Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: dseretakis on August 05, 2008, 13:10:44
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Hi all. I'm tackling the WRD on my 1971 280SL which I have not been able to get running now for a long time. See "non-running 280SL" thread for those who are not already familiar. Anyway, I removed the WRD and all looked OK. The plunger moves freely. I immersed the thermostat in boiling water and the rod traveled by 6mm. However, when I removed it from the water and let it cool down for 2 hours it had not resumed its original position. I then pushed the rod back and it insisted on returning to the hot "extended position" Am I missing something here or is it just defective?
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The thermostat for the 280SL's is not that expensive to replace. It is the one for the 230SL's that will cost you an arm and a leg. :D
I would expect at the very least for that pin to return to it's original position once cooled down.
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hans at H&R can fix the WRD on the 230 sl's
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I ordered a new one from www.buymbparts.com. It was $60. The local dealership wanted $113.
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Hello deseretakis,
Your starting problem lies elsewhere. It sound like your IP thermostat is ok. Once it extends it will resist moving back. It depends on the spring located in the WRD to push it back after installation.
Remember, if you have air, fuel, spark on time and compression it will run. A fresh set of spark plugs is an inexpensive investment. You can always re-use the removed ones if they are still good. Check the compression while you have the plugs out. If the timing chain has jumped it will show up in your compression readings.
Squirting a bit of starting fluid or hot wiring the intake cold start valve will get fuel into the engine. If fuel will not get it running, check for spark by removing a plug wire and hooking up a loose spark plug to it. Ground it to any point on the engine while someone cranks the starter. You should see spark. If you have spark, it must be on time. Remove the distributor cap and make sure the rotor is pointing to the #1 cylinder when the engine is at TDC #1 compression stroke.
Let us know what you find.
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I also believe that the problem lies elsewhere, but where? I have spark, the engine starts and runs smoothly now that I changed to non-resistor plugs. It will however not continue to run without continuously applied throttle and it puts out much gray/tan smoke. Compression is uniformly good across all cylinders, cold start valve works well, inside of tank is bright and shiny.
Dimitri
quote:
Originally posted by ja17
Hello deseretakis,
Your starting problem lies elsewhere. It sound like your IP thermostat is ok. Once it extends it will resist moving back. It depends on the spring located in the WRD to push it back after installation.
Remember, if you have air, fuel, spark on time and compression it will run. A fresh set of spark plugs is an inexpensive investment. You can always re-use the removed ones if they are still good. Check the compression while you have the plugs out. If the timing chain has jumped it will show up in your compression readings.
Squirting a bit of starting fluid or hot wiring the intake cold start valve will get fuel into the engine. If fuel will not get it running, check for spark by removing a plug wire and hooking up a loose spark plug to it. Ground it to any point on the engine while someone cranks the starter. You should see spark. If you have spark, it must be on time. Remove the distributor cap and make sure the rotor is pointing to the #1 cylinder when the engine is at TDC #1 compression stroke.
Let us know what you find.
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Joe, upon reading your post more closely it seems that the spring action in the WRD should push against the thermostat thrust rod. While the plunger in my WRD moves back and forth freely, there is no spring action. I can push and pull on the plunger but it is not spring loaded. It is almost as if the spring is missing. I want to take it apart but there is a flange on top of the air valve housing that holds the air valve/plunger/spring in place. The flange appears to be pressed in place. How do I remove it?
Dimitri
quote:
Originally posted by ja17
Hello deseretakis,
It sound like your IP thermostat is ok. Once it extends it will resist moving back. It depends on the spring located in the WRD to push it back after installation.
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Hello,
The spring action comes from within the IP itself. You will feel it push back at the IP thermostat when you are re-installing it .
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Thanks, that clarifies it for me. I wasn't too excited about disassembling it further.
Dimitri
quote:
Originally posted by ja17
Hello,
The spring action comes from within the IP itself. You will feel it push back at the IP thermostat when you are re-installing it .
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I'm pretty much at the end of a total engine restore, and I have a question on the warm running device thermostat.
It's a 250 with the late warn running thermostat device type.
I have two questions.
First of all does there need to be a copper or rubber ring between the thermostat and the housing (at approximately the tip of the pen If you look at the picture I have attached). Does it really hold the water out without a sealing of some sort?
Secondly, how far on the thread does the 2 nuts needs to sit? At least as I understand it the postion of these two nuts is equivalent to adjusting the device by adding or removing shims. Is this correctly understood?
As always 250 times thanks!!
Ulrik
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Hello Dimitri,
Sounds like the rack in the injection pump is stuck. If this is the case the spring action under the heat feeler is canceled out. This will also cause the symptoms you descrbe. Check the rack for movement. There is an opening on the front end of the IP where you can check the rack movement with a screw. If you need more guidance to find it let us know.
