The tank certainly is not full. 280 miles on 8 gallons would be 35mpg which is how-you-say-in-your-language impossible.

Fuel tank senders have been a problem for some time now and in fact a friend's '99 CLK430's sender failed in the car's first year. My W203's senders were replaced early in the game also.

The senders are on the tops of the tanks. Fold up the rear cushion, lift off the carpet and there it is. Takes a special tool to unscrew it from the tank, unfortunately.

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Roger E.