Systems Operation

Usage:

Introduction - 914G

Reference: For Specifications with illustrations, make reference to SENR6773, 914G Wheel Loader and IT14G Integrated Toolcarrier, Hydraulic Systems Specifications. If the Specifications in SENR6773 are not the same as in the Systems Operation and the Testing and Adjusting, look at the printing date on the cover of each book. Use the Specification in the book with the latest date.

Hydraulic System Schematic
(1) Ride control accumulators. (2) Ride control solenoid valve. (3) Lift cylinders. (4) Tilt cylinder. (5) Lines to auxiliary cylinders. (6) Dead engine lower valve. (7) Main relief valve. (8) Main control valves group. (9) Line to steering system. (10) Hydraulic pump group. (11) Pilot oil accumulator. (12) Pilot control valves group. (13) Hydraulic oil filters and tank group. (14) Hydraulic oil cooler. (15) Pilot supply line from propulsion charge pump. (16) Hydraulic lockout valve. (17) Return line from propulsion system.

The main components of the bucket hydraulic system are hydraulic oil filters and tank group (13), pump group (10), main relief valve (7), main control valves group (8), hydraulic oil cooler (14), bucket pilot control valves group (12), pilot oil accumulator (11), tilt cylinder (4), lift cylinders (3), auxiliary cylinders (if equipped) and various relief and check valves and lines.

NOTE: For more information on the steering system pump section of pump group (10), see SENR6769, 914G Wheel Loader and IT14G Integrated Toolcarrier, Steering System Specifications and SENR6770, 914G Wheel Loader and IT14G Integrated Toolcarrier, Steering System System Operation, Testing And Adjusting.

Pump Group And Hydraulic Oil Cooler Location
(10) Pump group. (15) Hydraulic oil cooler

Pump group (10) and hydraulic oil cooler (15) are located at the rear of the machine. The oil cooler is located next to the radiator. Access to the oil cooler is gained by raising the engine cover.

Pump group (10) is a two section, gear type pump. The pump group is mounted to the engine on the right side of the machine. Access to the pump group is gained by removing a panel on the right side of the machine.

Main Control Valves, Ride Control Components, Tilt Cylinder And Hydraulic Filters And Tank Group Location
(1) Ride control accumulators. (2) Ride control solenoid valve. (4) Tilt cylinder. (6) Dead engine lower valve. (7) Main relief valve. (8) Main control valves group. (11) Pilot oil accumulator. (13) Hydraulic oil filters and tank group.

Main control valves (8) are located inside the front loader frame. Access is gained by removing a panel on the front of the loader frame.

Tilt cylinder (4) is located on the front end of the machine. Lift cylinders (3) are mounted on the inside on each side of the front frame. Pilot oil accumulator (11) and hydraulic oil filters and tank group (13) are located under the hood directly behind the cab.

Main relief valve (7) is mounted in the inlet side of the control valve next to the lift control valve. Oil flows from the attachment pump section to relief valve (7) before entering the control valves.

The main relief valve keeps supply pressure to the control valve group at 24 150 ± 350 kPa (3500 ± 50 psi) maximum.

Optional ride control group solenoid valve (2) and accumulators (1) are located ahead of the articulation joint on the frame.

Pilot Control Valves And Hydraulic Lockout Valve Location
(12) Pilot control valves group. (16) Hydraulic lockout valve.

Pilot control valves (12) and hydraulic lockout valve (16) are located on the right side of the machine. Access is gained from under the cab or by removing the console cover.

Hydraulic Lockout And Control Levers Location
(18) Multifunction control lever. (19) Auxiliary control lever. (20) Hydraulic lockout lever.

Optional multifunction control lever (18) and auxiliary control lever (19) are located on the right side of the operator's station next to the seat. Control lever (18) allows bucket lift and bucket tilt to be controlled from one lever.

The standard control lever arrangement consists of one lever for tilt function, and a separate lever for lift function. The standard control lever arrangement also allows use of an auxiliary control lever, and it is in the same location as shown in the previous photo of the optional multifunction lever arrangement.

Hydraulic lockout lever (20) controls hydraulic lockout valve (16). When the lockout valve is in the locked position, pilot oil to the pilot control valves is blocked. In this position the bucket cannot be operated.

Pilot Circuits

Oil for the pilot circuits comes from the propulsion system charge pump section. The oil flows from the pump into an accumulator. Then the oil flows through the hydraulic lockout valve and into the pilot control valves.

When the machine is equipped with the standard hydraulic system a separate lift control lever and tilt control lever are the components. The lift control lever activates the pilot valve to cause the bucket to raise or lower. The tilt control lever activates the pilot valve to cause the bucket to dump or tilt back.

When the machine is equipped with an optional auxiliary implement hydraulic system, an additional auxiliary control valve, and an auxiliary attachment is also a part of the attachment system. To control this optional attachment, an auxiliary control lever is added in the operator's station.

The hydraulic control lockout lever is used to block pilot oil flow to the pilot control valves. When the lock is moved toward the operator, oil flow is blocked. This will not permit the levers to actuate the main control valve spools.

The pilot valves are closed center, two spool arrangements. The two spools are held in a center position by springs, when the control levers are in the HOLD position.

Main Control Circuits

Main Control Valve
(1) Outlet to tank. (2) Outlet to auxiliary cylinder. (3) Outlet to auxiliary cylinder. (4) Outlet to tilt cylinder head end. (5) Outlet to tilt cylinder rod end. (6) Outlet to lift cylinders rod end. (7) Outlet to lift cylinders head end. (8) Pump inlet. (9) Main relief valve.

The bucket hydraulic control system is an parallel series system. Although the system is a series system, internal passages and check valves in the lift and tilt control valves allow for some parallel flow. There are separate systems for each of the auxiliary, lift and tilt cylinders on the machine.

Both the auxiliary and tilt control valves have two relief valves, one for each end of the cylinder(s). The two control valves also have load check valves in the cylinder lines. The lift control valve has a check valve in the cylinder rod end line and uses main system pressure relief valve (9) for circuit protection.

When the control levers are placed in the HOLD position the position of the pilot valves block pilot oil flow. No pilot oil can then flow to the control valves and they are held in a center (HOLD) position by springs.

Since the bucket hydraulic system has check valves in the lift and tilt lines, movement of the bucket when the engine is stopped is still possible. Because of the check valves, the weight of the load or bucket allows cylinder oil to flow and lower the bucket, dump the bucket or lower the machine back to the ground.

Kickout Circuits

The pilot valve for the lift system has detents in two positions: RAISE and FLOAT. The lift kickout control will make the lever for the pilot control valve return to the HOLD position when the bucket reaches the desired height.

The distance that the bucket will raise can be controlled by an adjustment in the position of the lift kickout switch.