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Hello Ulrik,
The two nuts on the heat feeler are factory set and not usually changed. In fact with the latest version of the heat feeler, the setting is not adjustable. Changing the adjustment does change fuel mixture at cold idle and everthing else also! It also changes how soon the cold start air supply shuts down. So this is not something that is usually tampered with. Adjusting the length of the heat feeler will change fuel mixture all speed ranges, and will change the shut of temperature of cold air supply.
Oval shim change, barometric compensator shim change, or rack adjustment will change fuel mixture at all speed ranges and temperatures. I like to do the oval shims since it is easy and things are easily put back to the way they were if needed. A rack adjustment is preferred by some but more work and more difficult to put back.
Idle thumbscrew change will change idle fuel mixture only.
Internal centrifugal governor paired screw adjustments, adjust mid and high speed range fuel mixture. Lots of work and normally not for the amateur.
Make sure linkages are correct, basic engine tuning is good, and fuel volume and pressure are correct or you will be wasting your time.
What are your issues at this time?
Yes there is no additional seal at the connection of the WRD heat feeler and the special tapered spacer. It is a compression seal.
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Thanks Joe!!
OK I guess it was stupid of me to play with those two nuts then!!! I seem to remember that they were ~2/3 to 3/4 towards the end of the pin when I removed it, but I don't remember exactly. When I read on the forum about this WRD nobody ever mentioned these nuts, all the talk here was about the shims, so I didn't know the implications of playing with it. Well don't play with things you don't understand I guess is the lesson...
Well then, can you or anybody else measure the distance from the end of the tip to the nut (and maybe also the distance from the other side for quality control...). That at least will give me a starting point. Knowing how sensitive it is since a single shim can alter things a great deal, I guess I can expect some time fine tuning this thing....
I really do not have that many other issues, everything has been running pretty smoothly uptil now, so I'm optimistic and confident...
Best wishes,
Ulrik
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Hi Mulrik,
You're chasing a problem that bugged me for a long time. I had the same WRD thermostat as you with the adjusting nuts. I think it was a much better system than the shims, but there is no longer a choice. It sounds as if your's is still working, so you can do with the nuts, the same as the rest of us do with the shims: trial and error. You can write down the amount or turn you give the adjustment nuts and see what happens. If the mixture is worse, go back. If it's better but not good enough, go forward. Just keep notes on which way you adjust and what happens. If you suspect it may be weak, get a new one and a few shims. To adjust the mixture with shims; add or remove them.
Be aware that the seat washer that the thermostat sits in may need to be drilled out to 13mm to accommodate the newer thermostat because the bottom from where the rod protrudes is different. Good luck.
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Just for reference, the thermostat is part number 001 203 95 75. MB USA list $100 (whoever was quoted $113 was being ripped off), my price $73.83 from Mercedes. However, you can get one from AutoHAusAZ.com made by the original vendor (Behr) for $19.18.
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Joe Alexander wrote earlier in this post that "Oval shim change, barometric compensator shim change, or rack adjustment will change fuel mixture at all speed ranges and temperatures."
So let me try to understand this. If you add shims under the WRD (or adjust the two nuts) this will change the fuel mixture at all RPM ranges, that is if the engine is cold. I understand that much!!
So here's my question. If you adjust the WRD (shims or nuts) will it also affect the fuel mixture when the engine is warm? If so please explain. In my view the WRD shuts of completely when warm and that's the business of it, but does it also affects fuel mixture when warm?
The reason for asking is that I have just started my engine after a complete rebuild (which included playing with the WRD...), and now I'm in the proces of making it run nicely.
As always, thanks,
Ulrik
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Hello Ulrik,
Here is my take on the WRD....
First of all with all adjustments of the IP system, the engine must be in good tune, with a clean fuel supply with proper volume and pressure. Engine linkages should be set correctly. A leak free intake starting solenoid is important. The engine should have no vacuum leaks. The small round air filter on the injection pump WRD should be checked to make sure it is not clogged. The WRD heat feeler should be functioning correctly.
The WRD is designed to change the fuel and air supply to the engine during the warm up period when additional fuel and air is required. The WRD perform the same purpose that a manual or automatic choke preforms on a carbureted engine. The rate of this mixture change in the WRD, is constant and not adjustable being that it is regulated by the heat feeler which is constant. The temperature that the extra air supply is closed off is set by the Bosch factory when the pumps are being manufactured. This closing of the air passage is accomplished by the addition or subtraction of the small round washers or the two adjuster nuts (earlier heat feelers).
Any change in the length of the " rod" from the WRD, extending down into the IP, will change the main rack position and consequently the fuel mixture. Changes in the quantity of oval shims, small round heat feeler shims, or the two adjustment nuts (early heat feelers) will change the length of this WRD "rod" and consequently the fuel mixture by moving the main rack in the IP. Here again, rate of change is constant depending on engine coolant temperature and the heat feeler.
