ML320 suddenly stops
 

i have an ML320 2002. the car suddenly stops while driving on the road and sometimes it would take too much tries to restart, the mercedez service center and they don't know what is the problem. they said it might be the control unit.

please note that before they said it's the airmass control and i replaced it, the car millage is only 30,000 km's

does it eventually restart? if so how long does it take? i perconally would suspect a fuel pump failing or a crank position sensor. is your mercedes service center an authorized center? sounds like they are not too good with diagnostics.

it did restart multiple times after it went of on the road, then when i slowed down it went off and didn't start, i had to get a truck to take it to the service center, the service center is the only autherized agent for mercedes in the country, but it looks like they haven't face such a problem,, it has been 2 days since they got the car and they couldn't find the problem untill now, they replace a part and they turn the car on, but it wents down after 10 minutes or so

Sounds like the CPS to me; and if it is, it doesn't throw any codes.

Cheap fix.

Ditto!
Most likely the flywheel crank sensor.

If its a CDI, M-B has a recall in the works for failed crank sensor that causes this exact problem (my service rep told me about it). symptoms: engine stops for no apparent reason and will not start. No 'limp home' or anything!

The crank sensor was replaced and the car was normal for the full day, the next day they tried starting the car and it did not start, they tried several times and then it started. The problem remains and they said the computer isn’t presenting any errors, they said now is that the problem is from the control unit, although I’m not supporting that conclusion, the control unit won’t be failing sometimes, if it is defected it wont start at all, they said I should keep the car at the workshop so they could check all the sensor. Please note the car mileage is 30000km and there was no case of humidity or washing the car. Could you please assist and if it was the control unit they say it would cost me about 2500 dollars. They say the control unit should be ordered through them because it has the chassis number of car!!

Diagnosis would start when the engine ISN'T running.
With a scanner connected they should check for a RPM signal when operating the starter.

IF there isn't a RPM reading in live data then either the new sensor is bad OR the wiring at the sensor has a problem.

If the RPM signal IS there possibly the fuel pump OR relay is defective.

do you have the part number of the unit that was replaced? it is possible they may have replaced the wrong sensor.

Let's not forget about the Camshaft Position Sensor! This is another part known to fail without storing any fault codes. Sometimes, a bad cam sensor will actually throw a fault code for the Crank Sensor!. I've seen this happen many times.

The most obvious difference in the way these two parts fail is in the actual symptom. A bad crank sensor can cause an engine to stall without warning, or, simply crank but not start. A faulty cam sensor won't cause the engine to stall, but it will cause the crank/no-start condition.

i was kinda leaning toward that also, that was why i wanted to know which part was replaced

cONTROL UNIT
 

they are suspecting that the Control Unit isn't working, the car mileage is 30000KM for god sake......do you believe that!!!