The lock cylinder is the "knob" for the switch. If it turns to "ON" position and back to "off" position, with the key, that's all it is supposed to do. It operates an actual electrical switch. The ignition switch. The switch allows power to be supplied to the coil and other components. When it cuts power to the coil, the motor stops. So you have been replacing the wrong component and/or you have other electrical wiring/ignition problems.
We ALWAYS need the Truck year, make, model. The motor year, make, model. On EVERY new post.
