I am currently driving a S320 220. Recently, i have this werid starting problem with my car. When i crank the vehicle, the engine will cranks for about 10 seconds prior to starting. It seems like the fuel pump is trying to build up pressure. I had the fuel rail pressure checked and it seems like it can't hold any pressure after the engine is turned off. Was recommended that to have the fuel filter changed, but still no improvement. Can anyone shed some light on this issue? I heard that there is an integrated pressure regulator in the filter. Just wondering whether i am given the correct filter.

 

yes.
fuel pressure regulator is integrated in the filter.
if the problem exist before and after replacing the filter, then it's not the filter.
the pressure build-up is immediate.
check fuel pump delivery rate (e.g. 2 liters in 1 minute).
check for fault code.
check for restriction in fuel line.

 

sounds like it could be one of these in this order, crank sensor, airmass, and cam sensor

 

I am pretty sure the check valve for the fuel system is in the fuel pump. i would try that next.