The pilot valve for bucket tilt has one detent in the TILT BACK circuit. The tilt back kickout control will cause the lever on the tilt pilot control valve to return to the HOLD position when the desired bucket angle is reached. An adjustment can be made to change the desired bucket angle.

Introduction - IT14G

Hydraulic System Schematic
(1) Ride control accumulators. (2) Ride control solenoid valve. (3) Lift cylinders. (4) Tilt cylinders. (5) Coupler cylinder. (6) Lines to auxiliary cylinders. (7) Dead engine lower valve. (8) Main relief valve. (9) Rotary shutoff valve. (10) Main control valves group. (11) Line to steering system. (12) Hydraulic pump group. (13) Pilot oil accumulator. (14) Attachment pilot control valves group. (15) Hydraulic oil filters and tank group. (16) Pilot supply line from propulsion charge pump. (17) Hydraulic oil cooler. (18) Hydraulic lockout valve. (19) Return line from propulsion system.

The main components of the hydraulic system are hydraulic oil filters and tank group (15), pump group (12), main relief valve (8), main control valves group (10), hydraulic oil cooler (17), pilot oil accumulator (13), attachment pilot control valves group (14), coupler cylinder (5), tilt cylinders (4), lift cylinders (3), rotary shutoff valve (9) and various check valves and lines.

NOTE: For more information on the steering system pump section of pump group (12), see SENR6769, 914G Wheel Loader and IT14G Integrated Toolcarrier, Steering System Specifications and SENR6770, 914G Wheel Loader and IT14G Integrated Toolcarrier, Steering System System Operation, Testing And Adjusting.

Pump Group And Hydraulic Oil Cooler Location
(12) Pump group. (17) Hydraulic oil cooler.

Pump group (12) and hydraulic oil cooler (17) are located at the rear of the machine. The oil cooler is located next to the radiator. Access to the oil cooler is gained by raising the engine cover.

Pump group (12) is a two section, gear type pump. The pump group is mounted to the engine on the right side of the machine. Access to the pump group is gained by removing a panel on the right side of the machine.

Coupler Cylinder, Rotary Shutoff Valve, Ride Control Components, Tilt Cylinders, Lift Cylinders, Hydraulic Oil Filter And Tank Group Location
(1) Ride control accumulators. (2) Ride control solenoid valve. (3) Lift cylinders. (4) Tilt cylinders. (5) Coupler cylinder. (9) Rotary shutoff valve. (13) Pilot oil accumulator. (15) Hydraulic oil filter and tank group.

Coupler cylinder (5), tilt cylinders (4) and lift cylinders (3) are all located on the front of the machine.

Rotary shutoff valve (9) is located near the coupler cylinders.

Pilot oil accumulator (13) and hydraulic oil filter and tank group (15) are located under the hood directly behind the cab.

Optional ride control group solenoid valve (2) and accumulators (1) are located ahead of the articulation joint on the frame.

Pilot Control Valves, Main Control Valves And Main Relief Valve
(8) Main relief valve. (10) Main control valves group. (14) Pilot control valves group. (18) Hydraulic lockout valve.

Pilot control valves group (14) and hydraulic lockout valve (18) are located on the right side of the machine. Access is gained from under the cab or by removing the console cover.

Main control valves group (10) is located inside the front loader frame. Access is gained by removing a panel on the front of the loader frame.

Main relief valve (8) is mounted in the inlet side of the control valve next to the lift control valve. Oil flows from the attachment pump section to relief valve (8) before entering the control valves.

The main relief valve keeps supply pressure to the control valve group at 24 150 ± 350 kPa (3500 ± 50 psi) maximum.

Hydraulic Lockout And Control Levers Location
(20) Coupler control lever. (21) Auxiliary control lever. (22) Multifunction control lever. (23) Hydraulic lockout lever.

Optional multifunction control lever (22), auxiliary control lever (21) and coupler control lever (20) are located on the right side of the operator's station next to the seat. Control lever (22) allows bucket lift and bucket tilt to be controlled from one lever. Optional auxiliary control lever (21) controls an optional attachment.

The standard control lever arrangement consists of one lever for tilt function, and a separate lever for lift function. When the machine is equipped with the standard control lever arrangement the coupler control lever is in the same location as with the optional multifunction lever arrangement.

Hydraulic lockout lever (23) controls hydraulic lockout valve (18). When the lockout valve is in the locked position, pilot oil to the pilot control valves is blocked. In this position the bucket cannot be operated.

Pilot Circuits

When the machine is equipped with the standard hydraulic system a separate lift control lever and tilt control lever are the components. The lift control lever activates the pilot valve to cause the attachment to raise or lower. The tilt control lever activates the pilot valve to cause the attachment to dump or tilt back. The coupler control lever activates the pilot valve to cause the coupler to engage or disengage.

When the machine is equipped with an optional fourth function implement hydraulic system, it has an additional auxiliary control valve and an auxiliary attachment. To control this optional attachment, an auxiliary control lever is added in the operator's station.

The pilot valves are closed center, two spool arrangements. The two spools are held in a center position by springs, when the control levers are in the HOLD position.

Main Control Circuits

Main Control Valve
(1) Outlet to tank. (2) Outlet to auxiliary cylinder. (3) Outlet to auxiliary cylinder. (4) Outlet to coupler cylinder rod end. (5) Outlet to coupler cylinder head end. (6) Outlet to tilt cylinders head end. (7) Outlet to tilt cylinders rod end. (8) Outlet to lift cylinders head end. (9) Outlet to lift cylinders rod end. (10) Pump inlet. (11) Main relief valve.

The attachment hydraulic control system is an parallel series system. Although the system is a series system, internal passages and check valves in the lift and tilt control valves allow for some parallel flow. There are separate systems for each of the lift, tilt, coupler and optional auxiliary cylinders on the machine.

The tilt, coupler and optional auxiliary control valves have two relief valves, one for each end of the cylinder(s). The tilt control valve also has load check valves in the cylinder lines. The lift control valve has a check valve in the cylinder rod end line and uses main system pressure relief valve (11) for circuit protection.

When the control levers are placed in the HOLD position the position of the pilot valves blocks pilot oil flow. No pilot oil can then flow to the control valves and they are held in a center (HOLD) position by springs.

Since the attachment hydraulic system has check valves in the lift, tilt and optional auxiliary lines movement of the attachment when the engine is stopped is still possible. Because of the check valves, the weight of the load or attachment allows cylinder oil to flow and lower the attachment, dump a bucket or lower the machine back to the ground.

Kickout Circuits

The distance that the attachment will raise can be controlled by an adjustment in the position of the lift kickout switch.

The pilot valve for attachment position has one detent in the TILT BACK circuit. The tilt back kickout control will cause the lever on the tilt pilot control valve to return to the HOLD position when the desired attachment angle is reached. An adjustment can be made to change the desired attachment angle.

