Now here is the bottom of the module. It has a circular disk on the bottom.
I am not sure why it is there. It is buoyant and has the 3 channels that you can see. When it is "up" the pump can draw fuel. When it is down fuel cannot be drawn by the pump.
Here is a picture of the picture of the top of this disk. The small rubber tab in the middle goes into the small hole at the bottom of the module.
Here is a side view of the small disk. This is actually from the new module and it is shaped differently than the old one. The old one does not have the 2 different diameters.