I'm looking for any info about "basic adjustment of control piston in fuel distributor". I was checking sealing ring for control piston, but before taking it apart I didn't measure an exact position of closing plug. I know, now I have a problem. I did put it back together but something if off. Now my fuel mixture is rich and using a duty-cycle meter I can't get reading any higher that 39. Also car is hard to start when cold. My question is:"How can I put/set plunger properly? What is the way of doing it?"
I guess that I can keep playing with it but I would prefer more professional way.
Thanks, Derek

MMMMMMMM,
I have never seen this done with any success. I think you may be getting a new one.

300SEL - Distributor Piston
 

I've been there. Lucky forr me that i measured the clearance before I removed it. However, as long as you were careful with the plunger, you should be able to fix it. You can get a Bosch fuel injection manual(available at many bookstores) or preferably the CD MB manuals. These should give you the plunger rest cleanance. It also appears, , based on what you have told me, that you need to readjust the mixture setting on the flowmeter air sensor. This is easy to do and is spelled out in the manual.

Looks like I had some luck. I got it to work, but something new showed up. In my original post I said that I could not adjust mixture and reading was showing 39%. It is actually 40% staying steady on idle. M-B service manual tells me that it is an air flow meter sensor failure. Is my troubleshooting correct and if yes, can I replace just that electrical sensor or whole assembly with flap (less distributor) will have to be new?
Derek