Originally Posted by Tbone

I am not a mechanic, but have a theory that seems to work for biodiedel and sticky fuel gauges. I have three early 80's MB and have run them on Biodeisel for the last 12 months. All developed a new symptom of sticky "wacky" fuel gauge past 1/4 full within 3 months of each other. On the first one I replaced the sending unit for lack of anything better to try. It worked. When the second started I became suspicious. So at low fuel tank levels I added a good diesel stabilzer (PRI-D) which has been a good one for me. Then added a tank full of B20 and no more probelems. My theory is that the B20 I switched to was dissolviong lots of old petrodiesel debris from the system and pressumably being lighter, it floating to the top of the fuel. As the tank fuel level dropped to use the last of the fuel, the stuff temporarily clogged something in the sending unit. The additive seemed to purged this stuff some way and now I am not having problems. A $15 bottle of PRI-D beats new sending units if the result is the same. I don't think it can hurt to try it. There is also a PRI-G for gasoline as well as PRI-D for diesel engines.

T-bone
84 300sd
84 300D
83 240D manual