Removing or adding of any oval shims will change the mixture of the IP at all speed ranges. It will not alter any function of the WRD. Removing or adding small round shims or the changing the adjustment nuts on early units, will also change the fuel mixture in all speed ranges. In addition adding or subtracting any small round shims will change the function of the WRD (the temperature that the extra cold air supply is shut off).
These WRD units are factory set and are not a normally meant to be tampered with. The adjustment that can be made is the actual temperature at which the extra air passage is closed off. This accomplished by changing the small round shims. Remember any changing of the small round shims also changes the length of the WRD "rod" and thus the IP mixture at all speed ranges.
You can add shims one place and subtract at another to keep mixture the same and theoretically accomplish a change in the shut down temperature of the air passage without changing the mixture.
Engines and IPs wear with age, things change and engines are different. Certain adjustments compensate for wear and differences in engines. You can remove small round shims and add the same thickness large oval shims to make the extra air supply stay open a little longer ( later temperature) to create a "leaner " cold running mixture, but you are deviating from the factory settings. I suspect the range of adjustment in this process is quite small before the WRD air supply fails to shut off completely.
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Here is my understanding of the WRD adjustments.
The top round washers are used to adjust timing of the heat feeler impact on the fip. Fewer washers means the heat feeler will impact the rack earlier. More round washers means the heat feeler will impact the rack later. Example: Let's say the heat feeler fully extends in 180 seconds. If you move the feeler closer to the rack by removing washers it will effect a change earlier. If you move the heat feeler farther away from the rack adjuster it will effect a change later in the heat cycle.
The lower oval washers act differently. When the engine is cold the heat feeler is retracted. In this position the fip is at the rich setting as a warmup aid. If you want the mixture to be richer (higher rpm) during the warm up add washers. If you want to lower rpms during warmup remove washers. Explanation. The wrd pin has a fixed minimum position. If you move the pin farther away from the rack lever the cold starting position will be richer (higher rpms). If you move the fixed starting position of the pin lower, remove washers, the initial or cold setting of the rack will be leaner.
I don't think the wrd affects the rack in any way after warm up. Inside the fip the wrd exerts force on a spring loaded limit pin. Once the limit is reached the effect of the wrd on the fip is zero. It reaches the same stop pin no matter what you do with the round or oval washers. These washers just determine how rich or lean the mixture will be and when the wrd reaches this stop limit. After the stop limit is reached the wrd is has no continuing effect on the fip.
Joe, Maybe you can check my understanding and the function of the spring loaded stop pin.
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Hello Jeff,
I am sitting here with an injection pump on my lap, working all the levers, pins and rods. I know you have a parts injection pump you are learning from also. There is very little information available on these WRDs. I have just searched my early and late BBBs and found them of little help. Other injection pump information I have also is of little use.
So we rely on our own observations and experience for our conclusions.
First of all the BBB uses the shut off temperature as the only basis of the small round shim adjustment. Having to deviate from this seems to indicate that a problem may lie elsewhere. However I do understand that at times deviation may be necessary.
From my observations the heat feeler is in constant contact with the injection pump rack through a series of levers, and cams etc. Yes there probably is a min. length of the feeler but probably a much lower ambient temperature than we will ever see in our climates. Yes there is a max. length the heat feeler can reach, since the spring pin in the WRD will no longer lean the mixture at some temperature. I seems to me to be considerably higher than 180 degrees F. If so, the WRD or the length of the plunger rod and heat feeler of the WRD will effect the main rack and fuel mixture at cold temperatures and normal running temperatures. I base my opinion here on the fact that removal of oval shims always leans the mixture of an engine during warm up and during normal running temperature. I do see that the mechanical movement on one lever is reached at some point above 180 degrees. So at this point, the spring pin in the WRD will no longer allow a leaning of the mixture. If this happens after 180 degree F. (as it seems), then I must still conclude that the WRD is not designed to be able to adjust cold mixture only. Small round shims will adjust IP mixture during warm up and normal running temperatures. Removal or addition of the small round shims or jamb nut adjustment (earlier heat feelers) will change at what temperature the air supply in the WRD will shut down. As mentioned previously deviating from the specified "shut down" temperature may create a leaner or richer mixture during warm up by allowing the extra air supply to stay open wider and longer. This adjustment can only work if round shims are removed and oval shims of the same thickness are added. This basically achieves a leaner mixture during warm up by allowing the extra air supply to the WRD to stay open longer. Hmmm... seems to me you could do the same thing easier by just turning the air idle screw open more, on the intake and leave the WRD alone? Anyway, removing too many round shims, will at some point, cause the extra air supply to never close completely.
Thanks for your input..comments?
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Hello Joe & Jeff,
I find this very topic very interesting, but still a bit confusing.
As I look through the Tech Manual and earlier posts, we dont really have pics showing all of the details you discuss (at least I cant find them).
If possible, could you post pics of:
1. Early & late style heat feelers (i thought the later style has the nuts & earlier w/o the nuts?). My current setup has the heat feeler w/nuts.
