I never had that issue. Are you sure you are matching them up exactly?
However - it may be the particular brand of valve...?
The individual tank "send" and "return" lines must be matched from the front of the valve - to the back of the valve. There should be 4 ports / lines on the back of the valve and 2 ports / lines on the front.
The 2 on the front go to the motor (fuel pump and return - not sure of which is which...)
From my memory - I can't remember which of the 4 ports goes to which line on the back - (front tank suction and return - - back tank suction and return.
2 each - Stock - 97 F-350 7.3 PS 1 ton Duallys - RWD - AT
Last edited by Audiowriter; 04-15-2019 at 04:30 AM.