One problem related to fuel pump has been reported for the 2008 Mercedes Benz E350. The most recently reported issues are listed below.
I own a 2008 mercedes E350 4matic. After a trip, with the car sitting at the airport for a week in warm weather, I entered the car and noticed a strong gasoline odor. I vented the car and drove home. The odor remained. Subsequently I had the car put on a lift and there was a stain coming down around the sides of the gas tank. I also removed the rear seat and noticed that the seat foam was saturated with a gasoline smell directly above the access panel for what I believe is the fuel pump assembly. I understand from local mechanics that this may be a frequent occurrence with mb e series cars. This leads to a very dangerous situation in terms of potential fire/explosion as well as excessive evaporative emissions. Mb USA stated that they do not have an active recall campaign for this problem.