Abstract: Embodiments of the present invention monitor resistance to the movement of the ram and detect one or more injector operation conditions based on that resistance. Some embodiments automatically detect whether a syringe is present in each syringe chamber of an injector based on ram movement resistance so that subsequent steps in the inject process can be automatically initiated or delayed based on the presence or absence of the syringe(s). Other injector operation conditions that can be detected include the injector's syringe sleeve being misaligned for operation, the syringe's wiper being misaligned within the syringe barrel, an occlusion within the syringe, overpressure during injection, and so on. A common way to measure resistance of the ram's movement is how much current is required by the motor driving the ram.