2. Clear pics of the round shims for the upper section (heat feeler). I only see pics of the lower section with oval shims currently posted.
Maybe we can then update the Tech Manual with the add'l pictures and description of exactly what the top section (with shims or nuts) and the lower section with oval shims actually does. It would be nice to include in the manual, along with pics, and clear description of:
1. Removal of oval shim from upper section (heat feeler) - leans, or enriches fuel when cold ... or if later style w/nuts, turning nuts towards top body of heat feeler lengthens the rod of the feeler which - leans or enriches the fuel?
2. Removal of oval shims from lower section of the WRD - leans or enriches fuel when cold ..? etc...
3. Specific conditions that apply to removing, adding round shims (or adjusting nuts) on the top section of the WRD, vs. when to add, remove oval shims from the lower section, etc..
I would be happy to help.
Thanks!
Bob :)
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Hey Joe,
I have taken some measurements and can say the air valve closes and pin inside the fip reaches its stop when the thermostat rod moves outward about 3.5 mm. I find this interesting. In a pan of boiling water the thermostat pin will extend 7.8 mm. I think we all agree the air slide valve closes during warmup. It follows that the leaning of the pump also ceases at the same or near the same temperature.
Since the air slide valve and leaning pin in the wrd are part of the same mechanism I think we can conclude that if the air valve closes the pin inside the pump is on it's stop and no further air or fuel adjustments take place until the thermostat cools.
If I get some time I'll cycle water through the wrd mounted on my pump to see if I can determine the approx temperature the pin inside the pump reaches its stop.
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Using a hand pump and 140 degree F temperature water I cycled water through the WRD while mounted to the fip. After a minute or so the air shut off valve closed and the fip pin reached its stop. By the end of the test the water had cooled to approx 130 degrees F. The BBB tells us the heat feeler switches off at 50 to 55 degrees C. I now understand this to also mean the air slide valve will close and the fip pin will rest on its stop.
What do you think Joe?
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Like Jeff, I assumed that complete shut-off of air intake into the WRD should occur simultaneously with the maximum thermostat pin extension once the engine is fully warmed. During my trials and tribulations with the WRD, I discovered that it is possible, depending upon the number of round and/or oval shims, to disassociate these from one another. In such a situation, air may still be sucking into the WRD even though the thermostat pin is at full extension. I eventually came to the conclusion that, at the very least, one must use the correct number of the appropriate shims that ensures that the sliding cylinder completely blocks the air intake port at full warm-up. I identified that it is not only possible for the cylinder to either come to rest just short of fully covering the air intake port, but also possible for the cylinder to slightly overshoot the port and thus cause an air leak.
Once I had determined that I had the correct number of shims to fully shut off air at full warm up, I was then able to use the appropriate other shims to make sure that my AFR, CO, RPM etc was correct at idle.
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Hello Andy and Jeff,
Jeff, ponder this question a bit..... At 180 degrees F. the IP WRD has regulated air and fuel to allow the injection pump to inject the correct fuel mixture, as we understand. Now what happens at 200 degrees or 220 degrees? Are you saying that the WRD just shuts down at higher temperatures and allows the entire mixture to go out of adjustment? I don't think so. I have to believe the heat feeler still regulates the fuel mixture even though the air slide has completely closed, now that a high rpm cold idle is no longer needed.
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Let's say the air slide just closes and the wrd pushes the pin and lever in the fip to its stop when the temp is 130 degrees. At 140 and above the thermostat pin continues to extend compressing the slide valve against the spring/pin just under the slide valve inside the wrd. This compression just adds tension on the wrd pin which is perched on its stop.
At 130 degrees and above the wrd causes the pin inside the fip to sit on its stop. The WRD is simply a starting aid and does not change the rack as the engine warms above 130 de.grees
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If I recall correctly, the length of the cylinder that slides within the WRD chamber is nearly identical to the diameter of the air port in the wall of the chamber. It would thus seem to me that if air is completely shut off at 180 degrees, then any further extension of the thermostat pin (due to higher temps) would reopen the air port as the cylinder slides deeper and begins to open the upper edge of the port.
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Hello Jeff,
I don't think the WRD's main purpose is that of being an engine starting aid. It does contribute to good cold starts by richening the mixture when cold. However, the main purpose of the WRD, is as a "cold running device" which allows the engine mixture of air and fuel to be regulated after a cold start. In this way a richer fuel for cold running is supplied along with more fuel and air for a faster idle when cold. My only area of doubt is exactly at what temperature the WRD stops influencing the rack in the injection pump? I guess we can set up a test procedure for this.
I will say from experience, removing oval shims will normally lean an injection system even on a fully warmed engine. This indicates to me that the heat feeler had not completely reached the stop pin in the pump. Interesting that the stop pin in the FIP has a jamb nut adjustment. There must be an acutual factory temperature setting that is made on these units new. Someone should have this spec?
