349F and 352F Excavators Hydraulic System Caterpillar

Introduction

Negative flow control pressure flows to the regulators at the drive pump and the idler pump in order to control the output flow of the pumps. The proportional reducing valve for negative flow control regulates the amount of pilot pressure from the pilot pump and signal oil pressure from the main control valve that flows into the regulators of the main pumps. The proportional reducing valves for negative flow control are 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)"

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	g02404198
   Pressure taps for the proportional reducing valves (negative flow control) located in the pump compartment (1) Pressure tap for "NFC1" (2) Pressure tap for "NFC2"

4. Connect two 3447 kPa (500 psi) pressure sensors to the pressure taps for negative flow control. The proportional reducing valves for negative flow control of the drive pump and idler pump are located in the pump compartment.

Calibration Procedure

Note: This procedure is typical for both proportional reducing valves for negative flow control.

1. Start the engine.

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

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

4. Enter the service mode. Input the password "9992".
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   Illustration 3	g02540004

5. Select "Main Pump Flow Limit" from the "Calibrations" menu.
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   Illustration 4	g02540097

6. Select "NFC (Press Gauge Method)" for the appropriate valve from the "Main Pump Flow Limit" menu.

7. Press the OK key in order to start the calibration. The engine RPM will automatically increase to the equivalence of engine speed dial 10.

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 STICK OUT to the full out position and hold the joystick in this position.

   Note: If necessary, a BOOM RAISE function may be performed in place of STICK OUT.

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   Illustration 5	g02540199

10. Use the arrows to adjust the pressure until the pressure reading for the negative flow control valve is at 1500 ± 50 kPa (218 ± 7 psi). Press the OK key.

    Note: Use the arrows to scroll down to view the machine "Engine Speed", "Hydraulic Oil Temperature", "Pump #1 Outlet Pressure", and "Pump #2 Outlet Pressure".

11. Move the joystick for STICK OUT 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 STICK OUT to the full out position and hold the joystick in this position.

    Note: If necessary, a BOOM RAISE function may be performed in place of STICK OUT.

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    Illustration 6	g02540267

14. Use the arrows to adjust the pressure until the pressure reading for the negative flow control valve is at 3000 ± 50 kPa (435 ± 7 psi). Press the OK key.

    Note: Use the arrows to scroll down to view the machine "Engine Speed", "Hydraulic Oil Temperature", "Pump #1 Outlet Pressure", and "Pump #2 Outlet Pressure".

15. Move the joystick for STICK OUT to the NEUTRAL position.
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    Illustration 7	g02540302

16. If calibration was successful and no errors occurred, the display will indicate that the calibration is complete.
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    Illustration 8	g02540758

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.