42 is connected through valve 58 to the left hand side of the cylinder 51 of pump motor 44 through line 64 with valve 58 in the state 60 the left hand sides of the cylinders 55 57 of motor pumps 46 48 are connected through lines 68 70 and valve 58 to the low pressure accumulator 41 these actions cause piston 50 to move rightward forcing fluid from pump motor 44 through line 72 to the right hand side of the cylinder 57 and through line 74 to the right hand side of cylinder 55 in this way the first state of valve 58 causes the fluid control system to move engine pistons 18 20 rightward and engine pistons 24 26 to move leftward from the position shown in fig3 when controller 56 switches valve 58 to the second state 76 high pressure accumulator 42 is connected through line 68 to the left hand side of piston 57 of motor pump 48 and through line 70 to the left hand side of piston 55 of motor pump 46 this forces engine pistons 24 26 rightward when valve 58 is in the second state 76 the low pressure accumulator 41 is connected through valve 58 and line 64 to the left hand side of cylinder 51 of motor pump 44 as pistons 52.