* Disconnecting the fuel pump relay: This is the safest and recommended method. Locating the fuel pump relay in the under-hood fuse box (often labelled, though sometimes requires a diagram) will allow you to remove the relay and interrupt the power supply.
* Disconnecting the fuel pump inertia switch: Some 1989 Mustangs may have an inertia switch (a safety device that cuts power to the fuel pump in a collision) located in the passenger compartment. This can interrupt the fuel flow, but it's a less reliable way to shut the system down for routine maintenance or emergencies. The switch may reset automatically.
Important Note: Disconnecting power to the fuel pump is not an immediate shutoff. There will be residual fuel in the fuel lines and injector rails. Do not attempt this unless the vehicle is parked and the engine is off.
Consult your owner's manual for the precise location of the fuse box and relay. You may also find diagrams online by searching for "1989 Ford Mustang fuse box diagram" or "1989 Ford Mustang fuel pump relay location."
