There is no emergency fuel switch on a 1998 Mercury Cougar, or virtually any modern passenger car. Fuel systems are designed with multiple safety features to prevent accidental fuel shutoff and to ensure that fuel delivery stops in a crash. An easily accessible manual shutoff switch is not a standard feature for safety reasons (it could be easily disabled or accidentally turned off).
If you have a fuel-related emergency, your safest course of action is to turn off the ignition and contact emergency services.
