Bypassing the rear fuel tank

Removal and Installation

1. NOTE: Make sure fuel tank (9002) is properly supported during removal and installation procedures.
   Drain fuel from fuel tank .

1. Loosen fuel tank filler pipe clamp.

1. Remove fuel tank heat shield (9A032) from vehicle.

1. Support fuel tank .

1. Remove bolt from rear fuel tank support strap (9092) and remove rear fuel tank support strap .

1. Remove bolt from front fuel tank support strap and remove front fuel tank support strap .

1. Partially lower fuel tank to gain access and remove feed and return lines from sender ports. To disconnect push connect fittings, refer to Push Connect Fittings in this section.

1. Remove electrical connector from sender unit.

1. Remove fuel vapor hose from evaporative emission valve (9B593) .

1. Lower fuel tank from vehicle.

You have 2 problems. First is, the leak, fix it. Second is the actuator / fuel solenoid on the frame is bad also. You shouldn't get fuel to the other tank when you switch from front to back.

did you check to see if your gas cap is missing?

Use compression barb fittings on the pressure side with fuel injection line NOT REGULAR FUEL HOSE THE REGULAR HOSE WONT HOLD UP TO THE PRESSURE. The return line can be regular fuel line because of the low pressure.

WHERE IS FUEL LEAKING OUT FRONT OR REAR OF VECHICLE DONT CRANK OR DRIVE VECHICLE UNTIL LEAK FIX.LEAK AT FRONT IS A FUEL LINE AT FUEL RAIL TO PRESSURE REGULATOR.OR LEAK AT THE REAR CAR COULD BE LEAKING FUEL LINE AT FUEL TANK OR HOLE IN THE FUEL TANK..

Ok sounds like a electrical problem being an 89 its fuel injected eather 5.0 or 5.8 each tank has its own fuel pump and sending unit a dashboard switch, relay, fuse and switching motor. check your fuel line from the front tank it could be clogged. check for 12v pwr. to the front pump the sending unit will require 4V but not much. as soon as the fuel rail pressureizes the ECM shuts the pump off using the relay. Usually the tank switch goes bad first.

Hi:
Your vehicle only has one set of connections to the heating system, and you disconnected them when you bypassed the heater core. There is not a seperate heater core for the rear heat, just ducts off of the front heat.

The leaking from one tank to another was covered by a recall from Ford. Not sure if they still foot the bill for installation of the required check valves. These are still available from the dealership. The rear one is the hardest to install. The check valve can be installed without pulling the rear tank. As for your front sender I would clean all of the connections to the sender and make sure it has a decent ground. If it still only reads at the 1/4 tank level you will have to replace the sender to rectify the problem.

I have to say i'm only guessing, but it sounds like the valve that switches the flow of gas from one tank to the other must be sticking part way open, or bypassing or something, and anything your engine doesn't require, is being returned to the front tank, instead of the rear.

Have the same problem, its the switch valve, not sure how to fix it yet. But i can tell you thats what it is.