Originally Posted by bluesman2333
When the tank selector is in rear, fuel returns to the rear tank as expected. When the front tank is selected, it slowly fills up the rear tank but may be also returning to the front tank. My question is that since I don't see a valve under the truck, the in tank fuel pump must have a valve in it that selects the return meaning that the rear tank valve is stuck open. Correct? Is there a way to repair this or is it a fuel pump replacement project?
Yes you have a bad check valve or shuttle valve inside your rear FDM (Fuel Delivery Module) that is inside your rear fuel tank. The pump is also inside the FDM.
EDIT:
On a 1993 you need to check the FPR (Fuel Pressure Regulator) also as they had a lot of bad ones that year and the FPR will take out these valves.