Put a pressure gauge on the fuel rail and see what you get.

If nothing, put an incandescent test light across the fuel pump terminals and see if it lights.

Jumper the fuel pump relay ( should be green relay in the trunk, next to fuse block ) and see if you have light on / pump running / pressure.

Next, pull the hose from tank to pump and see if fuel comes out. The C class tends to corrode the level sending units giving improper level reading. There are two sending units on this car due to the 2 sump tank. These sending units are accessible from the bottom of the tank.