A couple of thing you could check.
1) Can the float move up and down freely.
2) When tank is empty the float should be at the lowest point and water should be getting into the tank.
3) Press the float down and see how much water is getting into the tank.
4) If very little water is getting into the tank. You should allow more water into the system from the external source.
5) You may have to open the nozzle of the inlet. Some particles may be obstructing it.
Hope that helps!
@ma
December 2008