C230 Kompressor cold start issue..
 

I have 2000 C230 Kompressor, and have noticed when the temp has dropped to around 0-20 deg. F, the car cranks and cranks. It might take between 5-10 cranks at 10 sec each before cars starts. Once car starts, runs great. I am suspecting loss of fuel pressure. Once car is running, never stalls, or any lack of performance. I have read on here check the pressure regulator, the air mass meter, and the OVP. Not sure where the OVP is on this particular model, and wondered if it had one. Once the car starts, and warms up, it starts well during the day, unless left unattended for more than a few hours. I have also considered coolant temp sensor. Any help towards diagnosing this would be appreciated, took to dealer and they couldnt find anything wrong (they still wanted paid of course..lol).

Just 2 questions.
1. Does the Check Engine light come on?
2. Have you checked the actual fuel pressure ?

I have never had an engine light come on (yet). I had taken it to a dealer to check it out; I know the codes were checked on and cleared, I want to assume they would have checked the fuel pressure, but you can't always assume they would do something that would be logical. This morning I am going to check the vaccuum hose leading to the regulator when I get it running, to see if the diaphram inside is leaking. Another thing I forgot to include, if the car has sat for an hour, and not gotten completetly cold, it will start, but chug a bit before the idle smooths out.

I believe a defective regulator diaphragm would cause driveability problems, check engine light, etc.
A pressure test ( running & residual pressure ) would be my next move.
You probably have to leave the car sit overnight, with the gauge connected, & look at residual & start-up pressure in the morning. ;)

I wasnt sure if a diaphram with a hole in it would cause a check engine light or not. I was also thinking maybe I am getting a weak fuel pump, and the cold is affecting it. A question: Are those fuel pumps inline pumps along the frame, or mounted in the tank? I am praying the buzzing sound I heard from underneath on the frame rail was the pump..lol. Also, is there a check ball or valve between the regulator and the pump, maybe in front of the pump directly? I really need to buy a CD shop manual..lol. I am going to check the schrader valve on the fuel rail (cannot locate my fuel pressure gauge), and just see if I have any spray, or if it feebly leaks out.

If you look ( from the rear of the car ), to the left of the right rear wheel you will see the fuelpump & filter.
They have a shield under them, but you can see both.
For a manual, you can go to: www.books4cars.
That's where I got my Haynes manual.
It does not cover the " Kompressor " specifically, but it's better than nothing. ;)

Figures..now that the temperature here is Omaha is getting to the 50's and 60's, my problem has ceased to be. One cold morning, I did get it to start right off by cycling through turning the key on and off, to get the priming effect a few times, and it fired right off. Then the next morning, it was already 40 out..so not sure what to think. I will be buying a fuel pressure gauge today...I need one anyway..see what is going on. Good to know the fuel pump isnt located in the fuel tank..thank you nameless Mercedes engineer on that one!

That smells like a fuel pump/pressure problem to me.

Well, not a fuel pressure problem...have checked the pressure on many occasions now, and holds pressure over night, and still has a tough time starting..starting to maybe lean toward a faulty coolant temp? Instead of reading too cold a temp, maybe too high and its too lean to fire. The mechanic I am working with is puzzled as well (no codes, and values seem to be fine...)..will update...

FWIW.
Most temperature sensors ( air, coolant, etc. ) work on the same principal.
High resistance like 10 k ohm indicates cold, while low resistance, such as 100 - 300 ohm indicates a warm/hot condition.
So, maybe if you disconnect the coolant temp. sensor, the ECU would see this as a cold engine.
Doesn't cost anything to try. ;)

I am going to try that...have been at the local repair shop, and they are baffled to the point of being really curious. No codes, but I wonder during the start cycle, and when the engine is in closed loop or cold mode, if the injectors are even firing. Which really opens up a can of worms...Crank sensor, the auto-start not sending enough voltage for start ups, am going to try to put a test light on the injector wire loom to see if I get any current blinking at me during the crank up. I have a feeling the shop I am dealing with is relying too much on their scanner (no use pointing at the cut wire..computer says it isnt there.....). I will try the coolant temp test directly after posting this. Otherwise, this being my first Mercedes, love the car (was driving my old car when this one was in the shop, a 94 Olds LSS...always thought that was a decent car til I got back in it..lol.