Frustrated with my 190E
 

I have a 1989 190E with a 2.6 engine, the car mixture has been on the rich side for a while, I know it because of the black smoke, now after a month of this the engine just quited, these is a description of the problems: the engine will start for a few seconds and then it will stall, if I press the gas pedal down the engine will stall anyway, if I keep on starting the engine it will not start anymore, after close inspection of the sparkplugs I found that they would be wet with gas, I have a good spark, I have checked all the ignition system and is ok, the fuel system is another story, there is a fuel or mixture regulator that is attached to the fuel distributor that is leaking gas thru a small vent hole? I adjusted and cleaned the plunger of the fuel distrubutor and I have to check fuel pressure. Any hints on my case?.....................

One possibility is that your O2 sensor died a while back and continuing to run rich killed your catalytic converter. With blocked cats, your engine won't run for very long. If your cold start valve is leaking or is stuck open, it might do the same thing.

Sixto
91 300SE
81 300SD

It is easy to get over your head in a situation like this. Start with the basics and if you can't get it, you may want a pro to look at it.

Just a thought.

Benzmac's right...

However, you may check your fuel pressure regulator. I'm only saying this because I had similar problems on my car and after replacing a couple of parts, addressing this part cured it. Of course, you can do a fuel pressure test to confirm. Good luck.

Fuel leak
 

I'll go along with Donnie on this one, however the unit your talking about is most likely the Differential pressure regulator (DPR) or MB speak (EHA)
If it's leaking in the back it needs replacement. In the front you could get lucky with O-rings.
NOT LIKELY!
On this car I believe the Pressure Regulator is part/internal of the Fuel Distributor, but serviceable.
Replacing it might solve your problems, you should still have a pro
take a look at it.
Someone that knows what theyr doing will save you $$$$ in the long run!