You either have a bad pump or other problems.

Does fuel flow decently after the truck has been sitting for a while, then slow down? If so, it could be an unvented gas cap. Try driving either without the cap or with it loosened.

Otherwise, check the obvious.
Is there gas in the tank?
Is the tank valve open all the way?
If you disconnect the input line to the pump does gas flow freely out the line? If not, check the flow out of the tank, there might be either something in the line or plugging the strainer in the tank.


Fred
52 3600
69 C-10