Two controllers mounted on the right tilt cylinder and a switch mounted in the operator's station allow for two attachment positions.

The pilot valve for the coupler system has one detent in the ENGAGE circuit. The coupler control will cause the lever on the coupler pilot control valve to return to the HOLD position when the coupler engages.

Hydraulic Pump Group

Two Section Hydraulic Pump Group
(1) Attachment system section. (2) Steering system section.

The hydraulic pump group is made up of two sections. Steering system section (2) is a gear type pump. The steering section provides the oil needed to operate the steering hydraulic system.

NOTE: For more information on the steering system pump section of the pump group, see SENR6769, 914G Wheel Loader and IT14G Integrated Toolcarrier, Steering System Specifications and SENR6770, 914G Wheel Loader and IT14G Integrated Toolcarrier, Steering System System Operation, Testing And Adjusting.

Attachment system section (1) is also a gear type pump. The attachment section provides the oil needed to operate the bucket/attachment and any attachments in the attachment hydraulic system.

Both pump sections rotate on a common shaft. The steering and attachment sections draw oil from the hydraulic tank through separate inlets. Each section has its own outlet.

Pilot Circuits

Tilt Pilot Control Valve

Tilt Pilot Control Valve
(1) Pivot plate. (2) TILT BACK upper plunger. (3) DUMP upper plunger. (4) Kickout coil assembly. (5) Retainer. (6) Retainer. (7) Centering spring. (8) Centering spring. (9) Lower plunger. (10) Lower plunger. (11) Retainer. (12) Retainer. (13) Centering spring. (14) Centering spring. (15) Metering spring. (16) Metering spring. (17) Metering stem. (18) Metering stem. (19) Port to main control valve. (20) Port to hydraulic tank. (21) Port from pilot pump. (22) Port to main control valve.

With the engine running, oil flows from the propulsion system charge pump into the pilot oil accumulator. The charge pump maintains oil pressure at 2700 ± 200 kPa (390 ± 30 psi) with the engine at low idle. The charge pump maintains oil pressure at 3225 ± 100 kPa (470 ± 15 psi) with the engine at high idle.

The oil flows from the accumulator to the hydraulic lockout valve. When the hydraulic lockout lever is in the up position, the oil is blocked at the lockout valve. When the lever is in the down position, the oil flows through the lockout valve and on to the pilot control valves.

If the engine stops running, or the propulsion charge pump fails with the bucket or attachment in the raised position, the pilot oil accumulator or the dead engine lower valve provide pilot oil to the implement system. The accumulator will supply oil for only a limited amount of time (approximately 5 minutes of operation).

The dead engine lower valve will also enable the bucket/attachment to be lowered. Because of the weight of the load, oil from the lift cylinders to the lift control valve is under pressure. This oil also flows through an orifice into the dead engine lower valve. The oil pressure is reduced and flows through the valve to the pilot control valves.

NOTE: The pilot control valves for the 914G and IT14G are all similar and operate in the same manner. The optional auxiliary control valve on the IT14G does not have kickout coils. The lift control valves for both machines have two kickout coils. All others have one. Only the tilt control valve will be discussed here.

When the valve is in the HOLD position, centering springs (7), (8), (13) and (14) keep pivot plate (1) in its centered position, as shown. Pump oil flows from the hydraulic lockout valve through port (21) to metering stems (17) and (18). In this position the metering stems block the flow of oil to the main control valve and causes it to flow through port (20). Then the oil flows back to the hydraulic tank.

When the control lever is moved to the DUMP position, pivot plate (1) causes upper plunger (3) to move down. As plunger (3) moves down, the force on retainer (6) overcomes spring (8) allowing plunger (3) to contact plunger (10).

Plunger (3) causes plunger (10) to also move down. As plunger (10) moves down, it forces retainer (12) to overcome spring (14). As plunger (10) moves down it causes metering spring (16) and metering stem (18) to move down.

When the metering stem moves down, slots in the metering stem allow pilot oil to flow from port (21) out port (22) to the main control valve.

Centering springs (7) and (13) and metering spring (15) force metering stem (17), lower plunger (9) and upper plunger (2) to move up.

When the control lever is moved to the TILT BACK position, pivot plate (1) causes upper plunger (2) to move down. As plunger (2) moves down the force on retainer (5) overcomes spring (7) allowing plunger (2) to contact plunger (9).

Plunger (2) causes plunger (9) to also move down. As plunger (9) moves down, it forces retainer (11) to overcome spring (13). As plunger (9) moves down, it causes metering spring (15) and metering stem (17) to move down.

When the metering stem moves down, slots in the metering stem allow pilot oil to flow from port (21) out port (19) to the main control valve.

Coil assembly (4) is activated by the bucket positioner. The bucket positioner causes pivot plate (1) to move from the TILT BACK position to the HOLD position.

NOTE: See either the subject Bucket Positioner or Attachment/Bucket Positioner for additional information on the operation of the bucket positioner.

Centering springs (8) and (14) and metering spring (16) force metering stem (18), lower plunger (10) and upper plunger (3) to move up.

Tilt Pilot Control Circuit

NOTE: The 914G tilt pilot control circuit will be described here, however the tilt pilot control circuit for the IT14G operates in a similar manner.

The pilot system uses low pressure oil to operate the main control valves. The main components of the pilot system are pump group (10), lockout valve (16) and pilot valves (12).

With the engine running, oil flows from hydraulic tank (13) to the propulsion charge pump. The oil flows from the pump to accumulator (11) and on to hydraulic lockout valve (16). The propulsion charge pump maintains pilot system pressure at 3225 ± 100 kPa (470 ± 15 psi).

NOTE: For more information on the propulsion charge pump, see SENR6765, 914G Wheel Loader and IT14G Integrated Toolcarrier, Power Train Specifications and SENR6766, 914G Wheel Loader and IT14G Integrated Toolcarrier, Power Train System Operation, Testing And Adjusting.

From the hydraulic lockout valve the oil flows into the pilot control valves. The tilt control pilot valve is a closed center valve that has three positions, TILT BACK, HOLD and DUMP. The oil can not flow through the valve when it is in the HOLD position because it is a closed center valve.

Oil lines connect the output of the tilt control pilot valve to the pilot inlets on the tilt main control valve.

When the control lever on the tilt control pilot valve is moved to the DUMP position, oil flows through oil lines to the ends of the tilt main control valve. This causes the main control valve spool to move. Movement of the spool opens passages for implement pressure oil to flow to the rod end of the tilt cylinder.

Spool movement also opens a passage for return oil from the head end of the tilt cylinder to flow back to hydraulic tank (13). Implement pressure oil acts on the rod end of the tilt cylinder and, because the head end of the cylinder is now vented to tank, the bucket will dump.

