I have a w163 ML 270 CDI of 2001 at 250,000 km. Recently, occasionally has started to do the following: the car will start/crank normally, then after e few seconds it dies. After this, it needs long cranking to start. Can not tell if it is related to engine temperature since it happens on both occasions. I have already changed the set of o-rings in the fuel system. Any suggestions about the cause?