1987 ford f150. has fuel. new fuel pump, filter,and pressure regulator.will

[Tommy]

not pull fuel through the lines?
has duel tanks.

 

[muhlbaierc1]

could be an air leak somewhere in the lines

 

[chevy69]

those are common for the switching mechanism to go out. it is right under the cab and i think its a couple hundred bucks but it is easy to change.