1967 Mercedes 230sl Engine Trouble

[afisk]

Hello,
I have been working on a '67 230sl that has not been started for 24 years. This car has a mechanical fuel injection system. I replaced the fuel pump and fuel lines, cleaned the tank, and replaced old fuel filters and was able to get it running. I drove it for 50 miles and then it started acting up. The engine no longer idles and I have to constantly apply pressure to the gas peddle to keep it from stalling. I rev it to 1000 RPM to keep it from stalling, but when it revs at this RPM, the engine misfires constantly. I am trying to find the root of the problem. I readjusted the gap on the points, which are in good condition, and changed the plugs and wires. I am getting a good electric signal to the cylinders. I pulled the new plugs out and noticed that they had extensive carbon fouling. This lead me to believe that I am burning too rich of a mixture. I am unsure where to precede from here. Any advise would be much appreciated.
Thanks

[jedwards]

Others will be far more experienced than I, however as you clearly have an over-fueling problem bought on following a 50 mile drive, the main culprit would surely be debit from the fuel lines caught in the Cold Start Valve which would create all the symptoms you outline.   There is great information on how to remove and clean the CSV in this forum and a simple task to tackle irrespective of your experience level.
Good luck and let's hear how you get on.

[w113dude]

If the car hasn't been driven for that long you should start with the basics, make sure your linkage is right first.

[Benz Dr.]

It sounds like it's too lean. You probably have a restriction in the lines or fuel tank.

[afisk]

I checked the cold start valve (which I am assuming is the valve at the far right of the intake manifold) and it was working like it should be. The screen within the valve was not clogged and the valve was not stuck open. I even disconnected the wire going to the solenoid of the cold start valve so that it would not operate, so I do not believe that the cold start valve is the issue. I checked all of the linkage and it is correct. I took the fouled plugs out and cleaned them off and then put them back on the car. The car ran fine for 10 seconds but then the plugs became fouled again and thus made the engine begin to misfire. On the side of the fuel injection pump, there is a screw you twist either clockwise or counterclockwise to make it burn richer or more lean at idle. I adjusted that screw to allow the engine to run on the lean side, but that did not solve the problem. I don't understand why, after getting the car running after sitting for 24 years, the engine ran great for 50 miles and then after 50 miles all of these symptoms arose. I drove on the highway for 40 of those miles. There almost seems to be a valve in the fuel injection pump that is stuck open allowing all of this excess fuel to enter the cylinders, but I do not want to disassemble the fuel injection pump unless I absolutely have to. Any other ideas as to why the engine would be burning so rich causing it to stall?
Thanks

[jackmc]

I have a '64 230 SL that required a new engine back in 2010.  The car had been sitting in my garage for about 8 years without running.  I purchased a short-block for the engine change as I had already removed the head and was having it overhauled.  When I reassembled the engine I used all the auxiliary equipment that was on the old engine.  My major problem on attempting to start the new engine for the first time turned out to be clogged/sticking fuel injector nozzles in the head.  They are designed to remain closed until the fuel pressure reaches a certain limit and then only dispense fuel until the pressure drops below the lower limit thus allowing only a short burst of fuel for each piston stroke from the injection pump.  I found that when they stuck open my symptoms were identical to yours (fouled plugs and rough running).  I could only get the engine to run semi-smooth when the RPM got over 3000.  I found a shop here in Tucson that has the equipment to test the injectors and found some completely clogged and others that were always open.  I postulate that your fuel injector nozzles may be stuck open because of residue from the gas that was still in the lines during the time it was not running.  I ended up finding some used nozzles that worked properly and thus saves some dollars but new ones are available too.

I hope this helps.

[Cees Klumper]

You also want to check put that other possibility, that Dr Benz suggested: a lean condition. The tank has a complex thing inside (dubbed 'the flower pot' by the same Dr) that can become restricted. Measure the fuel flow / pressure to make sure this is not your problem. Good luck and keep us posted.

[ja17]

Check to make sure the WRD on the injection pump is not stuck.  Dis-assemble and clean it if needed.  This is not difficult. No inection pump removal required.

[afisk]

@ Dr. Benz & Cees Klumper, if it were too lean, wouldn't that mean I am not getting enough fuel to the cylinders? Because it seems that I am getting the opposite problem with the extensive carbon fouling.
@ ja17, I am unfamiliar with the WRD on the fuel injection pump, could you explain more as to what its function is? Also, do you know where the WRD is located on the pump?
As always, thanks for the help.

[Cees Klumper]

The WRD is the warm running device, its function is to temporarily increase the fuel/air mixture during cold start-up. It is situated towards the rear of the injection pump, closest to the firewall, and looks like a little tower with short hoses going to and from it. Do a search here, or look through the technical manual, this topic is probably one of the most extensively covered on this site.

[garymand]

I agree with the rich.  I just had my altimiter not hand tight enough.   At 70, it backed out many turns and the motor turned into your symptoms.  So hand check that the altimiter is tight (round pot next to the WRD, on top of the FIP), the WRD would more likely fail on start up rather than while driving, injectors are a possibility.  This is a little different where it starts to run crappy while at speed.  Like my altimiter coming loose, this sounds like a link rod wasn't as tight as you thought and it has self adjusted to very rich.  I've had tha happen too!  Hopefully it is one of the easy loose things.

[Benz Dr.]

I had one come loose once too - it had to be towed home. Had it fixed and running in an hour - no tools with me.


This may sound strange but it might be lean and rich at the same time. ( I bet no one has ever come with that one  )  Lean because it lacks fuel pressure and volume; rich because the injectors could be faulty.

[garymand]

Nice, I like that one.

[wwheeler]

I have a rich and lean condition right now. Here is my theory.

