TM   5-3805-258-24-1 H  Y  D  R  A  U  L  I  C   S  Y  S  T  E M S  Y  S  T  E  M  S   O  P  E  R  A  T  I  O N DUMP  Operation When the tilt control lever is moved to DUMP position, dump stem (11) moves to DUMP position. There is no detent for this position. Pilot oil is now free to go through lift and tilt pilot valve (5) to the right end of tilt valve spool (13). The tilt valve spool moves to the left. The pilot oil at the left end of tilt valve spool (13) goes back to tilt back stem (12) and on  to  hydraulic  tank  (18). The movement of tilt valve spool (13) stops the flow of oil through lift and tilt control valve (26). Implement pump pressure increases and opens load check valve (9). The oil from implement pump sec- tion (27) now goes to the rod end of tilt cylinder (1) and causes the cylinder piston and rod to retract. The Z-bar linkage causes the bucket to dump. The move- ment of the cylinder piston and rod pushes the oil out of the head end of the tilt cylinder. This oil comes into lift and tilt control valve (26) and goes around both valve spools (13) and (22) on its way back to oil filters   (29)   and   hydraulic   tank   (18). When the tilt control lever is released, the lever and dump stem (11) go back to HOLD position. The flow of pilot oil through lift and tilt pilot valve (5) is stopped. The springs on tilt valve spool (13) move the valve spool back to HOLD position. The pilot oil at the right end of the tilt valve spool goes back to dump stem (11) and on to hydraulic tank (18). The implement oil in tilt cylinder (1) is held by tilt valve spool (13) and movement of the cylinder piston and rod stops. The bucket is held in the dumped position until the tilt control lever is moved again. DUMP Operation With Engine Off When the lift arms are raised, the bucket can be dumped with the engine off. The pilot oil supply comes from the head end of the lift cylinders. This oil goes through check valve (14) to selector and pres- sure control valve (10) which decreases the pressure of the oil to approximately 1030 kPa (150 psi). The oil then goes to lift and tilt pilot valve (5). When the tilt control lever is moved to DUMP position, dump stem (11) moves to DUMP position. The oil goes to tilt valve spool (13) and moves it to DUMP position. The head end of tilt cylinder (1) is now open to hydraulic tank (18). Make-up valve (8) opens so that the rod end of tilt cylinder (1) is also open to hydrau- lic tank (18). The weight of the bucket causes the bucket to dump. LIFT  CIRCUIT RAISE Operation When the engine is running with the control levers in HOLD position, pilot pump section (19) takes oil from hydraulic tank (18) and sends it first to pilot section relief  valve  (17)  which  controls  the  maximum  pressure in  the  pilot  system.  The  pilot  oil  flow  then  divides.  Some oil goes through line (16) to the hand metering unit of the steering system. Some oil goes through check valve (15) and selector and pressure control valve (10) to lift and  tilt  pilot  valve  (5).  The  valve  stems  in  the  pilot  valve stop the flow of oil in HOLD position. The oil from pilot pump  section  (19)  goes  through  pilot  section  relief valve (17) through oil filters (29) and back into hydrau- lic tank (18). At  the  same  time,  steering  pump  section  (20) sends oil through line (23) to the steering control valve of the steering system. Also, implement pump section (27) sends oil to main relief valve (4) which controls the maximum pressure in the implement oil system. The oil then goes through lift and tilt control valve (26) because both valve spools are in HOLD position. The oil then goes through oil filters (29) and back  into  hydraulic  tank  (18). When the lift control lever is moved to RAISE de- tent position, lift stem (7) moves to RAISE position. Pilot oil is now free to go through lift and tilt pilot valve (5) to the left end of lift valve spool (22). This causes the lift valve spool to move to the right. The pilot oil at the right end of lift valve spool (22) goes back to lower stem (6) and on to hydraulic tank (18). The movement of lift valve spool (22) stops the flow of oil through lift and tilt control valve (26). Implement pump pressure increases and opens load check valve (25). The oil from implement pump section (27) now goes to the head end of lift cylinders (21) and causes the cylinder pistons and rods to extend. The lift arms cause the bucket to lift. The movement of the cylinder pistons and rods pushes the oil out of the rod end of the lift cylinders. This oil comes into lift and tilt control valve (26) and goes around lift valve spool (22) on its way back to oil filters (29) and hydraulic tank (18). When the lift control lever is moved out of RAISE detent position (either manually or by the lift kickout mechanism), the lever and lift stem (7) go back to HOLD position. The flow of pilot oil through lift and tilt pilot valve (5) is stopped. The springs on lift valve spool (22) move the valve spool back to HOLD posi- 3-112