When the control lever on the tilt control pilot valve is moved to the TILT BACK position, oil flows through oil lines to the ends of the tilt main control valve. This causes the main control valve spool to move in the opposite direction.

Movement of the spool in this direction opens passages for pressure oil to flow to the head end of the tilt cylinder. Spool movement also opens a passage for return oil from the rod end of the tilt cylinder to flow back to the hydraulic tank. Implement pressure oil acts on the head end of the tilt cylinder and because the rod end of the cylinder is now vented to tank, the bucket will tilt back.

The other pilot control circuits work in the same manner.

Main Circuits - 914G

The control valves for the auxiliary, lift and tilt operations of the bucket are all part of main control valves (8). They are all pilot operated and each valve controls the flow of oil from the attachment section of pump group (10). The pilot control valves are activated by a control lever in the operator's station.

The tilt control lever is attached to the tilt pilot control valve. When the lever is moved it causes the tilt main control valve to route oil from the attachment pump section of pump group (10) to the rod ends or the head ends of tilt cylinder (4).

The lift control lever is attached to the lift pilot control valve. When the lever is moved it causes the lift main control valve to route oil from the attachment pump section of pump group (10) to the head ends or the rod ends of lift cylinders (3).

The auxiliary control lever is attached to the auxiliary pilot control valve. When the lever is moved it causes the auxiliary main control valve to route oil from the attachment pump section of pump group (10) to the rod ends or the head ends of the auxiliary cylinders through lines (5).

Relief valves mounted in the auxiliary and tilt main control valves maintain their respective attachment system pressure. The relief valves also reduce the possibility of damage to the circuit components when the control valves are actuated. Relief valves in the auxiliary and tilt circuit control valves (both head end and rod end) maintain the circuit pressure when the auxiliary and tilt control valves are in the HOLD position.

Main Relief Valve

Main Relief Valve
(1) Inlet passage. (2) Valve. (3) Passage to tank. (4) Spring. (5) Cap. (6) Locknut. (7) Adjusting screw.

The main relief valve is located in the inlet section of the main control valve. The pressure setting for the main relief valve is 24 150 ± 350 kPa (3500 ± 50 psi).

The relief valve is a direct acting type valve. Pressure oil flows into passage (1). The oil acts against the left side of valve (2) which is held closed by the force of spring (4).

When an outside force causes pressure in any of the cylinders to rise, that increase in pressure is also felt in passage (1). As the pressure rises above the valve setting, the oil overcomes the force of spring (4) and causes valve (2) to move to the right.

The oil in passage (1) flows past the open valve and through passages (3) back to the hydraulic tank.

The pressure in the cylinders can not increase any more. When oil pressure returns to below relief valve setting, spring (4) moves valve (2) back to the left onto its seat.

The relief valve pressure setting is adjusted by removing cap (5), loosening locknut (6) and turning adjusting screw (7). Turning adjusting screw (7) clockwise to increase pressure setting and counterclockwise to decrease pressure setting.

Main Circuits - IT14G

The optional auxiliary control valve, coupler control valve, tilt control valve and lift control valve are all part of main control valves (10). They are all pilot operated and each valve controls the flow of oil from the attachment section of pump group (12). The pilot control valves are activated by control levers in the operator's station.

The tilt control lever is attached to the tilt pilot control valve. When the lever is moved it allows pilot oil to flow to the tilt main control valve. This causes the tilt main control valve to route oil from the attachment pump section of pump group (12) to the rod ends or the head ends of tilt cylinders (4).

The tilt control lever is attached to the lift pilot control valve. When the lever is moved it allows pilot oil to flow to the lift main control valve. This causes the lift main control valve to route oil from the attachment pump section of pump group (12) to the rod ends or the head ends of lift cylinders (3).

The coupler control lever is attached to the coupler pilot control valve. When the lever is moved it allows pilot oil to flow to the coupler main control valve. This causes the coupler main control valve to route oil from the attachment pump section of pump group (12) to the rod ends or the head ends of coupler cylinder (5).

The auxiliary control lever is attached to the auxiliary pilot control valve. When the lever is moved it causes the auxiliary main control valve to route oil from the attachment pump section of pump group (12) to the rod ends or the head ends of the auxiliary cylinders through lines (6).

Main relief valve (8) maintains attachment system pressure and reduces the possibility of damage to the circuit components when the control valves are actuated. The auxiliary, coupler and tilt circuits control valves have relief valves (both head end and rod end) that maintain the circuit pressure when their control valve is in the HOLD position. Both of the tilt relief valves have a makeup valve feature that helps prevent cavitation during cylinder movement.

The lift circuit has no line relief valves and is protected by main relief valve (8). A makeup valve in the lift rod end circuit helps prevent cavitation during LOWER operations.

Main Relief Valve

Main Relief Valve
(1) Inlet passage. (2) Valve. (3) Passage to tank. (4) Spring. (5) Cap. (6) Locknut. (7) Adjusting screw.

The main relief valve is located in the inlet section of the main control valve. The pressure setting for the main relief valve is 24 150 ± 350 kPa (3500 ± 50 psi).

The relief valve is a direct acting type valve. Pressure oil flows into passage (1). The oil acts against the left side of valve (2) which is held closed by the force of spring (4).

The oil in passage (1) flows past the open valve and through passages (3) back to the hydraulic tank.

The pressure in the cylinders can not increase any more. When oil pressure returns to below relief valve setting, spring (4) moves valve (2) back to the left onto its seat.

Lift Control Valve

Lift Control Valve - HOLD Position
(1) Port to rod end of lift cylinders. (2) Port to head end of lift cylinders. (3) Lift cylinder rod end makeup valve. (4) Passage. (5) Check valve. (6) Inlet from pump. (7) Pilot oil port. (8) Pilot oil port. (9) Spring. (10) Valve spool. (11) Passage to next control valve. (12) Passage to tank. (13) Passage from pump. (14) Passage to next control valve. (15) Spring.

Lift Control Valve HOLD Position

NOTE: The lift control valve is the same for both machines.

The lift control valve is the first control valve in the valve group series. When the control valve is in the HOLD position, the oil flows into port (6) and passage (13), around spool (10) into passages (11) and (14).

The oil flows through passages (11) and (14) into the tilt control valve. If the tilt valve is also in the HOLD position the oil flows through the tilt valve and into the coupler valve (on the IT) or the auxiliary valve (if equipped). If all the valves are in the HOLD position the oil returns to the hydraulic tank. Passage (12) is a common passage through the valve sections to the tank.

In the HOLD position no pilot oil flows into ports (7) and (8). With no pilot oil acting on either end of spool (10), springs (9) and (15) keep the spool centered. This blocks the flow of oil in ports (1) and (2).

With the oil in the circuits to the lift cylinders blocked, the cylinders can not move until the pilot control lever is moved to either the RAISE, LOWER or FLOAT position.

