F 250 2WD Pickup V8-7.3L DSL Turbo VIN F (1994)
Fuel Tank Switching Valve: Description and Operation
Fuel Tank Selector Valve
PURPOSE
The fuel selector valve allows the vehicle operator to choose which fuel tank the vehicle operates from. The valve switches between tanks
electrically, controlled by a dash-mounted switch.
OPERATION
The 6-port fuel selector valve is powered by a small electric motor that opens and closes the valve ports. The supply and return ports for either
tank open and close simultaneously.
The valve is shifted to the front mode, connecting the front tank ports to the engine ports, by applying a positive 12 volts to terminal number 2 and
ground to terminal number 1. When the valve reaches the front mode position, an internal switch opens the circuit, stopping the motor.
Switching the valve to the rear mode is accomplished by reversing power: positive 12 volts to terminal number 1 and ground to terminal number 2.
Terminals 3 and 5 connect to the front and rear fuel tank senders respectively, terminal 4 feeding the fuel gauge.
In the front tank mode, an internal switch connects terminals 3 and 4. This supplies the front tank sender signal to the fuel gauge. In the rear tank
mode, terminals 4 and 5 are connected. Therefore, a change in the fuel reading gauge (assuming at least 1/4 tank fuel level difference), means that
the valve has shifted.
Power is supplied to the fuel tank selector switch from the fuse panel when the ignition switch is in the ON position. This power goes through the
fuel tank selector switch directly to the motorized fuel tank selector valve.
With the fuel tank selector switch in the front tank position, power is supplied from the selector switch to terminal number 2 of the fuel selector
valve. The ground path is completed through terminal number 1 of the fuel tank selector valve and is grounded through the selector switch. This
causes the fuel selector valve to rotate internally, opening the ports to the front tank position which allows fuel to flow through the fuel line to the
engine.
With the fuel tank selector switch in the rear tank position, power is supplied from the selector switch to terminal number 1 of the fuel tank
selector valve. The ground path is supplied through terminal number 2 of the fuel tank selector valve, grounding through the selector switch. This
path causes the motorized valve to rotate internally, opening the ports to the rear tank position allowing fuel to flow through the fuel line to the
engine.
