My recollection was that the turbopump used the engery in the expanding fuel
to pump the fuel. If the fuel runs out doesn't the turbopump stop pumping?

Mike
MU-2

There are a number of differnet ways that turbopumps
on rockets can be powered, what you are describing is an expander cycle,
the SSME is a staged combustion pump.

The pump is preburinign some small amount of fule to spin the turbine,
if I recall it's about 150,000 HP per pump per engine.
This is a lot of power.