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........

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

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....

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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?

We couldn't even see any contamination in the fuel tanks on those early ML's, but MBUSI in Vance Alabama assured us that that was the problem & that their MAIN tanks were the problem..

Sugar OR other contaminates will not be seen BUT a local fuel distributor can check for those problems.

__________________
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

Sorry for my misunderstanding...but are you saying that I should have the fuel pump, fuel tank, and all the electrical components replaced? Is this gonna be like a $2K job?

I'd definitly get the amp draw test done FIRST. It should take them all of 20 minumtes to check that. Makes sure they check it with the engine up to operating temp. I've had several pumps that when started drew around 6 amps, and then after a while the amperage would climb above 10 amps= BAD. So it's not always immediatly obvious.
And money wise, it's probably cheaper to have a fuel sample sent out before throwing a fuel tank at it. Like DOC said, they couldn't even see the contamination.

DUH, forgot to ask what your original symptom was. Why do they keep throwing fuel pumps in?

will do...thanks you guys are a big help

When trying to start it, it just goes vrrrrvrrrrvrrrr. Happens about a week or so after I get it back from the dealership. This last time, it happened the day after I put gas into it.

Well...the fuel was tested, amps to the pump as well. Nothing abnormal found. The dealership has sent a request for help to the school house. Hopefully they get the answer to fix this. Any thoughts from you guys??

Not amps "to" the pump. that could be mis-understood as power to the pump.
Need meaurement of amp draw OF the pump when running, ESPECIALLY when engine is hot and vehicle has idled for a while.

When does the car not start? When hot, after sitting overnight? Does it die while driving? Does it die at idle......