Abstract: A hydraulic power unit for controlling a work unit includes a reservoir for storing hydraulic fluid, a hydraulic pump for moving fluid from the reservoir, a prime mover for driving the hydraulic pump, and a manifold for controlling flow between the work unit, pump and reservoir. The manifold includes a spool valve assembly with a spool that is translatable within a spool bore to provide this control. The spool bore is fluidly connected to the work unit via a pair of work passages, to the hydraulic pump via a pair of supply passages, and to the reservoir via a return passage. The manifold is configured to direct fluid flow received from the work unit at either of the work passages to the reservoir while bypassing the pump by preventing fluid flow through the spool bore in a direction from either of the work passages to either of the supply passages.