The fuel pumps weep due to age.
Have a look at my photo documentary on replacing:
1. Fuel pumps (2)
2. Fuel filter
3. Fuel accumulator
4. Hangers for assembly
5. 2 main fuel hoses
190E Fuel Pump Replacement - a set on Flickr
Replacing fuel pumps, fuel accumulator and hangers (pics) - Mercedes-Benz Forum