#4 fuel line is only providing half the fuel that the others are (discovered by testing). That #4 spark plug is running extremely lean where as the other plugs are correct. Since the fuel volume is so low to #4, the spray pattern is more of a dribble instead of a fine mist. It doesn't burn completely sending unburnt gas out the tail pipe resulting in a very rich smell.

The cause is sitting for a year and a half for a large project and the gas went bad. Where the restriction is in #4 is yet to be determined but will be soon.

[afisk]

Upon working more on the car, I have found that the WRD is not working properly. When the engine temperature is at 170 F there is still much air being sucked into the WRD. I discovered this by removing the air filter on the WRD and listened to it continue sucking in air even after the engine was up to temperature. I took the part on the top of the WRD that has the two hoses of coolant running to it and found the brass thermostat that has the pin on the bottom. This pin is supposed to extrude from the brass thermostat when the engine is warm enough. By doing so, it would shut of the spring mechanism that is within the WRD. I pushed on the spring mechanism within the WRD and it moves freely, so I do not think that is the problem. I believe the problem is the brass thermostat, but I do not know how to fix it. I called mercedes and that part is no longer available. Are there any ideas as to where I can find this brass thermostat (after market parts?) or is there a way that this thermostat can be fixed?
Thanks for the help

[66andBlue]

Have you checked the thermostat to be sure that the pin does not move? Put it in the fridge and then in boiling water. The pin moves only about 4 mm.
If it is dead call Gus at Pacific Fuel Injection or Hans at H&R Fuel Injection and see whether they can fix it.
You can find both companies here: http://www.sl113.org/wiki/Suppliers/Start

[ctaylor738]

Maybe you have seen this:

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

The actual movement of the plunger is only a little over one mm.  But with the adjustment you have some leeway as to where the movement starts and stops.  You may have to sacrifice some cold enrichment to get it to close fully once warm.

Good luck,

[Benz Dr.]

Nice, I like that one.

Nah, it's all BS - but it sounds good.

[garymand]

1mm is pretty small,.1 millimeter = 0.0393700787 inches, sorry .040.  tha is about 1/10 the travel you need.. I'm not sure what's in the 230 WRDs, Pictures here I've seen only show the air piston for the early ones.  My 250 and 280 versions have the shim adjustments not a screw type on the air.  Regardless, the thermo thing  moves the air piston from fully open to fully closed air flow through the WRD.  Yours isn't closing and it is only moving 1mm?  Go on Ebay and buy a new thermo thing.  I know I've seen them recently.  You'll see the brass bulb 'ampoule' and shaft with a stainless steel clip holding the shaft in. 

I was told a long time ago, the brass thing is full of wax sealed with the rubber channel that holds the shaft under vacuum. (no air)  If you pull the pin out or it is somehow squeezed all the way out, air gets in and you will have a meam time getting it to woirk right ever again.  (don't ask how I know,  ).  Maybe some one hear has a trick to get the ampoule to work right, but I didn't want to chance having it prematurley going bad again, so I bought 2 back in 1980.  Some thermostats have the same device opening the thermostat. 

It won't hurt to get the WRD working right, but I have a feeling that isn't the root.

[Benz Dr.]

You're probably thinking about the 280SL style thermostat which is as you describe it. The 230SL type is a long cyinder and is very exspensive compared to the 280SL. I know the movement is quite a bit less with this system than on the later pumps but I'm not sure of the exact amount.

[garymand]

I learn something new each day... now I know another reason why I went with a 250 not a 230.  So, how does 1mm movement of the thermo ampoule open and close the air piston?  Does it only move 1mm?

[66andBlue]

Maybe you have seen this:
http://www.sl113.org/forums/index.php?topic=14677.0.
The actual movement of the plunger is only a little over one mm. ......

Hi Chuck,
here is what you wrote earlier in the linked topic:
"Well, I talked to Hans again this morning and he confirmed that 1.1 mm is the spec for th R-11 WRD.  You of course need to measure it with the rod against the plunger because it will freely extend another 2-3 mm."

So If you take the sensor out and test with hot water it should move about 4 mm. Correct?
How would you do the test when it presses against the plunger below? Tough putting both of them in hot water together 

Garymand,
we are discussing the WRD on a R11 (230SL) injection pump NOT the later style pumps on 250SL and 280SL that have the newer sensor!

[ctaylor738]

DOH.  Good point.

I think what I meant was that if you press the plunger all the way in when cold and measure how far it extends, then put it under the instant hot for a minute and make the same measurement, the difference (extension) will be about a mm.

Cheers,

[afisk]

I have solved the carbon fouling problem, although not how I would have liked. I pulled the thermostat from the warm running device and put it in the refrigerator and then into hot water and I found that the thermostat is not working. I called Mercedes and they cannot get that thermostat anymore. I will have to look into possibly repairing the thermostat. I then took the whole WRD off and found that the plunger can be manually closed by twisting a nut on the outside of the WRD. This nut has a piece of metal attached to it. This metal piece is within the WRD and rests on top of the plunger/spring mechanism that closes that valve when the engine is warm. I adjusted the nut so that the piece of metal depresses the plunger fully, which in-turn shuts off the extra air and fuel that is needed during warm up. The WRD is currently always shut off. The car starts a little rough when cold and then runs fine after running for a few seconds. The plugs are no longer fouled. If I am not able to get the thermostat repaired or I am not able to find a new thermostat, is it acceptable to run the car without the WRD? The only issue that I can see causing a problem is a hard start up.
Thanks

[66andBlue]

... is it acceptable to run the car without the WRD? The only issue that I can see causing a problem is a hard start up. ...

A similar solution was posted several years ago by lurtch, see reply #4 here:
http://www.sl113.org/forums/index.php?topic=5460.msg33780#msg33780

Send Larry a PM through the mail system here and ask whether he is still running his engine that way.