Empty is too high it should read 20 ohms. You simply may have a bad sending unit.

New units are available at MBpartsgiant.com new tank sending unit They are not cheap, or you can try ebay for a used one. Current MB part number is 170 542 15 17. Like I said above Mercedes looses something in the replacement parts from the originals; try another sending unit because the 197 ohms is way off. please read my post #5 and glean the info.

Trying to make a bad unit read correctly just isn't going to work. What you read at empty 197 ohms is not close to the 20 as specified in the service manual. see my post above #5.

Good Luck ~ Keeping these cars running is indeed becoming a challenge.