The list price of a sender unit is $340, so when my fuel level gauge stopped working, I was not very happy. I bought a portable 2 gallon tank and kept it full of fuel in the trunk of the car in case I ran out unexpectedly and I figured I would just leave it broke. That wasn’t good enough. I like gauges that work, what can I say! Luckily, the German designers of this car made taking the sender out possible without too much trouble. They positioned the box that houses the first-aid kit directly above the sender. It is a simple matter of unscrewing it and sliding it up. When I finally scraped enough gunk off of the bottom of it, I found a funny little nut to remove the inerads out of the protective tube. (looks like the tube also serves to dampen the fluid movement) I cleaned it up and installed it again, and now I have a working fuel gauge again! I think I’ll go ahead and keep that extra 2 gallons of fuel in the trunk though.
A note about what caused this: I left the car sit for about a year without driving it. Diesel fuel is often contaminated with microbes that grow and form nasty dark crystals on all the surfaces. You can buy biocide treatments, but they are not sold in all stores, and are a little hard to find. NAPA had a bottle that I used and hopefully cured my problems. Some diesel owners refuse to fill up at smaller stations because that is where the contaminated fuels usually come from: stations that don’t turn over their fuel supplies quickly.