I was told the best way to clean the fuel system on a diesel Mercedes is by running a can on Llbro-Moly Diesel Purge through the fuel system. It has directions, however, I am not clear on where the fuel pipe is between the fuel tank and fuel pump? Also where is the fuel return pipe? My car is a 95' S350. Pictures would be most helpful to me? Also, how often is the timing chain to be replaced on this car? When cold, just started the motor is a lot louder than when warm? What causes this? I know diesels make different noises when running, but can you here something very different when a timing chain gets loose? Once this motor is warm, you can barely hear is run. Thanks!