SL-Class (R129) 1990-2002: SL 280, SL 300, SL 320, SL 500, SL 600, SL 60 AMG

SL/R129: Fuel Gauge Help

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Old Jul 2, 2008 | 11:36 PM
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Question Fuel Gauge Help

This is the second time in a row I have encountered this minor discrepancy. Car is reading empty, yet when I fill it up, it takes roughly 16.5 gallons to fill it. Now, the reserve is only 2.6 gallons, falling a few short of the 21.1 gallon total capacity of the tank. Additionally, when filled up entirely at the gas station, the gauge reads only 7/8th...after driving maybe a mile or two, it increases to 15/16th of a tank. Usually the needle is pinned on full and stays that way.

I have done a bit of reading on fuel sending units in the past twenty minutes, but all of the cases I have come across have much more drastic discrepancies than mine, which I take as a positive sign. I ran some Techron through the fuel system a few thousand miles ago...maybe time for a bit of Seafoam in there to clean the thing out?

Also, is there a way to test the sending unit before I go out and pick up a new one? Thanks a bunch!
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Old Jul 3, 2008 | 11:57 PM
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Your problem is the fuel tank sending unit, they crap out sometimes when you get a bad tank of gas. I lost one in my M3 and it wasn't that bad to have replaced, $250 or so.
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