One problem related to fuel pump has been reported for the 2000 Mercedes Benz M Class. The most recently reported issues are listed below.
This is experienced by most of the ml drivers: while driving the car, the car just stops and here is what mercedes said and what happens according to mb research: the gas inside some underground tanks dissolves the protective liner. The liner ends up as a gooey substance in our tanks. As long as the pump is running there is no problem. After shutting down, the substance hardens inside the pump and freezes it. Have someone hit the bottom of the tank with a big hammer while someone else is starting up at the same time and most likely you'll get the vehicle running again - then drive to the dealer as soon as possible to get the pump replaced. Frozen pumps sent for evaluation to stuttgart did work when they arrived there without the presence of gas the "glue" had hardened to a point that it got brittle and the pumps worked again.