To me, the logical way of reading a low value (x-240ohm) tank sender is this:
560ohm resistor from the 3.3volt pin to the sender. Other sender connector to ground.
The sender now produces ~0-1volt that can be read with 1.1volt Aref enabled.
Translate the A/D values to liters/gallons/whatever with a lookup table (if your tank has an odd shape).
Leo..