Ford: 1988 f150 -no fuel to high pressure pump, fuel pressure regulator, dual tanks

Question
My f150 has dual tanks.Both lo pressure pumps appear to be working.Fuel is getting to the black fuel canister mounted on the frame rail between the tanks and the hi pressure pump.No fuel is getting passed the canister to the h.p. pump.Is there a closed valve inside the canister that requires a strong suction from the h.p. pump in order to open it and permit the gas to flow?I don`t know what`s inside the canister.It has 4 fuel lines running to the two tanks .On the other side there are two lines-one to the h.p.pump and I gather the other is a return line from the fuel pressure regulator.I`m guessing.I need to determine how the canister works before replacing what could be a weak or worn out h.p.pump.Any input is most welcome.Thanks.

Answer
Hi

This is the switching valve for the fuel.

When you select a tank to pump from, the pump creates pressure in the line to that valve switching the feed and return lines closed to the other tank and open to the one you selected. fuel then reaches the HP pump and off to the regulator. excess fuel is rerturned to the same tank.

Often the valve may fail, sending excess fuel back to the wrong tank, but I suspect that because you cannot get fuel from either tank and you say that all 3 pumps are working, that you may have an older style with a filter in the round screw off base. Remove this filter and throw it away.