A fluid level controlled pumping system includes a pumping unit disposed within
a fluid cavity. The pumping unit includes an inlet operable to receive a fluid
to be pumped from the fluid cavity. The system also includes a valve slidably coupled
to the pumping unit. The valve includes a passage for receiving pumped fluid from
an outlet of the pumping unit. In response to a decreasing fluid level within the
fluid cavity, movement of the valve relative to the pumping unit aligns the passage
with a port of the pumping unit to recirculate the pumped fluid from the outlet
to the inlet.