TK711, TK721, TK722 and TK732 Track Feller Bunchers Hydraulic System Piston Pump Margin Pressure - Test Caterpillar


Piston Pump Margin Pressure - Test
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1.1. Travel Pump
2.1. Implement Pump

------ WARNING! ------

Personal injury or death can result from sudden machine movement.

Sudden movement of the machine can cause injury to persons on or near the machine.

To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine.

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------ WARNING! ------

Personal injury can result from contact with hot hydraulic oil and from contact with hydraulic oil that is under high pressure.

Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. The hydraulic oil pressure must be released before any service on the hydraulic system is performed or serious personal injury could occur.

Verify that all of the work tools have been completely lowered to the ground. Release the hydraulic oil pressure at the hydraulic tank through the breaker relief valve when the breaker relief valve is cool enough to touch with your bare hand. Verify that the hydraulic oil is cool before you begin to remove any hydraulic components or hydraulic lines.

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NOTICE

Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.

Refer to Special Publication, NENG2500, "Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids.

Dispose of all fluids according to local regulations and mandates.


Note: Use the information in the reference to prepare the machine for this test. Also, use the information in the reference to relieve any hydraulic pressure that may be in the hydraulic system.

The procedure requires two people.

ReferenceFor the correct procedure to prepare the machine for this test, refer to Testing and Adjusting, "Machine Preparation for Troubleshooting" for the machine that is being serviced.

ReferenceFor the correct procedure to relieve any hydraulic oil pressure that may be in the hydraulic system, refer to Testing and Adjusting, "System Pressure - Release" for the machine that is being serviced.

Table 1
Required Tools    
Part Number     Description     Qty    
1U-5796     Pressure Differential Gauge Group     1    
8T-0855     Pressure Gauge (0 to 600 psi)     1    
8T-0861     Pressure Gauge (0 to 8700 psi)     1    
177-7861     Hose As     2    
4C-4892     Fitting Group     1    

The margin pressure is the difference between the pump discharge pressure and the load signal pressure.

Travel Pump

  1. Position the machine on level ground.



    Illustration 1g01052558

    Location of the switch for the hood on early machines




    Illustration 2g01162235

    Location of the switch for the hood on later machines




    Illustration 3g01074453

  1. Open the hood for the engine compartment.

    Note: The switch for the hood is located underneath the right armrest on early machines. On later machines, the switch for the hood is located on the right hand console.

  1. Shut off the engine.

  1. Release all the hydraulic system pressure.



    Illustration 4g01078095

    Main Hydraulic Pump

    (1) Pressure tap for the travel pump. (2) Pressure tap for the implement pump. (3) Travel pump. (4) Implement pump.

  1. Connect one end of a 177-7861 Hose Assembly to pressure tap (1) for travel pump (3) .



    Illustration 5g00932554

    (5) Pressure gauge. (6) High pressure port. (7) Pressure differential gauge group. (8) Low pressure port. (9) Hose assembly (pump output pressure). (10) Hose assembly (signal pressure).

  1. Attach the unconnected end of the hose assembly to high pressure port (6) of 1U-5796 Pressure Differential Gauge Group (7) .

  1. Install 0 to 60000 kPa (0 to 8700 psi) pressure gauge (5) onto high pressure port (6) of pressure differential gauge group (7) .

    Note: Pressure gauge (5) will measure the pump output pressure.

  1. Connect a separate 177-7861 Hose Assembly to low pressure port (8) of pressure differential gauge group (7) .



    Illustration 6g01078097

    (3) Travel pump. (11) Pressure tap.

  1. Attach the unconnected end of hose assembly (10) to pressure tap (11) on travel pump (3) .

  1. Start the engine.



    Illustration 7g00786054

    Cab Compartment on early machines




    Illustration 8g01162814

    Cab Compartment on later machines

  1. Shift the hydraulic lockout into the UNLOCKED position. All implements should now be operable.

  1. Warm the hydraulic oil to normal operating temperature. Normal operating temperature is 55 ± 5°C (130 ± 10°F).

  1. Move the engine speed dial to high idle. The high idle speed for the machine that is being serviced is 2200 ± 80 RPM.

  1. Slowly press the right travel pedal in order to steer the machine to the left.

  1. Record the margin pressure.

    Note: The margin pressure is indicated on pressure differential gauge group (7) .

