My truck keeps shutting off?

I have a 1991 ford F-150 and sometimes when driving the truck will just shut off. It will also happen when I hit a bump. I don't want to have to get rid of the truck as it used to belong to my grandpa.

Sounds like a loose connection in the ignition wiring circuit. You can try replicating the problem by wiggling or pulling various wires for the ignition switch under the dash while the engine is running in Park to see if you can pinpoint where the wires are loose and cause the engine to shutoff… Retighten the connector or replace it or check for other issues where wires may be loose in their connectors. If wiggling those wires doesn't help pinpoint a loose connection, you may have to continue checking all the wiring connections under the dash and under hood to see where one might be loose, corroded, etc… Perhaps pickup up a shop manual like Chilton or Haynes at a parts store so you can trace which color wires are for the ignition circuit. If nothing else, you could wire in new wiring and bypass the old wiring for the ignition to see if that cures the problem. Make sure to check all grounding wires or straps too for being loose or corroded/broken.

Are you scared of mechanics? Go find one. The truck is a Ford, not a "ford." Please capitalize proper names of brands of cars. Your name also must be capitalized. Please do so.

Sounds like it could be the ignition switch! If the ignition switch is worn too much it can shut the engine down! Also if the coil is getting too hot it can shut the engine down too!