Lift Control Valve RAISE Position

When the pilot control lever is placed into the RAISE position pilot oil flows into port (8). Pilot oil acts against valve spool (10) and overcomes the force of spring (9) and causes the spool to move left. Pump oil flow from passage (13) into passages (11) and (14) is blocked.

The oil in port (6) increases in pressure until it opens check valve (5). When the check valve opens, the pump oil in port (6) flows past the open check valve into passage (4). Then the oil flows past spool (10) into port (2) and on to the head ends of the lift cylinders.

The pump oil flowing into the head ends of the lift cylinders acts against the pistons and forces the rods to extend causing the bucket/attachment to raise. The oil from the rod ends of the cylinders flows through port (1) past spool (10) and then through passage (12) to the tank.

When the control lever is placed in the HOLD position, pilot oil flow to port (8) stops. With no pilot oil flowing into port (8) spring (9) causes valve spool (10) to return to its HOLD position.

The main relief valve located in the control valve group inlet serves as the lift circuit head end relief valve.

Lift Control Valve LOWER Position

When the pilot control lever is placed into the LOWER position pilot oil flows into port (7). Pilot oil acts against valve spool (10), overcomes the force of spring (9) and causes the spool to move right. Pump oil flow from passage (13) into passages (11) and (14) is blocked.

The pump oil flowing into the rod ends of the lift cylinders acts against the pistons and forces the rods to retract causing the bucket/attachment to lower. The oil from the head ends of the cylinders flows through port (2) past spool (10) and then through passage (12) to the tank.

When the control lever is placed in the HOLD position, pilot oil flow to port (7) stops. With no pilot oil flowing into port (7) spring (9) causes valve spool (10) to return to its HOLD position.

The main relief valve located in the control valve group inlet serves as the lift circuit head end relief valve.

Lift Valve FLOAT Position

When the pilot control lever is placed into the FLOAT position pilot oil flows into port (7). Pilot oil acts against valve spool (10) and overcomes the force of spring (9) and causes the spool to move right. The spool moves right far enough to allow pump oil to flow from passage (13) into passages (11) and (14).

When the control lever is placed into the FLOAT position, an electromagnetic detent holds the pilot valve spool in the FLOAT position. The pilot control valve will remain in detent until the control lever moves the pilot control valve spool out of the detent.

When main valve spool (10) is in FLOAT position, the pump oil flows through passage (13) into passages (11) and (14). The oil flows through passages (11) and (14) to the tilt control valve. The position of valve spool (10) allows the oil in passage (12) to flow to both passages (1) and (2).

With the oil in both ends of the lift cylinders at the same pressure and passages (1) and (2) open to the tank through passage (12), the position of the lift arms is not controlled by the pump oil. With the control lever and valve spool (10) in the FLOAT position, the weight of the lift arms and bucket/attachment will cause the bucket to lower to the ground. As the machine is moved the bucket/attachment will follow the shape of the ground.

Makeup Valve

A makeup valve is located in passage (1) to the rod ends of the lift cylinders. The makeup valve functions when the control valve spool is in either the FLOAT or LOWER position.

A spring combines with oil pressure in the spring chamber to hold makeup valve (3) closed. The makeup valve opens only when the rod ends of the lift cylinders require more pump oil flow than the pump can supply oil to the cylinders. This prevents cavitation in the lift cylinders.

When the flow of oil to the rod ends of the cylinders is not enough, the pressure of the oil in passage (1) is low. The higher return oil pressure in the passage to the tank opens the valve and allows more oil to flow to the rod ends of the cylinders.

Tilt Control Valve - 914G

Tilt Control Valve - HOLD Position
(1) Port to head end of tilt cylinder. (2) Port to rod end of tilt cylinder. (3) Rod end relief valve. (4) Passage. (5) Check valve. (6) Inlet from pump. (7) Head end relief valve. (8) Pilot oil port. (9) Pilot oil port. (10) Spring. (11) Valve spool. (12) Passage to next control valve. (13) Passage to tank. (14) Passage from pump. (15) Passage to next control valve. (16) Spring.

Tilt Control Valve HOLD Position

The tilt control valve is the next control valve in the valve group series. With the engine running, oil flows from the pump and enters the pump inlet. Then the oil flows through the lift control valve into inlet (6) and passage (14).

If the tilt control lever is in the HOLD position the oil flows around valve spool (11), into passages (12) and (15) and on to the auxiliary valve. If the auxiliary valve is also in the HOLD position the oil flows through the auxiliary valve and returns to the hydraulic tank.

In the HOLD position tilt valve spool (11) blocks the flow of oil in ports (1) and (2). With the oil in the circuits to the tilt cylinder stopped, the cylinder can not move until the control lever is moved to either the TILT BACK or DUMP position.

Spring (10) on the left end of valve spool (11) and spring (16) on the right side of the spool keep the spool in the centered position when no pilot oil is routed to the spool.

Tilt Control Valve TILT BACK Position

When the control lever is moved to the TILT BACK position, pilot oil flows from the pilot control valve and enters port (8). Pilot oil overcomes the force of spring (16) on the right side of valve spool (11) and causes the spool to move to the right.

When valve spool (11) moves to the right into the TILT BACK position, pump oil flow from passage (14) into passages (12) and (15) is blocked. The increase in oil pressure in passage (6) opens check valve (5). When the check valve opens, the pump oil in passage (6) flows through the open check valve into passage (4) and out port (1). Then the oil flows to the head end of the tilt cylinder.

The pump oil flowing into the head end of the tilt cylinder forces the rod to extend. The rod extends, causing the bucket to tilt back. Return oil from the rod end of the cylinder flows through port (2) and then through passage (13) to the filter and tank.

Some of the oil in passage (14) does flow to the auxiliary control valve allowing some auxiliary movement. As the need for oil in the tilt cylinder lessens, more oil is available to the auxiliary control valve.

Tilt Control Valve DUMP Position

When the control lever is moved to the DUMP position, pilot oil flows from the pilot control valve and enters port (9). Pilot oil overcomes the force of spring (10) on the left side of valve spool (11) and causes the spool to move to the left.

When valve spool (11) moves to the left into the DUMP position, pump oil flow from passage (14) into passages (12) and (15) is blocked. The increase in oil pressure in passage (6) opens check valve (5). When the check valve opens, the pump oil in passage (6) flows through the open check valve into passage (4) and out port (2). Then the oil flows to the rod end of the tilt cylinder.

The pump oil flowing into the rod end of the tilt cylinder forces the rod to retract. The rod retracts, causing the bucket to dump. Return oil from the head end of the cylinder flows through port (1) and then through passage (13) to the filter and tank.

Some of the oil passage (14) does flow to the auxiliary control valve allowing some auxiliary movement. As the need for oil in the tilt cylinder lessens, more oil is available to the auxiliary control valve.

