Hello Everyone..
I am new here on the forum...I will be grateful for your attention and help, and at the same time I will try to help you too.
I think I have a big problem with my car, it's a Mercedes W203 C200 compressor from 2000..with engine M111.955..
I've owned it for 12 years and I've never had a problem like this...
The problem has started since February until today, when the fuel pump in my tank started leaking...
Since then, I have a problem with cranking after a long time when the car is stationary and the engine is turned off....
That certain time period of standing is about 3 hours, when the engine is long cranking... and the fuel pressure in the system drops to 0 bar...
I replaced 3 fuel pumps in the tank, 2 fuel filters, 2 pressure regulators on the rail, and if it doesn't have any function, does the fuel on the rail not return to the tank....I replaced the cam sensor and the crankshaft sensor....I replaced all the rubbers hoses around the fuel filter, thinking that one of them is not causing a problem, that there is no fuel leaking somewhere... I changed the spark plugs and the ignition coil... I checked the hoses in the tank from one chamber to the other that they were not punctured... I measured the engine compression which is on 8 bar...the car has 340,000 km...tried to pour fuel directly into the cylinders...checked all 4 injectors so that none of them are leaking...all I have to do is replace the engine ecu...any idea I don't have any anymore...The engine does not emit blue smoke or consume oil...I invested about 1000 euros in car parts for this problem, for a car that is not worth that much
And the whole problem is that when the car is standing for a long time, the fuel pressure in the system drops to 0... the moment I turn on the pump, it immediately pushes up a pressure of 3.8 bar... and the car long cranking for about 10 seconds, until it starts ..and then it works without problems...I turn it off and every subsequent cranking within 3 hours starts immediately without problems...as soon as the engine is turned off for a long time of 2 to 3 hours and if during that period the pressure is about 2, 5 bar in the system, which is quite enough, the engine operates long cranking for about 10 seconds and it starts... and when the engine is running, it runs completely smoothly, there are no disturbances in operation... the car pulls well, runs without problems, the gas consumption is factory 9 liter per 100km...everything is perfectly fine without any problems...Diagnostics does not report any error but nothing....
I'm just saying I haven't tried replacing the engine ecu yet...
And I'm wondering if the valve located at the left headlight, the valve for irradiating the tank, has any function regarding the ignition?
I started to lose my temper with the car and we have moments when I wanted to set it on fire
I would be grateful to all of you who read my problem and give me any advice or help...what could be the problem....
Thanks

 

Sounds like you're just throwing parts at the car at this point. Best not to do that.

Are you installing a quality fuel pump? (dealer or Bosch)

Are you installing a quality fuel filter? (dealer or Mahle Knecht KL-82) - this is the only model I would trust. Other aftermarket filters are known to have issues with the pressure relief valve, which leads to problems in the fuel rail.

What is the last thing you touched before the problems appeared?

 

The fuel pressure should be above 2.5 bar after 30 minute shut off. I remember the compression must be above 125 psi ?

 

Fuel pump is Pierburg....fuel filter is Bosch....
Regarding the pressure, I have never checked before whether it is always present in the system no matter how long the car is not driven...does it always have to be at 2.5 bar even if the car is not driven for a long time or only for a while... but as soon as I turn on the ignition, the pump immediately turns on and that pressure is 3.8 bar....And according to the factory data of this car that I found on the net and some car programs...the compression is 9.5 bar....which the masters think is this compression of 8 bar for a car 24 years old and 340000km quite good

 

It decreases to 0 after some time,that's why the specs says 2.5 after 30 min.
You changed all I would think of already. I would probably measure this 30 min value to exclude some minor leaks. 3.8 on idle is fine.

 

I measured the time... after 30 minutes the pressure drops to 2.5 bar, but it doesn't stay there, it continues to drop for some time, not too much, but between 3 and 5 hours it drops to 0

 

That's ok.
You checked the injectors for leaking, also if they have a uniform spray pattern?

 

I checked everything directly on the branch on the car and on the machine... I began to suspect the engine ECU or the engine head that it was not the valve... after I measured the engine compression on a cold engine and it showed 8 bar per cylinder.. .maybe not ideal but it is enough to work....