If you need to shut off the fuel supply for safety reasons (e.g., fire), you'll need to disconnect the fuel pump's electrical connector or the fuel pump relay. This requires some mechanical knowledge and access to the vehicle's electrical system under the hood. Consult a repair manual specific to your 1998 Cadillac Seville to locate these components safely. Improperly working with the fuel system can be dangerous due to the potential for fire or fuel leaks.