You have made a very good discovery on the significance of the stop pin. It appears that it does influence the mixture sooner than I would have expected. It does appear that the stop pin does prevent the heat feeler from changing the mixture shortly after the aux air passage in the WRD is closed.
I will check some other pumps in the morning. Sounds like we can come to some good conclussions soon.
One thing I learned over the years, as long as you keep an open mind to new ideas and observations, there is always something to be learned. I guess you could say "to gain expertise you must become an expert learner first!"
Thanks!
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Hello Andy,
I have tested the air passage on this WRD. This one will not allow any aux. air after it closes, no matter how far the piston is pushed down. Eventually it bottoms out, but still no air flow.
It looks like the piston can travel about a 1/4" more after the air passage is fully closed.
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Thanks Joe. (I don't know why I had that impression).
So, if I understand correctly, the hypothesis then is that the WRD may contribute to enriching the air-fuel mixture at higher engine temps?
Then I ask: do air-fuel mixtures need to be richer at higher temps for better efficiency, (and conversely leaner at cooler temps)?
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Hello Andy,
I think Jeff has made a good discovery. I think we both agree at this point that the WRD's influence on fuel mixture, is checked at some point by a "stop pin" in injection pump). This seems to happen sometime shortly after full warm up and after the WRD air passage closes.
A richer fuel mixture is needed for a cold engine.
I believe that the WRD constantly adjusts extra fuel and air to the engine during engine warm up and into warm-up. The extra air is regulated through the WRD air passage and the extra fuel is regulated by the WRD changing the IP main rack. Both the air and fuel changes occure when the "heat feeler" moves the piston and pin under it. At some point in the warm up cycle after the air passage is closed, the heat feeler is prevented from futher moving the pin, by another pin ( "stop pin") in the injection pump (thanks Jeff). The exact temperature at which this "stop pin" performes this stop, is yet to be determined, but it seems to be shortly after the air passage in the WRD closes. We know the air slide closes at a certain temperature as described in the BBB. I have never seen any information anywhere on Jeff's "stop pin". It is a very imporstant discovery and should be very helpful for complete understanding of the WRD.
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There are two springs in the overall wrd system. The upper spring is in the wrd itself and the lower spring is inside the fip under the wrd. The spring inside the wrd, upper spring, is of higher tension than the lower spring in the fip. As the thermo buld expands force is exerted on these springs. The first to compress is the lower spring iside the pump. Once the thermostat forces the lower spring/pin inside the fip to its stop, no matter how much more expansion of the thermo bulb occurs due to rising temps, this pin can not extend any further to change the rack. Once the lower spring has been compressed to its stop the higher tension upper spring inside the wrd simply takes up the difference of bulb expansion beyond that point. If the spring was not there to do so, the pin would be solid ..and then the thermo bulb "could" create enough force to rupture or pop the heads off the mounting screws. Any length changes inside the wrd after the lower spring/pin has reached the stop is taken up by the upper spring.
The air slit opening in the wrd is small enough to be covered by the air slide valve as it to is compressed downward up the upper spring.
Joe, I agree with you about the learning part. If I weren't able to absorb and build on the knowledge you have generously shared I would never have gained this level of understanding about the wrd and other pieces of the 113.
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I'm pleased we now have a complete understanding of the WRD. Joe, thanks again for generously sharing your knowledge. I'll add your description to the tech manual.
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Thanks Joe and Jeff, I get it! Especially now I understand the purpose of the spring inside of the WRD which acts as a safety buffer against excessive pin pressure. Makes sense.
One question remains unanswered in my mind. Is the WRD designed to further lean the mixture above "normal" operating temps (as Joe suggested), or should the fip lever hit its stop simultaneously with closure of air intake?
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Hello Andy,
I think we are all in agreement at this point, that the WRD hits it's stop shortly after the air passage closes. The question of the hour is "exactly at what engine temperature is it supposed to happen?". The "stop pin" in the injection pump has an adjustment feature. I suspect that it is set to happen at an exact engine coolant temperature when the pumps are built. It appears that the influence of the WRD after engine warm up is slight or short-lived.
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Hello,
I guess some good photos are next on the agenda !
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I ran some tests that indicate the thermo bulb deployment at 130 to 140 degrees F is sufficient to close the air slide and cause the pin inside the pump to rest on its stop. No leaning or enrichment of the rack is possible at temps over this range because of the stop. Any additional thermo bulb deployment is absorbed by the spring inside the wrd and below the air slide. The spring tension inside the wrd is sufficient keep this side on its stop no matter what happens on the BC side.
I will take some pics and post them later today.
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The first pic is the air slide valve and wrd pin/spring.
Here are some other pics of the WRD operation inside the fip.
The second picture shows the position of the pin/spring/stop, rack and levers when the engine is cold. Notice the position of the lower right side of the rack lever.