  1. The needle on pressure differential gauge group (7) will bounce between readings, but the margin pressure should stabilize at 2200 kPa (320 psi).

  1. Release the right travel pedal.



    Illustration 9g00936758

    Main Implement Pump

    (12) Adjustment screw for the travel pump. (13) Adjustment screw for the implement pump.

  1. If the margin pressure is not correct, an adjustment to the adjustment screw for the margin pressure must be made. The adjustment screw for the margin pressure is located on the piston pumps.

  1. Move the engine speed dial to low idle. Stop the engine.

  1. Adjust setscrew (12) in order to adjust the pump margin pressure setting for travel pump (3) . Turn the setscrew clockwise in order to increase the margin pressure. Turn the setscrew counterclockwise in order to decrease the margin pressure.

  1. Repeat Steps 10 through 20 until the margin pressure is correct.

  1. Relieve the hydraulic pressure. See the reference at the start of this procedure for the correct method.

  1. Remove all the hydraulic test equipment. Connect all the lines.

Implement Pump

  1. Release all hydraulic system pressure.



    Illustration 10g01078095

    Main Hydraulic Pump

    (1) Pressure tap for the travel pump. (2) Pressure tap for the implement pump. (3) Travel pump. (4) Implement pump.

  1. Connect the 177-7861 Hose Assembly to pressure tap (2) for output of implement pump (4) .



    Illustration 11g00932554

    (5) Pressure gauge. (6) High pressure port. (7) Pressure differential gauge group. (8) Low pressure port. (9) Hose assembly (pump output pressure). (10) Hose assembly (signal pressure).

  1. Attach the unconnected end of the hose assembly to high pressure port (6) of 1U-5796 Pressure Differential Gauge Group (7) .

  1. Install 0 to 60000 kPa (0 to 8700 psi) pressure gauge (5) onto high pressure port (6) of pressure differential gauge group (7) .

    Note: Pressure gauge (5) will measure the pump output pressure.

  1. Connect a separate 177-7861 Hose Assembly to low pressure port (8) of pressure differential gauge group (7) .



    Illustration 12g01078103

    (4) Implement pump. (14) Pressure tap.

  1. Attach the unconnected end of hose assembly (10) to pressure tap (14) on implement pump (4) .

  1. Start the engine.



    Illustration 13g00786054

    Cab Compartment on early machines




    Illustration 14g01162814

    Cab Compartment on later machines

  1. Shift the hydraulic lockout into the UNLOCKED position. All the implements should now be operable.

  1. Warm the hydraulic oil to normal operating temperature. Normal operating temperature is 55 ± 5°C (130 ± 10°F).

  1. Move the engine speed dial to high idle.

  1. Slowly move the right joystick in order to raise the boom.

  1. Record the margin pressure.

    Note: The margin pressure is indicated on pressure differential gauge group (7) .

  1. The needle on pressure differential gauge group (7) will bounce between readings, but the margin pressure should stabilize at 2200 kPa (320 psi).

  1. Lower the boom to the ground.



    Illustration 15g00936758

    Main Hydraulic Pump

    (12) Adjustment screw for the travel pump. (13) Adjustment screw for the implement pump.

  1. If the margin pressure is not correct, an adjustment to the adjustment screw for the margin pressure must be made. The adjustment screw for the margin pressure is located on the piston pumps.

  1. Move the engine speed dial to low idle. Stop the engine.

  1. Adjust setscrew (13) in order to adjust the pump margin pressure setting for implement pump (4) . Turn the setscrew clockwise in order to increase the margin pressure. Turn the setscrew counterclockwise in order to decrease the margin pressure.

  1. Repeat Steps 7 through 17 until the margin pressure is correct.

  1. Relieve the system hydraulic pressure. See the reference at the start of this procedure for the correct method.

  1. Remove all the hydraulic test equipment.

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