I am assuming you have a problem with the fuel tank readings on this? Now I am not an auto-electrictrian and would not take on this sort of job, but I do like a dabble now and then. When I have something like this, I prefer to go for voltages because this proves both outputs and resistances. I have no idea what the voltage should be, but I would probably either scope or measure the voltage whilst moving the sender sensor and see a smooth changing reading.
Now, I may be way off the mark on this and I am sure a more qualified tech will come along soon and put us both right.