Running the tank is not a good idea as at least will allow air
to enter the fuel pump. Fuel lubricates the fuel pump so by
running the tank dry you are at least taking life off the
pump and creating a potentially explosive situation
(fuel + air + spark from unlubricated DC motor brushes = bang).
Well, that is assuming the the DC motor can spark and I
can think of a couple designs that would separate the spark
from the fuel anyway...

dave