This, I'd say, is a good example of where you should do things in steps.
I'd start with a sketch doing nothing but reading the pin where the float's connected and writing its value to the monitor.
That way, I'd know that the float is connected correctly and that I'm reading it properly. Then later when I add three libraries and other cr@p, if it doesn't work I can reasonably assume that what I just did broke it, and I can back the changes out until it works again.