Were is the fuel cut off switch at on a 1993 ford e-150 5.0 eng Econoline van?

There isn't a readily accessible, single "fuel cutoff switch" like you might find on some other vehicles on a 1993 Ford E-150 Econoline van with a 5.0L engine. The fuel system relies on the ignition system and other safety mechanisms to control fuel flow. To stop the fuel flow, you'd need to either:

* Turn the ignition off: This is the primary way to stop fuel flow. The ignition switch controls the power to the fuel pump relay.

* Disconnect the fuel pump relay: This is more involved and requires locating the relay (usually in the underhood fuse box) and pulling it. This will cut power to the fuel pump, preventing fuel flow. You'll need a wiring diagram or owner's manual to identify the correct relay.

* Disconnect the fuel pump's power wire at the pump itself (Advanced and not recommended): This is dangerous and requires working under the vehicle, potentially with fuel lines under pressure. Unless you're an experienced mechanic, *do not attempt this*.

In short, there is no easily accessible switch. Turning the ignition off is the safest and most reliable method to stop the fuel supply.