The third pic is a closeup of the pin/spring/stop. There is an outer sleeve which is forced by the thermo bulb to compress the spring to a stop on top of the adjuster nut.
The forth pics shows the position of the pin/spring/stop, rack and levers when the engine is warm. Notice the compressed spring/sleeve resting on the stop and the position of the lower right side of the rack lever.
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WOW, great work on this. I have been reading this with great interest as it has evolved. I have noticed the upper spring on the rod/pin and have wondered what was it's purpose. It makes sense that it prevents the bulb from binding the levers when the pin is on the stop. Given the bulb is some waxy material, it will continue to expand as the temperature increases beyond 140*F. I guess the upper spring keeps that expansion in check without creating excessive stress as Jeff says.
If I understand correctly, are we saying that once the engine temp is 130-140*F, you CANNOT change the mixture at all ranges with the oval shims? If this is true, then what is the best way to do so (BC, full rack screw...)? Then are the oval shims just for changing the fuel mixture with the WRD when the engine is below 140*F?
If the pin is on it's stop, the BC can no longer effect it? If you went up in elevation, you would need to further lean the mixture. How does the BC accomplish this?
One last question. If you removed enough round shims so that the air valve no longer closes when above 140*F, would the pin still be able to close on the stop?
That is one complicated device! I wonder if the guys who rebuild these injection pumps, could confirm some of these findings?
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Wallace,
This stuff is pretty hard to describe so let's use the second picture in my last post. Notice the wrd pin in the upper left side of the fip. There is a preload of this pin on the spring/sleeve/stop and the horizontal control lever at the top of the spring. If you remove oval shims this preload will be lower and the rack will start at a leaner afr. If you add shims the preload will be higher as will the horizontal control lever and the rack will start in at a richer afr. Please understand these are both rich conditions to aid in start and warmup of your engine. The oval shims make this rich condition leaner or richer.
The round shims affect when the thermo bulb starts to lean the rich starting condition. Raise the thermo bulb higher and it will take a little longer to start leaning the mixture. Lower the thermo and it will start to lean the mixture earlier.
Round shims affect when leaning of the mixture begins. Oval shims set the richness of the cold starting mixture.
I hope this helps. It is explained in the BBB if you have a copy.
The BC operates on the right side and tranfers it force via the diagonal fulcrum to the rack. It operates independantly from the wrd. The thermostst pin moves almost 8 mm when heated. It onlt takes 3.5 mm to close the air slide valve and put the spring/pin on its stop.
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Yes, I agree for the most part.
I think the BC works in conjunction with the WRD to change the mixture. The BC is not restricted by the "stop pin" at all, but it does manipulate the same lever that the WRD changes. The fulcrom blends the inputs from the two devices. Also since the pin from the WRD stays in contact with the linkage levers in the pump, It looks like adding or subtracting small round shims directly changes the fuel mixture by moving the rack and also change the amount of air flow in the WRD by moviing the piston over the aux air passage. These changes occure only during wrm up.
Theoretically, removing oval shims should also lean the mixture during warm up without changing the postition of the air piston in the WRD.
Wallace, the heat feeler will continue to move the piston in the WRD even if the pin under the WRD reaches the stop limit. So oval shim removal should not create a problem of with the WRD air supply cut off. Understand that the air piston in the WRD can still be moved by the heat feeler, even if the pin coming out of the bottom of the WRD is stopped by the stop pin in the IP.
I have a good factory diagram of all these relationships, but my scanner is not working at the moment :(
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Andy and Joe
Thanks a million for this! I think the WRD has been nailed in this thread! So I guess the WRD should complete it's "warm up" function at ~55 degrees C (130-140 F), at least with regards to the extra air it allows into the intake manifold, i.e. when it has travelled ~3,5mm. Whether it then subsequently also affects the fuel amounts thereafter i.e. acting on the lower spring any further remains to be solved.
BR,
Ulrik
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Ulrik, thank Jeff and Joe. I'm just tagging along.
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Sorry Jeff, My confussion!! Thanks!! I don't think (hope) nothing else needs to be written on the WRD in the future after this...
Ulrik
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Good stuff.
I hereby nominate Jeff & Joe for the WRD tech session, PUB '11 ;D
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I hereby second the nomination for Jeff & Joe!
I am sorry to run this one point into the ground concerning the oval shims. I understand that adding or removing the oval shims can change the mixture during cold operation. But do the oval shims affect the mixture for a fully warmed up engine? If not, what is the best way to adjust the mixture at all speed ranges?
Thank you for your patience!
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Hello Wallace,
Don't be afraid to ask for more details or clarification. This is basically a brain storming session.
Jeff and others here are some of my thoughts from this information comments welcome....
For most of us, rich running at all speed ranges during the cold engine warm-up cylcle of the engine, is the most common problem. The removal of the oval shims is the best cure for this situation assuming other factors are not causing the problem. This may be as far as you need to go. This is quick and easy and you may not need to go any further, if rich cold running is your problem.
