Fuel Selector Valve- Diagnosis/Replacement: Overview
83ford6Article No. 83-22-21
FUEL SYSTEM - (7.5L) - FUEL SELECTOR VALVE DIAGNOSIS
LIGHT TRUCKS 1983/84 ECONOLINE AND F SERIES
Testing of warranty returned fuel selector valves used on 1983/84 Econoline and F Series vehicles with the 7.5L engine indicates that selector valves are being replaced unnecessarily. The procedure listed below should be followed when a selector valve concern is suspected. Use of this procedure will eliminate unnecessary selector valve replacement.
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 and then 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 or the motorized fuel 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 valve to actuate opening the ports to the front tank and allowing fuel to flow through the fuel line to the engine.
When the fuel tank selector switch is moved to the rear tank position, power is supplied from the selector switch to terminal number 1 of the motorized fuel valve. The ground path is completed through terminal number 2 of the fuel valve and is grounded through the selector switch. This current path causes the valve to actuate opening the ports to the rear tank and allowing fuel to flow through the fuel line to the engine. The valve also directs excess fuel which is returning from the engine to the same tank that fuel is being pumped. Fuel valve terminals 3 and 5 are connected to front fuel tank sender and the rear fuel tank sender respectively. Terminal 4 feeds the fuel gage. In the front tank mode an internal switch connects terminal 3 to terminal 4 thus supplying the front tank sender signal to the fuel gage. Terminals 3 and 5 are connected in the rear tank mode.
Power is sourced to the chosen tank electric fuel pump by the fuel pump selector relay. Terminal number 2 of this relay is electrically connected to terminal number 2 on the fuel tank selector switch. (This causes the front
pump to run only when the front tank is selected and the rear pump to run only when the rear tank is selected). Relay terminal number 1 is connected to ground to complete the relay coil circuit. Relay terminal number 4 supplies power to the front tank pump and terminal number 5 supplies power to the rear tank pump.
The input power to selector relay terminal number 3 is provided by two sources: direct from the starter solenoid during the crank mode only, or through a 0.75 ohm resistance wire connected to terminal number 3 of the fuel pump cutoff relay. The resistance wire reduces slightly the voltage supplied to the in tank pump during normal operation. The fuel pump cutoff relay coil receives its power through terminal number 2 from an engine activated oil pressure switch which is closed only when the engine is running and the relay coil is grounded through terminal number 1. Power to run the fuel pumps is supplied through an inertia switch to terminal number 4 of the fuel pump cutoff relay.
OTHER APPLICABLE ARTICLES: None
WARRANTY STATUS: "INFORMATION ONLY"