Fuel Gauge not working: 1990 190E
 

I recently purchased a 1990 190E from an elderly gentleman, and the fuel gauge has never worked.
Fuse #9 was changed, as recommended in other posts here, along with a few other fuses. Every other gauge on the dash works as normal. There are 186K miles on the car, and I've put on 3k miles, averaging 18mpg, if that makes a difference. Thanks in advance!

I was off on my mpg estimation, it's closer to 23MPG.
Is there anything I should check regarding the fuel gauge not working, aside from the fuse which was already changed?