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Home >> Ford >> 1986 >> Bronco II RWD, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Fuel Selector Valve - Electric >> Testing >> 7.5L Engine

7.5L Engine

  1. Turn ignition switch to "ON" position. With valve in "FRONT" mode. Disconnect selector valve connector. Check for voltage between connector terminal 2 and ground. If voltage is present, go to step 3.
  2. If no voltage is present, check voltage across fuse at fuse block. If fuse is blown, check selector valve circuit for shorts. Repair shorts, replace fuse and repeat step 1. If fuse is okay, go to step 6.
  3. Check for voltage between selector valve connector terminals 2 and 1. If voltage is present, go to step 4. If no voltage is present, check for open ground circuit from valve connector, through selector switch to ground. If circuit is okay, go to step 6. If not okay, repair ground circuit, repeat test.
  4. Place switch in "REAR" position, and check for voltage between connector terminal 1 and ground. If voltage is present, go to step 5. If no voltage is present, go to step 6.
  5. Check for voltage between selector valve connector terminal 1 and 2. If voltage is present, go to step 8. If no voltage is present, check for open ground circuit from valve connector, through selector switch to ground. If circuit is okay, go to step 6. If not okay, repair ground circuit, and repeat step 3.
  6. Remove selector switch from instrument panel and disconnect switch from harness. With switch in "FRONT" position, check for continuity between terminals 2 and 4, and between terminals 1 and 3.
  7. Place switch in "REAR" position and check for continuity between terminals 1 and 4, and between terminals 2 and 3. If switch is okay, go to step 10. If switch is not okay, replace switch.
    NOTE: Selector valve will make a "zip" sound when shifting from one mode to another.
  8. Using a jumper wire, connect selector valve terminal 2 to battery positive post. Using a second jumper wire, connect terminal 1 to ground. If valve is in "FRONT" mode, nothing will occur. Reverse jumper wires. Valve should shift to "REAR" mode.
  9. Reverse jumper wires once more. Valve should shift to "FRONT" mode. If valve shifts into both modes, go to step 12. If valve does not shift into both modes, replace fuel selector valve.
  10. On "E" series, check continuity of Brown/Orange wire (circuit 808) and Red/Yellow wire (circuit 739) between selector switch and selector valve. On "F" series, check continuity of Brown/White wire (circuit 674) and Orange wire (circuit 974) between selector switch and selector valve.
  11. If continuity between selector switch and selector valve is okay, go to step 12. If continuity between selector switch and selector valve is not okay, repair open circuits as necessary.
  12. Remove connector from oil pressure switch and insert temporary shorting wire between 2 connector terminals. Pinch off fuel line between rear tank and selector valve. Remove fuel hose to carburetor, and place end of fuel hose into a container.
    NOTE: Fuel pump volume is approximately 1/2 gallon/minute.
  13. Turn ignition switch to "RUN" position. Place switch in "FRONT" position. Check for a solid, continuous fuel flow. If fuel flow is not okay, go to step 14. If fuel flow is okay, remove clamping tool from rear supply line, and go to step 18.
  14. Disconnect supply hose to engine at selector valve. Disconnect supply hose from front tank at selector valve. Connect 2 hoses together using a length of fuel line. Repeat steps 12 and 13. If fuel flow is okay, replace fuel selector valve.
  15. If fuel flow is not okay, check front fuel tank sender, fuel lines and fuel filter for restrictions. If restrictions are found, clean, repair or replace components as necessary and repeat steps 12 and 13.
  16. If lines, filter and sender are okay, remove front fuel tank sender connector. Connect a 12-volt test lamp to pump terminal and to ground terminal of sender connector.
  17. With ignition switch in "RUN" position and with switch in "FRONT" position, test lamp should light continuously and should go out as soon as rear tank is selected. Check fuel pump. If fuel pump is okay, continue test.
  18. Remove connector from oil pressure switch and insert temporary shorting wire between 2 connector terminals. Pinch off fuel line between front tank and selector valve. Remove fuel hose to carburetor, and place end of fuel hose into a container.
  19. Turn ignition switch to "RUN" position and place switch in "REAR" position. Check for a solid, continuous flow of fuel. If fuel flow is not okay, go to step 20. If fuel flow is okay, selector valve is operating properly.
  20. Disconnect supply hose to engine at selector valve. Disconnect supply hose from rear tank at selector valve. Connect 2 hoses together using a length of fuel line. Repeat steps 18 and 19.
  21. If fuel flow is okay, replace fuel selector valve. If fuel flow is not okay, remove rear fuel tank sender connector. Connect a 12-volt test lamp to pump terminal and to ground terminal of sender connector.
  22. With ignition switch in "RUN" position and with switch in "REAR" position, test lamp should light continuously and should go out as soon as front tank is selected. Check fuel pump. If fuel pump is okay, fuel supply system is okay.
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