Question about auxillary air valve thermostat

[salvine]

Hello. New here but not new to MB. I have been lurking for awhile to gain information while I help a friend get his 66 230 up and running. We have a pretty bad issue with the car running very rich while cold. I have been looking at several things that can cause this in including a leaking CSV. One of the items that looks suspect is this thermostat in the injection pump. I believe it also adjusts mixture as well as closes the air valve correct? My question is, how much does the little pin travel between cold and warmed up? I know there are two versions of this unit and this car has the very rare one. Read the one that cost upward of 1000.00 if you can find one and not the 30.00 one that is easy to purchase. I measures the pin length cold at 1.5mm extending from the housing and 6.7mm hot. As luck would have it the owner has a complete injection pump in his garage. I grabbed that thermostat and measured it at 1.8mm cold and 7.2mm hot. Either this is normal or I have two very tired thermostats. In my mind it could be they are both bad as I'm quite sure they are both 30+ years old. Any info on this or other ideas on the rich condition?

TIA, Steve

[ctaylor738]

It sounds to me like the thermostat is OK. 

It is possible that:

- the thermo-time switch is malfunctioning and and keeping the CSV squirting longer than it should.  Use a meter or test light to check

- the WRD is making the pump supply extra fuel, but no air.  Can you feel suction with the air filter removed?

- the cold-start solenoid (on the back of the pump) is not releasing when key goes from start to run.  Test with a light or meter.

But I have to ask - how do you know it's running rich and not lean when cold?  Most problems with cold running are too little fuel, not too much.

Cheers,

CT

[jeffc280sl]

Welcome,

When starting the car when cold you should here a noticeable rush of air being pulled through the small air filter on the injection pump.  As the engine warms and the  thermostat element extends, as described in your test, the air valve will close and the rush of air through the filter will cease.

As suggested you can remove the air filter.  Now start the engine when cold.  You should hear and feel a strong air suction at the pump where the filter is threaded to the pump.  As the engine warms the air valve will close and there will be no suction at this location.

Br,

[salvine]

It sounds to me like the thermostat is OK. 

It is possible that:

- the thermo-time switch is malfunctioning and and keeping the CSV squirting longer than it should.  Use a meter or test light to check

- the WRD is making the pump supply extra fuel, but no air.  Can you feel suction with the air filter removed?

- the cold-start solenoid (on the back of the pump) is not releasing when key goes from start to run.  Test with a light or meter.

But I have to ask - how do you know it's running rich and not lean when cold?  Most problems with cold running are too little fuel, not too much.

Cheers,

CT

After more searching it looks like my thermostat has the correct travel length. I do have the air being sucked in at the valve and then lessening as the engine warms. I will be spending some tome with the far on Fri so I may have better info then as to what is working and what is not. I'm sure the mixture is rich due to the amount of black smoke and the plugs need to be removed and cleaned every couple of minutes. It fouls them and then starts to miss very quickly.

[alchemist]

My thermostat extended about 7 mm from cold to hot, it seems that yours is working. You can check if you have oval shims underneath the WRD, if you do, then remove them that will lean the mixture. I have 2 oval shims and my start is lean, I am planning to add some more. Good Luck.

[salvine]

It looks like the valve on mine has a threaded shaft with a lock nut to adjust the air valve. Does this valve also adjust something on the pump as well to control mixture or just add air to the warm up cycle like a modern idle control valve?

[ctaylor738]

The thermostat moves the slide valve, and the pin that extends below it moves a lever in the pump that controls enrichment.  As the engine warms up and the bulb in the thermostat expands, the air valve closes and enrichment is reduced.  If you use the adjusters to lengthen the plunger rod, the air and enrichment will shut off sooner.

But from what you are saying, I think this amount of extra fuel is beyond the WRD to supply, and that you should check the starting aids for correct operation before messing with the shims or the length of the rod. 

Cheers & good luck,

[jeffc280sl]

Can you post a pic of the lock nut?  Can't imagine how that would work.   I have seen examples where a threaded bolt and lock nut was used in place of the baraometric compensator.

[ctaylor738]

There's a picture in this thread.

http://www.sl113.org/forums/index.php?topic=14677.0

[salvine]

Mine looks just like the one in the photo in that thread. Could not get it to start with everything hooked up. Loosened the screws for the thermostat to back off tension on the valve below and then the car fired right up. Ran for a bit but then as the the rod in the thermostat extended it got really rich again and died. If I hold it on a high idle it helps a bit but still fouls out.. The cold start valve appears to be working. Only has power while cranking. What's with the eccentric bolt on the side of the housing. Mine is set to to allow the valve to come up to the highest point if that makes sense.

[ctaylor738]

Sorry, I can't explain what you're seeing.  As I read it, you have to back off the WRD from the pump, which would make the mixture richer to get the car to start.  OK that makes sense.   Then as the pin extends it is supposed to lean the mixture, but you are seeing it go richer. and stalling the engine.  Correct?

I think you are right that the knob adjusts the starting point of the valve/plunger, so if is allowed to come up to the top position, the valve will take longer to close off the air and lean the mixture.

[ja17]

Check the rack on that injection pump first. It could be stuck.

[alchemist]

Check if your starting aid valve is leaking. There is a 6mm nut on the side of the CSV. While the engine is running, unscrew this nut and see if it spits any gas. If so, the CSV valve is stuck open and in need of cleaning, this usually causes the enrichment of the mixcture. I hope this help.

[salvine]

After a little more fiddling I have it running and not fouling the plugs. Still a bit rich but it will drive. Then the old car blues set it. The shift linkage fell off so new bushings were needed. Got those and installed and then the car would not back out of the shop as the L/R brake was bound up. Fixed that and replaced the leaking wheel cylinders only to find the flex line to the R/R brake was blocked. Replace that hose and re-bled. While the car was idling in the shop the radiator blew! Oh the humanity! Any recommendations on where to get one of those? My usual parts places are no help. I want new since patching this old one is probably a wasted effort.

[Jonny B]

Don't be too quick to write off the old radiator. When you type "blew" did one of the row of tubes fail, or was there a problem with the top or bottom tank? These can be recored (use three row for better cooling). Finding a place to do the work may be a bit of challenge. This has been typed about before on the forum, so try the search function.

A quick look at Millers site showed $550-$900

[salvine]

By new I guess I meant not just getting it repaired since I know there other problems with it. There are local shops that can re-core it most likely. Just need to call them. Millers site?

[Jonny B]

One of the vendors for the old MB's is Millers Mercedes. I only used them as an example, as there are a number of other folks Buds Benz, K&K, SLS, Authentic Classics for example. Check out the vendors listing