The pilot hydraulic control system controls the movement of the implements through the flow of pilot oil to the end caps of the main control valve. The pilot hydraulic control system is made up of the following components: the pilot/brake pump, the pilot valve (oil manifold), ball valve (hydraulic lockout), the pilot control valve, the control levers, the detent coils and the ball switch (hydraulic lockout detent override).
Note: Illustration 1 shows a machine without an auxiliary function (logging fork, side dump bucket, multipurpose bucket, etc). The operation of the auxiliary function is similar to the lift function and the tilt function. The auxiliary function is not equipped with detent coils.
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| Illustration 1 | g00294500 |
Right Side View of the Pilot Hydraulic System (1) Lift control lever. (2) Tilt control lever. (3) Pilot valve. (4) Hydraulic lockout lever (LOCKED). (5) Hydraulic lockout lever (UNLOCKED). (6) Supply line to pilot control valve. (7) Pilot line (RAISE position). (8 ) Pilot line (TILT BACK position). (9) Return line to hydraulic oil tank. (10) Pilot line (LOWER position). (11) Pilot line (DUMP position). | |
The following items are located to the right of the operator's seat: Hydraulic lockout (5), pilot valve (3), tilt control lever (2) and lift control lever (1). Tilt control lever (2) and lift control lever (1) are attached to pilot valve (3) .
Pilot oil is supplied to the pilot valve (oil manifold) by the pilot/brake pump. The oil flows into the pilot valve (oil manifold). This valve reduces the pressure of the pilot oil. Then, the pilot oil flows through the ball valve (hydraulic lockout) and into the supply line (6) to pilot control valve (3). On a standard machine, the pilot valve is equipped with two separate valves. One valve is for the lift function and the other valve is for the tilt function. Also, the pilot valve may be equipped with a third valve for an auxiliary function.
When the operator moves lift control lever (1) to the RAISE position, pilot oil flows through pilot pressure oil line (7) to an end cap in the main control valve. The flow of pilot oil in the end cap places oil pressure against the valve spool. The movement of the valve spool allows pump supply oil from the implement pump to flow to the lift cylinders.
Pilot oil from the opposite end of the valve spool flows through oil line (10) and back to the hydraulic tank through return line (9) .
Note: The flow of oil through pilot pressure oil line (7) and (10) reverses when lift control lever (1) is moved to the LOWER position.
When the operator moves tilt control lever (2) to the TILT BACK position, pilot pressure oil flows through pilot pressure oil line (8) to an end cap in the main control valve. The flow of pilot oil in the end cap places oil pressure against the valve spool. The movement of the valve spool allows pump supply oil from the implement pump to flow to the tilt cylinder.
Pilot oil from the opposite end of the valve spool flows through pilot line (11) and back to the hydraulic tank through return line (9) .
Note: The flow of oil through hydraulic oil lines (8) and (11) reverses when tilt control lever (2) is moved to the DUMP position.
The pilot hydraulic control system is equipped with a ball valve (hydraulic lockout). The ball valve is used in order to disable the implement system. When the ball valve is in the LOCKED position (4), the flow of pilot oil to pilot valve (3) is blocked. The control levers can still move, but the flow of pilot oil to the pilot control valve is blocked.
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| Illustration 2 | g00990112 |
Upper Section of the Pilot Valve (12) Detent coil. | |
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| Illustration 3 | g00991372 |
Hydraulic Lockout (5) Hydraulic lockout lever (UNLOCKED). (13) Ball Switch (hydraulic lockout detent override). (14) Ball valve (hydraulic lockout). | |
The pilot valve is equipped with detent coils. The detent coils are electromagnets that hold the control levers (1, 2) in the full forward position, or full back positions. The levers are held in position until the detent coils are de-energized or the control levers are manually released. When the key start switch is in the ON position, and the hydraulic lockout lever (5) is in contact with the ball switch (hydraulic lockout detent override) (13), current is enabled to flow to the detent coils. Each detent coil (12) has a connector with two contacts. The detent coil for the lift function receives current through wire 761-GY. The detent coil for the tilt function receives current through wire 961-BR. The detent coil for the float receives current through wire F766-White. The other contact is frame ground. Frame ground is wire 200-BK.
When the hydraulic lockout lever (5) is in LOCKED position (4), the control levers will not be held in the DETENT position. The ball switch (hydraulic lockout detent override) that is not in contact with the hydraulic lockout will open. The path of electrical current to the detent coils is interrupted. The lack of electrical current will prevent the control levers from being held in the DETENT position.
Reference: For more information on the operation of the pilot valve, refer to the Service Manual module for Systems Operation, "Pilot Valve, Pilot Valve (Joystick)".
Reference: For more information on the operation of the pilot valve (oil manifold), refer to the Service Manual module for Systems Operation, "Pilot Valve (Oil Manifold)".