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Fuel gauge drops to 3/4 after driving 10-20 miles from a full tank

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Fuel gauge drops to 3/4 after driving 10-20 miles from a full tank

 
Old 10-16-2017, 12:22 PM
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18 Model X, 13 GL350, 13 Odyssey, 07 530i
Fuel gauge drops to 3/4 after driving 10-20 miles from a full tank

2004 ML350:

1. Fill up the tank to the max.
2. The fuel gauge shows it full.
3. Drive around 15-20 miles.
4. The fuel gauge shows 3/4 full.
5. Once it drops to 3/4, the gauge works normally.

What should I check?
I put key to ignition position II and removed & plugged back in Fuse 5. But I think this works when the fuel gauge somehow drops to 0 when the tank is full, which is a diff problem.
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Old 10-16-2017, 02:41 PM
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2002 ML 320 & 2006 ML500


This problem usually occurs because of a faulty float which is part of the fuel pump.

Wait until the tank is 1/4 full and remove the fuel pump. Clean the grid with a pencil eraser and reinstall the pump and hope for the best.

Ordering a new locking ring prior to the job is necessary.
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Old 10-16-2017, 03:10 PM
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2015 S550
Agree, I had the exact same thing on my 1999 ML430 and fixed it by replacing fuel pump (which has fuel level float integrated into it).
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Old 10-16-2017, 04:05 PM
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Thank you so much for the info!
I know the opening is under the rear passenger seat.

Does it require a special tool to open up the entry area?
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Old 10-16-2017, 06:04 PM
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I don't recall needing anything special for it. I did reseal it with some caulk to make sure no fumes came out (it had been sealed before). In my model they changed the pump, added a whole additional hose, changed the filter,... so it was much more of a project than just swapping the pump. Hopefully you just have to replace the pump which is easy.

I do recommend running the gas tank fairly low and having a fire extinguisher nearby just to be safe. Lots of gas fumes and the pump is obviously covered in gas when it comes out. I had no problem doing it safely myself but be careful and take your time.
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Old 10-17-2017, 05:56 AM
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2002 ML 320 & 2006 ML500
Here is the procedure.
Attached Files
File Type: pdf
R&I Fuel Pump .pdf (131.5 KB, 54 views)
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