SYSTEM / Hydraulic System Neutral Circuit When the control lever is in neutral, pressure oil from the main pump passes through the control valve and returns to the hydraulic oil tank. Single Operation Circuit Pressure oil from main pump 1 is routed to the 4-spool control valve and is further routed to each spool of the travel (right), bucket, boom 1 and arm 2. Pressure oil from main pump 2 is routed to the 5-spool control valve and is further routed to each spool of the swing, arm 1, boom 2, auxiliary and travel (left). The boom and arm are actuated by pressure oil from two main pumps. Pressure oil from each main pump is combined and supplied together. T2-4-16