The 1989 Ford F-150 doesn't have a readily accessible fuel shutoff switch like some modern vehicles. There's no single, easily located switch to instantly cut fuel flow. To stop the fuel supply, you'd need to address the fuel pump relay or disconnect the fuel pump's electrical connection. This usually requires working under the truck.
It's not a simple or easily accessible switch like you might find in other vehicles.
For safety, and to avoid potential damage, if you need to cut fuel flow for any reason it's best to consult a repair manual specific to your 1989 Ford F-150 or seek professional assistance from a mechanic. Improperly disconnecting fuel system components can be dangerous.