After the bucket is dumped and the control lever placed in the TILT BACK position, an electromagnet detent assembly in the pilot control valve will hold the control lever in the TILT BACK position until the bucket returns to the desired operating angle.

Makeup And Relief Valves

The two tilt circuit line relief valves are mounted in the tilt control valve. The setting for the rod and head end circuits is 25 500 ± 350 kPa (3700 ± 50 psi).

The relief valves also provide makeup oil to the return side in order to prevent cavitation. Oil in the return loop acts against the valve and causes it to move off its seat. Now the oil flows from the tank passage into the return port and back to the cylinder.

Both the rod and head circuits relief valves are identical and operate the same manner.

Tilt Control Valve - IT14G

Tilt Control Valve - HOLD Position
(1) Port to head end of tilt cylinders. (2) Port to rod end of tilt cylinders. (3) Rod end relief valve. (4) Passage. (5) Check valve. (6) Inlet from pump. (7) Head end relief valve. (8) Pilot oil port. (9) Pilot oil port. (10) Spring. (11) Valve spool. (12) Passage to next control valve. (13) Passage to tank. (14) Passage from pump. (15) Passage to next control valve. (16) Spring.

Tilt Control Valve HOLD Position

If the tilt control lever is in the HOLD position the oil flows around valve spool (11), into passages (12) and (15) and on to the coupler valve. If the coupler valve is also in the HOLD position the oil flows through the coupler valve and returns to the hydraulic tank.

In the HOLD position tilt valve spool (11) blocks the flow of oil in ports (1) and (2). With the oil in the circuits to the tilt cylinders stopped, the cylinders can not until the control lever is moved to either the TILT BACK or DUMP position.

Spring (10) on the left end of valve spool (11) and spring (16) on the right side of the spool keep the spool in the centered position when no pilot oil is routed to the spool.

Tilt Control Valve DUMP Position

When the control lever is moved to the DUMP position, pilot oil flows from the pilot control valve and enters port (8). Pilot oil overcomes the force of spring (16) on the right side of valve spool (11) and causes the spool to move to the right.

When valve spool (11) moves to the right into the DUMP position, pump oil flow from passage (14) into passages (12) and (15) is blocked. The increase in oil pressure in passage (6) opens check valve (5). When the check valve opens, the pump oil in passage (6) flows through the open check valve into passage (4) and out port (1). Then the oil flows to the head end of the tilt cylinders.

The pump oil flowing into the head end of the tilt cylinders forces the rod to extend. The rod extends, causing the bucket to dump. Return oil from the rod end of the cylinders flows through port (2) and then through passage (13) to the filter and tank.

Valve spool (11) allows return oil in port (2) to flow past the spool into passage (4). This oil mixes with pump supply oil in passage (4) in order to reduce cavitation.

Some of the oil in passage (14) does flow to the coupler control valve allowing some coupler movement. As the need for oil in the tilt cylinders lessens, more oil is available to the coupler control valve.

Tilt Control Valve TILT BACK Position

When the control lever is moved to the TILT BACK position, pilot oil flows from the pilot control valve and enters port (9). Pilot oil overcomes the force of spring (10) on the left side of valve spool (11) and causes the spool to move to the left.

When valve spool (11) moves to the left into the TILT BACK position, pump oil flow from passage (14) into passages (12) and (15) is blocked. The increase in oil pressure in passage (6) opens check valve (5). When the check valve opens, the pump oil in passage (6) flows through the open check valve into passage (4) and out port (2). Then the oil flows to the rod end of the tilt cylinders.

The pump oil flowing into the rod end of the tilt cylinders forces the rod to retract. The rod retracts, causing the bucket to TILT BACK. Return oil from the head end of the cylinders flows through port (1) and then through passage (13) to the filter and tank.

Makeup And Relief Valves

The two tilt circuit line relief valves are mounted in the tilt control valve. The setting for the rod end circuit is 25 500 ± 350 kPa (3700 ± 50 psi). The setting for the head end circuit is 13 100 ± 350 kPa (1900 ± 50 psi).

Both the rod and head circuits relief valves are identical and operate the same manner.

Auxiliary Control Valve (Optional) - 914G

Auxiliary Control Valve - HOLD Position
(1) Port to head end of auxiliary cylinders. (2) Port to rod end of auxiliary cylinders. (3) Rod end relief valve. (4) Passage. (5) Check valve. (6) Inlet from pump. (7) Head end relief valve. (8) Pilot oil port. (9) Pilot oil port. (10) Spring. (11) Valve spool. (12) Passage to outlet manifold. (13) Passage to tank. (14) Passage from pump. (15) Passage to outlet manifold. (16) Spring.

Auxiliary Control Valve HOLD Position

The optional auxiliary control valve (if equipped) is the last control valve in the valve group series. With the engine running, oil flows from the pump and enters the pump inlet. Then the oil flows through the tilt control valve into inlet (6) and passage (14).

If the auxiliary control lever is in the HOLD position the oil flows around valve spool (11), into passages (12) and (15) and returns to the hydraulic tank.

In the HOLD position auxiliary valve spool (11) blocks the flow of oil in ports (1) and (2). With the oil in the circuits to the auxiliary cylinders stopped, the cylinders can not move until the control lever is moved to either the CLOSE or OPEN position.

Spring (10) on the left end of valve spool (11) and Spring (16) on the right side of the spool keep the spool in the centered position when no pilot oil is routed to the spool.

Auxiliary Control Valve CLOSE Position

When the control lever is moved to the CLOSE position, pilot oil flows from the pilot control valve and enters port (8). Pilot oil overcomes the force of spring (16) on the right side of valve spool (11) and causes the spool to move to the right.

When valve spool (11) moves to the right into the CLOSE position, pump oil flow from passage (14) into passages (12) and (15) is blocked. The increase in oil pressure in passage (6) opens check valve (5). When the check valve opens, the pump oil in passage (6) flows through the open check valve into passage (4) and out port (1). Then the oil flows to the head end of the auxiliary cylinders.

The pump oil flowing into the head end of the auxiliary cylinders forces the rod to extend. The rod extends, causing the attachment to close. Return oil from the rod end of the cylinders flows through port (2) and then through passage (13) to the filter and tank.

Auxiliary Control Valve OPEN Position

When the control lever is moved to the OPEN position, pilot oil flows from the pilot control valve and enters port (9). Pilot oil overcomes the force of spring (10) on the left side of valve spool (11) and causes the spool to move to the left.

When valve spool (11) moves to the left into the OPEN position, pump oil flow from passage (14) into passages (12) and (15) is blocked. The increase in oil pressure in passage (6) opens check valve (5). When the check valve opens, the pump oil in passage (6) flows through the open check valve into passage (4) and out port (2). Then the oil flows to the rod end of the auxiliary cylinders.