Assuming the pin under the WRD reaches the full stop after warm up, the WRD will not normally change mixture at all speed ranges after the warm up cycle. It will change mixture during the warm up cylcle. "jeffc280sl " discovered this bit of enlightening inflormation. Thanks Jeff !
The internal single screw on the injection pump rack will adjust injection mixture at all speed ranges and all temperatures uniformly. The BC (Barometric Compensator) shim changing will also do this. Adding or replacing the small round shims in the WRD can be used to set the engine temperature at which the air passage in the WRD completely closes. This is a basic factory adjustment and normally does not change much. A secondary effect of changing these shims is a mixture change from the pin going down into the IP also changing length. I suspect that the closure of the air valve should be looked at first, then the oval shim adjustment to tweek cold engine mxture next.
It looks like all the warm engine adjustments should be carried our first if you have both warm and cold engine adjustments to make. If the warmed up engine needs an adjustment at all speed ranges, then the BC or the single internal main rack adjustment screw (not the idle thumb screw) can be used to adjust the warm engine mixture at all speed ranges. If the mixture needs an adjustment at mid or high range on a warm engine, then the two pair of internal governor screws can be used or (see option below). If the warmed up engine is in need of mixture adjustment only at low rpms and idle, the idle thumb screw on the IP or the intake air screw may be the only adjustment needed.
The option....Here is a situation, say you determine that your warmed up engine is fine at idle but rich at mid and high rpm ranges..... The best solution I see would be to do a total mixture adjustment at the BC or the single internal rack screw. This would cure the mid and high rpm issue but cause the idle mxture to become too lean. Next I would adjust the idle thumb screw to bring the idle into correct mixture. This sequence would avoid the need to do internal governor adjustment on the two pairs of range screws.
After warm engine adjustments have been made. The WRD air valve should be checked to make sure it closes at the correct temperature (small round shims). The mixture at cold idle can be adjusted by adding or subtracting oval shims.
I stress the importance of checking first, things like correct linkage adjustments, plugged WRD air filters, stuck WRD pistons, engine vacuum leaks, bad Baro. Compensator units (BC), bad heat feelers in the WRD, leaking intake starting valves, poor engine tuning, and bad fuel pressure or fuel volume. These other faults may just cause you to make uneeded changes on your complicated injection systems if you do not fix them first !
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I agree with Joe especially the part about checking everything else first. I think everything else includes checking the thermo bulb and slide valve in the WRD. This is just like making sure you have a good bc. After everything else is checked and fixed then you can begin to think about changing shims and other fip adjustments.
If you choose not to check and repair everything else first you will be chasing your tail with fip adjustments.
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Adding or replacing the small round shims in the WRD can be used to set the engine temperature at which the air passage in the WRD completely closes. This is a basic factory adjustment and normally does not change much. A secondary effect of changing these shims is a mixture change from the pin going down into the IP also changing length.
Sorry to be late to the party, but I'm working on a WRD that doesn't close all the way despite being clean and having an operative heat feeler. My conclusion is that I need to add some shims between the heat feeler and plunger assembly.
When first thinking about it, I was thinking the same as Joe in the above quote, namely that adding or removing round shims would change BOTH the temperature at which the air valve closes completely AND the mixture during warm up. But the more I think about it, I don't think that's true. Changing the round shims moves the whole plunger assembly in tandem. The point where the air valve closes is exactly the same as the plunger protrusion that affects fuel. Adding shims moves the air valve a little bit further closed, but it also moves the fuel plunger to a commensurately leaner position - exactly the same as without the shims, just at a lower temperature. It's the relative distance between the air valve and the pin that determines mixture, and that distance is changed only by the oval spacers.
Does that sound right? I'm thinking I can add round spacers and not screw up my warm-up mixture.
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I removed round shims until my WRD air suction would not shut off. That ended up being .025" on my car. I suspect it is similar for most. What thickness of shims do you have?
Adding round shims does reduce both the air and fuel although I am not so sure it is 1 to 1. If you look closely at the orifaces in the WRD where the air comes in from the filter, there are three rectangular grooves that resemble an upside-down pyramid. The smallest groove is for higher starting tempertaures, the middle groove (including the small groove) is for cooler starting tempertaures and the largest groove (all three combined) is for very cold starting temps. And changing the round shims does affect the temperature when the WRD shuts off.
Because I am not 100% sure the air and fuel change at the same rate ( I doubt they do) when adding shims, you may have to adjust the lower oval shims to compensate. But that is no big deal. The round shims are harder to change.
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There is a difference between the 230Sl system and the later 250/280SL system. They do the same functions but the parts are not the same nor do they work in the same ways.
The 230SL thermostat has a very short travel at about 1.5 mm while the 280SL has about 7 or 8 mm of travel. If the late system won't shut off at a fully warmed engine, you can add round shims at the top of the slide valve until there is no longer any vacuum with the air filter removed.
