A solenoid direct-acting three-position spring-centered directional control valve is used in a hydraulic system to control a linear actuator. When the remote push button is depressed to extend the actuator it fails to move, even though the pump is in operation. Which of the following statements represents the cause?

Correct Answer: Option D — Any one of the above will cause the actuator to not move.

A hydraulic system failure can stem from various points in the power transmission chain. A damaged pump coupling prevents fluid flow, a jammed spool prevents directional control, and an open solenoid coil prevents electrical actuation. Any of these conditions will result in the linear actuator failing to move as commanded.