The pump oil flowing into the rod end of the auxiliary cylinders forces the rod to retract. The rod retracts, causing the attachment to open. Return oil from the head end of the cylinders flows through port (1) and then through passage (13) to the filter and tank.

After the attachment is opened and the control lever placed in the CLOSE position, an electromagnet detent assembly in the pilot control valve will hold the control lever in the CLOSE position until the control lever returns to HOLD or OPEN position.

Relief Valves

The two auxiliary circuit line relief valves are mounted in the auxiliary control valve. The setting for the rod and head end circuits is 25 500 ± 350 kPa (3700 ± 50 psi).

Both the rod and head circuits relief valves are identical and operate in the same manner.

Coupler Control Valve - IT14G

Coupler Control Valve - HOLD Position
(1) Port to rod end of coupler cylinder. (2) Port to head end of coupler cylinder. (3) Rod end relief valve. (4) Passage. (5) Check valve. (6) Inlet from pump. (7) Head end relief valve. (8) Pilot oil port. (9) Pilot oil port. (10) Spring. (11) Valve spool. (12) Passage to next control valve. (13) Passage to tank. (14) Passage from pump. (15) Passage to next control valve. (16) Spring.

Coupler Control Valve HOLD Position

The coupler control valve is the last control valve in the valve group series (unless the machine is equipped with an optional auxiliary control valve). With the engine running, oil flows from the pump and enters the pump inlet. Then the oil flows through the tilt control valve into inlet (6) and passage (14).

If the coupler control lever is in the HOLD position the oil flows around valve spool (11), into passages (12) and (15) and on to the auxiliary valve (if equipped) or the hydraulic tank. If equipped with an auxiliary valve and it is also in the HOLD position the oil flows through the auxiliary valve and returns to the hydraulic tank.

In the HOLD position coupler valve spool (11) blocks the flow of oil in ports (1) and (2). With the oil in the circuits to the coupler cylinder stopped, the cylinder can not move until the control lever is moved to either the ENGAGE or DISENGAGE position.

Spring (10) on the left end of valve spool (11) and spring (16) on the right side of the spool keep the spool in the centered position when no pilot oil is routed to the spool.

Coupler Control Valve DISENGAGE Position

When the control lever is moved to the DISENGAGE position, pilot oil flows from the pilot control valve and enters port (8). Pilot oil overcomes the force of spring (16) on the right side of valve spool (11) and causes the spool to move to the right.

When valve spool (11) moves to the right into the DISENGAGE position, pump oil flow from passage (14) into passages (12) and (15) is blocked. The increase in oil pressure in passage (6) opens check valve (5). When the check valve opens, the pump oil in passage (6) flows through the open check valve into passage (4) and out port (1). Then the oil flows to the rod end of the coupler cylinder.

The pump oil flowing into the rod end of the coupler cylinder forces the rod to retract. The rod retracts, causing the attachment to DISENGAGE. Return oil from the head end of the cylinder flows through port (2) and then through passage (13) to the filter and tank.

Some of the oil in passage (14) does flow to the auxiliary control valve (if equipped) allowing some auxiliary movement. As the need for oil in the coupler cylinder lessens, more oil is available to the auxiliary control valve.

Coupler Control Valve ENGAGE Position

When the control lever is moved to the ENGAGE position, pilot oil flows from the pilot control valve and enters port (9). Pilot oil overcomes the force of spring (10) on the left side of valve spool (11) and causes the spool to move to the left.

When valve spool (11) moves to the left into the ENGAGE position, pump oil flow from passage (14) into passages (12) and (15) is blocked. The increase in oil pressure in passage (6) opens check valve (5). When the check valve opens, the pump oil in passage (6) flows through the open check valve into passage (4) and out port (2). Then the oil flows to the head end of the coupler cylinder.

The pump oil flowing into the head end of the coupler cylinder forces the rod to extend. The rod extends, causing the attachment to ENGAGE. Return oil from the rod end of the cylinder flows through port (1) and then through passage (13) to the filter and tank.

After the attachment is engaged, an electromagnet detent assembly in the pilot control valve will hold the control lever in the ENGAGED position until the lever returns to either the HOLD or DISENGAGED position.

Relief Valves

The two coupler circuit line relief valves are mounted in the coupler control valve. The setting for the rod and head end circuits is 20 700 ± 350 kPa (3000 ± 50 psi).

Both the rod and head circuits relief valves are identical and operate in the same manner.

Auxiliary Control Valve (Optional) - IT14G

Auxiliary Control Valve HOLD Position

The optional auxiliary control valve (if equipped) is the last control valve in the valve group series. With the engine running, oil flows from the pump and enters the pump inlet. Then the oil flows through the coupler control valve into inlet (6) and passage (14).

If the auxiliary control lever is in the HOLD position the oil flows around valve spool (11), into passages (12) and (15) and returns to the hydraulic tank.

Spring (10) on the left end of valve spool (11) and spring (16) on the right side of the spool keep the spool in the centered position when no pilot oil is routed to the spool.

Auxiliary Control Valve CLOSE Position

Auxiliary Control Valve OPEN Position

Relief Valves

The two auxiliary circuit line relief valves are mounted in the auxiliary control valve. The setting for the rod and head end circuits is 20 700 ± 350 kPa (3000 ± 50 psi).

Both the rod and head circuits relief valves are identical and operate in the same manner.

Kickout Systems

Lift Kickout

Lift Kickout Components - 914G
(1) Solid state switch (normally closed). (2) Switch holder assembly. (3) Magnet assembly.

Lift Kickout Components - IT14G
(1) Solid state switch (normally closed). (2) Switch holder assembly. (3) Magnet assembly.

The lift kickout group consists of solid state switch (1) (located on right side of the 914G loader frame and the right side of the IT14G frame), magnet assembly (3) (located on lift arm pivot) and an electromagnet detent (part of the lift pilot control valve). Solid state switch (1) is normally closed and only opens when magnet assembly (3) makes contact.

When the operator moves the lift control lever to the RAISE position, the bottom of pilot control valve spool contacts an energized electromagnet. The electromagnet will hold the lift control lever in the RAISE position.

As the bucket lifts, magnet assembly (3) on the lift arm pivot moves in the direction of normally closed solid state switch (1) on the loader frame. When the magnet assembly gets near the switch, it opens the switch. This stops the flow of current to the electromagnet and breaks the electric circuit.

With no current flow, the electromagnet detent no longer is able to hold the valve spool. A spring moves the pilot valve spool and the control lever up to the HOLD position.

The lift arms stop just before the lift cylinder rods are fully extended. The lift arms will stay at this position until the operator places the lift control lever in the LOWER position.

When the operator moves the lift control lever to the LOWER position the lift arms will lower. As magnet assembly (3) moves away from solid state switch (2), the switch will return to its normally closed position.