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I've has some air slides that leak, allowing a constant bleed even when fully closed. A coating of copperslip usually seals it up but the treatment needs to be re-applied at every service.
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Adding round shims is my plan. Thanks for the confirmation that's the right approach. I tested the device when I had it apart and it seals nicely as long as the plunger is down far enough. I had also measured how much plunger movement was needed to close the valve, and measured the throw of the heat feeler and it measured out to be just enough to close the valve, but apparently I was off just enough to not get full closure This time I'll test the whole thing fully assembled before refitting to the car. All this draining and refilling the cooling system is a pain in the neck.
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To keep the WRD thermo housing from leaking everytime I remove it to adjust the shims, I used a Permatex product and it worked perfectly. This is NOT like a standard RTV silicone. It is much, much tougher.
http://www.permatex.com/products/automotive/automotive_gasketing/gasket_makers/auto_Permatex_Ultra_Grey_Rigid_High-Torque_RTV_Silicone_Gasket_Maker.htm
I probably took the housing off 10 times and it never leaked. I spread a thin ribbon of the "Ultra Grey" sealant on the beveled contact face of the thermostat bulb. I then placed the thermo bulb inside the housing and used the seating washer to mash it and make sure it was straight. I spread the excess around the bulb leaving a small bead around the bulb. I just let that sit overnight and it is done.
In fact, I just removed the bulb from the housing last week so I can plate the housing. The sealant was in great shape after two years and was somewhat difficult to remove. I will use the Ultra Grey again when I reinstall.
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Sorry to drag up an old thread....
I have what seems to be a common problem with my '68 280SE in that the engine runs far too rich on the warm-up cycle. I tried following the advice here by taking away shims from below the WRD, but on removing the bolts, there don't appear to be any there.
The engine runs fine once it is warmed up, and although it runs very rough when cold, it starts without a problem. I know the WRD is working, as I can hear the air rushing through it when the engine is cold, and the engine has a high idle speed that reduces once the engine warms up.
I have checked the linkage to ensure that it is within spec. I've also checked that the cold start valve is not leaking.
Does anyone have any ideas what to look for next? It's more of an annoyance than anything else, as once the engine is warm, it all runs perfectly.
Thanks
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First you need to confirm that the mixture is in fact not overly rich when the engine is warm. It might well be running fine but that doesn't mean that the mixture is correct.
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What Stick said and:
The WRD air filter may be highly restricted.
Make sure the shims aren't stuck to the bottom of the housing. They are typically very thin , .003" to .020".
I suppose the thermostat rod could have worn enough not to need shims, but that seems unlikely.
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Thanks - will have a look again for the shims. It's a possibility I didn't spot them. I'll see if I can remove the air filter on the WRD. It does seem to be letting air through though, as it makes quite a loud sucking sound.
I don't have a gas tester, so can't really tell whether it's running rich when it's warm, but I've pulled the plugs, and they're a nice brownish colour, so I'm guessing its OK. That said, it does kick out a bit of smoke when I floor the accelerator. I have checked the linkage according to the 'linkage tour', checked the ignition timing, and adjusted the valves, so I'm running out of things to check. The car has only done 80,000 miles from new, so I'm thinking it unlikely that things will be that worn out.....
The most annoying thing about this problem is that I only have about 10 minutes to do any adjustments before it warms up.
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You can check the mixture by doing the split linkage method. I use it all of the time and works well hot or cold, for idle or higher RPMs. Do a search for split linkage and you should find it easily.
If you get the air filter off using a thin wrench, you can do a simple test to determine if the filter is too clogged. Again, do a search and you should find it. There was a post recently about that.
I learned these things along with 10,000 other things on this site. Join and become a full member. It is well worth it!
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Just to update (by dragging this thread up again).... the rough running when cold turned out not to be anything to do with the mixture in the end - using the 'split linkage' method I ruled that out. I also made sure the WRD air filter was clean.
The problem sorted itself out after I took the plugs out to do a compression test (which was fine), and cleaned them with a cloth before putting them back in - they were a bit fouled. I've now changed to NGK BP6ES plugs from the wrong resistor type ones that were in there, they haven't fouled since, and the car runs smooth from cold. I did a 400 mile trip the weekdnd before last, driving the car hard (cruising at 80mph), and it's running better than it ever has since I had it.
Moral of the story - correct spark plugs make all the difference, and these cars like a good run once in a while. The advice from this site has been invaluable though - you're right - I really should become a member!
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The BP6ES NGK plugs cross over to the old W7DC Bosch plugs that are no longer available. I found that W7DC plugs were too cold for most aplications so I witched to W9DC. Now that they're also no longer available, I now use BP5ES which are closer to the old W9DC. These slightly hotter plugs seem to work better by heating up faster during the critical starting and warming up period.
In short, I don't even bother with anyting but BP5ES plugs now.