open(the most likely), you have a 10 mm diameter vacuum leak.  This is many times the idle air flow.   Therefore, there is no way ever to get a correct idle via the idle fuel screw and the idle air screw with a 10 mm vacuum leak.      
       So, you gotta take it apart.  (Remembering and noting the positions of all parts)  Disconnect and plug the two coolant lines.  Disconnect the vacuum line.  Unscrew(impact tool) the two screws holding the heat feeler.  The heat feeler should come loose, hopefully.  Unscrew(impact tool) the two screws holding the control valve housing.   The control valve(piston) is probably at the top of the cylinder.  Spray some PB Blaster on it.  Tap it gently downward with a wood dowel.   The piston will go down and the guide pin will extend further out the bottom.  Put the housing in a vise(cardboard on face) and gently force the piston back up the cylinder from the pressure on the guide pin.  Repeat taping and pressing until piston can be pulled out the top.  Remove the guide pin with its captive spring.   Make sure the guide pin moves up and down its cylinder against the spring force.  
       Clean and lubricate everything and make sure all move easily.   Reassemble(with a little anti-seize lube on screws).   Seal heat feeler to heat feeler housing.   Make sure the heat feeler screws are tightened to get even spacing between faces.   Some washer and spacers may be necessary to get correct responses.  The air valve should be open with cold coolant and closed with hot coolant.  See your manual for the temp it closes at.  Unscrew the air filter to check open and closed.  With cold coolant it sucks air like crazy.  With hot coolant it is closed.  With the heat feeler housing attached to the control valve housing you can dip the heat feeler in boiling water and observe the pin extend out the bottom.  Put  the hose back on the air/vacuum side and blow-no flow should result.  Reinstall on the pump with the oval washers.  Now you can do a correct idle fuel/idle air adjustment at engine operating temp conditions.  
        A few observations.  1.  None of the three coolant flows were the same.  The coolant came from the head thru the heat feeler and out.  Then it went to 1, the venturi housing, 2, to pipe around the venturi housing, 3, back to the water pump.  The heat feeler housings were cloggled and nipple eroded.  The heat feeler would not come out.
              2.  The control valves were frozen from soot(blow back) or dirt.
              3.  The guide pin/spring were frozen.  The captive piston/spring on the pin must slide freely to open/close
                 the valve.
              4.  Needed an impact tool to loosen screw blade heads.
              5.  Control valve housings were different.
              6.  Heat feelers were different.
              7.  One WRM was designed with a 'turn off' knob in the control valve housing.   Shows MB's confidence in their   engine fuel management system.
              8.  The pin on the later WRD moves about 10 mm.  At -25 degrees C in the Schwartz Wald the pin is fully withdrawn and the temperature compensation is 100% of range inside the pump.   As the coolant heats to 75 degrees C(or so) the pin extends out the 10 mm(or so) closing the WRM air valve and reducing the temperature compensation to 0% of range.
         So, it is another example of  'No two identical Mercedes were ever built'.  

        Most important---  Correct 'Idle adjustment' cannot be done if the WRD is frozen open (and you've got a massive vacuum leak).              
           (If this is redundant to everybody............)      

[glenn]

hands aus,  What lubricant for the control valve in the WRD??

[hands_aus]

I use a couple of drops of engine oil and make sure there valve moves freely before re-assembly.

[Eminent]

The air valve is full open at low temp and full closed at high temp.

"Full closed at high temp",  thats what i want to know. Even at 175F there is suction at my WRD. Not as much as when the engine is cold, but there is.
Gonna clean the whole thing and see if i can do something with the shims to work it properly.
Thanks.

[stickandrudderman]

Soemtimes there is sufficient wear of the piston/bore so as to cause a bleed. A liberal coating of copper slip will stop it, although in practical terms a small bleed can be countered with the idle air adjustment screw.

[Eminent]

Checked the movement of the pin today. Only about 4mm movement when dipping the thermostaat in hot water.
Something real different as the 10mm in Glenn's answer.

[66andBlue]

4mm is very good for the WRD in a 230SL FIP but probably not enough for the later style thermostats.
See replies #3 and #7.
Which one do you have or did you test?

[glenn]

Hi, Just guessing, but the thermal element was designed to operate from, say,  minus 25 degrees F to 180 F or so.   Was 4 mm from 80 to 180?  About right then. ..  And they fail with age??

The WRD and air/fuel ratio at temperature is   .

Try the 'Lurtch' override.  

Also, 2 things must occur at operating engine temp(180 ?)-   1. the air valve must be shut and 2. the FIP WRD lever must be pushed to full travel.