349F and 352F Excavators Hydraulic System Caterpillar

Introduction

The boom hydraulic circuit contains a regeneration circuit. This regeneration circuit allows the return oil from the head end of the boom cylinders to be supplied to the rod end of the boom cylinders during the BOOM DOWN operation. The proportional reducing valve (PRV) for the boom regeneration valve controls the amount of pilot pressure from the joystick to the boom down regeneration valve. The PRV for the boom regeneration valve is controlled by the machine ECM.

Preliminary Test

• Testing and Adjusting, "Relief Valve (Pilot) - Test and Adjust"

• Testing and Adjusting, "Solenoid Valve (Proportional Reducing) - Calibrate (Power Shift Pressure)"

• Testing and Adjusting, "Solenoid Valve (Proportional Reducing) - Calibrate (Negative Flow Control)"

Required Tools

Illustration 1	g02571852
Tooling (A) 198-4240 Digital Pressure Indicator Gp

Machine Preparation

1. Position the machine on level ground.

2. Stop the engine

3. Release the pressure in the hydraulic system. Refer to Testing and Adjusting, "System Pressure - Release".
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   Illustration 2	g02141845
   (1) Pressure tap for the proportional reducing valve (boom regeneration valve) (2) Pilot manifold (3) Panel

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   Illustration 3	g03396939
   Heavy lift solenoid (if equipped) (1) Pressure tap for the proportional reducing valve (boom regeneration valve) (2) Pilot manifold (3) Panel (4) Pressure tap for the heavy lift solenoid

4. Connect a 3447 kPa (500 psi) pressure sensor to the pressure tap for the boom regeneration valve. The pressure tap for the boom regeneration valve is located below the main control valve. The pressure tap can be accessed through panel (3).

Calibration Procedure

1. Start the engine.

2. Increase the hydraulic oil temperature to 55° ± 5°C (131° ± 9°F).

3. Place the hydraulic activation lever in the UNLOCK position.

4. Place the machine implements on the ground at maximum reach.

5. Enter the service mode. Input the password "9992".
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   Illustration 4	g02550247

6. Select "Boom Down Regen Valve" from the "Calibrations" menu.

7. Press the OK key in order to start the calibration. The engine RPM will automatically drop to the equivalence of engine speed dial 1.

8. Confirm the notes on the monitor display. Set up the test conditions in accordance with the instructions. Press the OK key.

9. Move the joystick for BOOM DOWN to the full down position and hold the joystick in this position.
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   Illustration 5	g02550277

10. Use the arrows to adjust the pressure until the pressure reading for the boom regeneration valve is at 500 ± 50 kPa (73 ± 7 psi). Press the OK key.

11. Move the joystick for BOOM DOWN to the NEUTRAL position.

12. Confirm notes on the monitor display. Set up the test conditions in accordance with the instructions. Press the OK key.

13. Move the joystick for BOOM DOWN to the full down position and hold the joystick in this position.
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    Illustration 6	g02550318

14. Use the arrows to adjust the pressure until the pressure reading for the boom regeneration valve is at 2500 ± 50 kPa (363 ± 7 psi). Press the OK key.

15. Move the joystick for BOOM DOWN to the NEUTRAL position.
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    Illustration 7	g02550516

16. If calibration was successful and no errors occurred, the display will indicate that the calibration is complete.
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    Illustration 8	g02550596

17. The "Error" screen will be displayed on the monitor if an error occurs. The process of calibration will not be saved and the process must be restarted.