found some explaination in the DIY session
posted by member 'trex92'
"fuel cut switch works like the above mainpower switch. In our cars, we have a fuel pump, which functions are to pump the fuel from the fuel tank to the engine fuel lines so that fuel can reach the engine for combustion (thru fuel injector for EFI cars or carburetor for non EFI cars). The fuel pump needs also electricity to work, so a switch can added to the power wire for the fuel pump to disable the fuel pump. The feature of this fuel cut switch is that you would be able to crank the engine but the engine would not start as got no fuel supply. Most immobilisers uses the fuel cut as one of the forms of immobilising the car."