The dealership is having major problems fixing my fuel pump. This time is the 3rd time in 2 months, 4th in a year, that my ML is in the shop for the fuel pump. The manager tells me each time that they put a new one in and this won't happen again. Well the first 2 times I believed them because I figured since I am not paying for it, it must really be fixed. Can someone give me any advise on what I might tell the dealership to fix since they obviously don't know what to do.

A very common fault of those pumps is too over heat and it actually fries the harness at the pump. have them do a thorough check of the electrical connector at the pump and also do an amp draw test of the new fuel pump. If the new fuel pump draws 9.0 amps or more, you may have wiring problem. They shouldn't charge you more than half an hour to check the draw. Also put in a new relay.
Fuel pump issues are very common on those vehicles, but the later pumps are much better than the originals. There's no good reason to be back in there four times in one year........

Fuel contanimation is the MOST likely cause....the 1998-99 ML's had that problem from the factory...we tried every thing BUT only a fuel tank was the solution!

WE installed at least 40-50 tanks in those trucks....

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Do you think that the fuel pump is bad? How much does a new fuel tank cost? What should I have the dealership replace (fuel pump, fuel tank, etc)?

Since the tank can't be drained OR cleaned once the fuel is contaminated it stays that way.... JUST keeps killing fuel pumps..we installed ALL of those tanks DUE to repeated fuel pump replacements!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

DOC, besides the obvious, is there a good tell tale sign when it is contaminated? We don't have a good fuel test kit here. If I don't see anything abnormal in the tank and the smell/color of the fuel appears normal, is there something obvious to check?

Thanks...I'll relay your thoughts to the dearlership.