A 1992 Mercury Sable doesn't have a readily accessible, easily-located fuel pump cutoff switch like some vehicles. There's no single switch you can just flip to shut off the fuel pump. The fuel pump is controlled by the vehicle's computer system and various safety interlocks. Shutting off the ignition is the primary way to stop fuel flow.
To completely disable the fuel pump, you'd need to disconnect the electrical connector at the fuel pump itself (located in the fuel tank, requiring dropping the tank) or disconnect the power to the fuel pump relay. Both of these are advanced procedures and should only be done by someone experienced with automotive repair.
