There isn't a readily accessible, easily identifiable "fuel cutoff switch" like you might find on some modern vehicles or equipment on a 1989 Ford F-150. The primary way to stop fuel flow to the engine in that era is by turning the ignition key to the "off" position. This shuts off the power to the fuel pump.
While some aftermarket fuel cutoff switches *could* have been added by a previous owner, they wouldn't be standard equipment. If you're looking for one, you'd have to check for it manually – under the hood, in the cab, or potentially even hidden in the vehicle's wiring. There's no guaranteed location.