NOTE: For more information on the lift kickout, see SEBU6868, 914G Wheel Loader, Operation & Maintenance Manual, or SEBU6869, IT14G Integrated Toolcarrier, Operation & Maintenance Manual.

Bucket Positioner Group - 914G

Bucket Positioner Components
(1) Tube. (2) Electronic control group. (3) Magnet

The bucket positioner group consists of tube (1) (mounted on the tilt cylinder), electronic control group (2) (mounted on the tube), magnet (3) (mounted on linkage) and an electromagnet detent (part of tilt pilot control valve).

When the operator places the tilt control lever to the TILT BACK position, the bottom of the pilot control valve spool contacts an energized electromagnet. The electromagnet will hold the lift control lever in the TILT BACK position.

As the bucket tilts back, the tilt cylinder rod moves out towards control group (2) mounted on tube (1). When magnet (3) gets near the switch, it opens the switch. This stops the flow of current to the electromagnet and breaks the electric circuit.

With no current flow, the control valve electromagnet detent no longer is able to hold the control valve spool. A spring moves the valve spool and the control lever to the HOLD position.

The bucket stops at the correct angle to operate. The bucket will stay in this position until the operator places the control lever in the DUMP position.

NOTE: For more information on the bucket positioner switch, see SEBU6868, 914G Wheel Loader, Operation & Maintenance Manual.

Bucket/Attachment Positioner Group - IT14G

Attachment Positioner Components
(1) Solid state switch (for attachment positioner operation). (2) Positioner switch holder assembly. (3) Solid state switch (for bucket positioner operation). (4) Magnet assembly.

Tilt Control Valve Components
(5) Electromagnet. (6) Plate. (7) Spring. (8) Tilt pilot control valve spool.

Control Panel
(9) Control switch.

The bucket positioner group consists of positioner switch holder assembly (2) (located on the right side tilt cylinder), solid state switches (1) and (3) (mounted in switch holder assembly), magnet assembly (4) (located on the left side tilt cylinder rod end), electromagnet (5) (part of tilt pilot control valve) and control switch (9) (located in the operator compartment).

Solid state switch (1) is for attachment operation and switch (3) is for bucket/attachment operation. Control switch (9), located in a panel in the operator compartment, will allow the use of either the bucket or attachment positioner switch for operation. This will permit the operator to change attachments without readjusting the position of the switches in the control group.

When the operator places control switch (9) in the bucket position and moves the tilt control lever to the TILT BACK position, plate (6) contacts energized electromagnet (5). The electromagnet will hold the lift pilot control lever in TILT BACK position.

As the bucket tilts back, magnet assembly (4) on the right side tilt cylinder rod end moves in the direction of normally closed solid state switch (3). When the magnet assembly gets near the switch, it opens the switch. This stops the flow of current flow to the electromagnet and breaks the electric circuit.

With no current flow, electromagnet (5) no longer is able to hold plate (6). Spring (7) moves pilot control valve spool (8) and the pilot control lever back to the HOLD position.

The bucket stops at the correct angle to operate. The bucket will stay in this position until the operator places the control lever in the DUMP position.

When the operator places control switch (9) in the attachment position and moves the tilt control lever to the TILT BACK position, plate (6) contacts energized electromagnet (5). The electromagnet will hold the lift pilot control lever in TILT BACK position.

As the attachment tilts back, magnet assembly (4) on the right side tilt cylinder rod end moves in the direction of normally closed solid state switch (1). When the magnet assembly gets near the switch, it opens the switch. This stops the flow of current flow to the electromagnet and breaks the electric circuit.

With no current flow, electromagnet (5) no longer is able to hold plate (6). Spring (7) moves pilot control valve spool (8) and the pilot control lever back to the HOLD position.

The attachment stops at the correct angle to operate. The attachment will stay in this position until the operator places the control lever in the DUMP position.

NOTE: For more information on the bucket/attachment positioner and switch, see SEBU6869, IT14G Integrated Toolcarrier, Operation & Maintenance Manual.

Ride Control Circuit

Ride Control Schematic
(1) Ride control accumulators. (2) Ride control solenoid valve. (3) Lift cylinders. (4) Return line. (5) Lift control valve. (6) Hydraulic oil filters and tank group. (7) Attachment pump section.

The optional ride control system provides a means for absorbing and dampening the bucket forces which produce the pitching motion as the machine travels on rough terrain. The main components of the ride control system are lift cylinders (3), solenoid valve (2) and accumulators (1).

Ride Control Component Location
(1) Accumulator. (2) Solenoid valve. (3) Lift cylinder.

Solenoid valve (2), accumulators (1) and lift cylinders (3) are located on the front frame of the loader just ahead of the articulation joint.

Control Switch Location
(8) Control switch.

Control switch (8) is mounted in the control panel in the operator's station. The control switch is a three position switch, OFF, ON and AUTO.

Solenoid valve (2) is a normally closed valve. When the lift control valve is in the HOLD position and the switch in the operator panel is in the OFF position, coils inside the valves are not energized. A spring in each valve holds the spool inside the valve in the up position. In this position oil that flows from the head ends of lift cylinders (3) can also flow through an orifice at solenoid valve (2) to accumulators (1).

Rod end oil is blocked at solenoid valve (2) and flows back to hydraulic tank (6) through lift control valve (5).

When the lift control valve is in the HOLD position and the switch in the operator panel is pushed to the ON position, the coils in each solenoid valve are energized. When the coil is energized it causes the spool inside the valve to overcome spring tension and move down. When the spool moves down it opens a path for head end and rod end oil to flow through the solenoid valve (2).

As the machine moves across a rough terrain with a loaded bucket, the forces of the load act against the lift cylinders. When the load acts against the head end of the cylinders, that oil tries to flow through solenoid valve (2) into the accumulators.

The accumulators have a nitrogen precharged bladder that resists the oil flow and acts as a shock absorber. Rod end make up oil can flow through solenoid valve (2) and line (4).

An additional pressure switch is installed in the tilt circuit on the IT machines. When the operator places the tilt control lever in the TILT BACK position the ride control system is switched off. This prevents the IT tilt cylinders from causing the lift arms to raise when the tilt links bottom out against them.

When the lift control valve is in the HOLD position and the switch in the operator panel is pushed to the AUTO position, the coils in each solenoid valve are energized and function the same as in ON position. As the operator approaches the load area, the machine is slowed. When machine speed is reduced enough the ride control system is switched off allowing for greater breakout force.

After the operator fills the bucket and moves the machine to the dump site machine speed increases. As speed increases the ride control system is switched back on. Travel over rough terrain is dampened by the ride control system as described before.

NOTE: For more information on the ride control switch, see SEBU6868, 914G Wheel Loader, Operation & Maintenance Manual, or SEBU6869, IT14G Integrated Toolcarrier, Operation & Maintenance Manual.