There are two units other than the pump back there - a check valve and the damper. The damper is the one with the screw coming out of it. No need to prime the pump. You don't usually want to run them dry because the fuel lubricates the pump and no fuel destroys it over extended periods. But the second or two required to pull the fule from the tank will not harm the pump. And priming is not needed to draw the fuel up out of the tank. Tom D. Fairfax, VA