M314F and M316F Wheeled Excavators Hydraulic System Margin Pressure - Test and Adjust Caterpillar

Introduction

Margin pressure is the difference between the pump discharge pressure and the load sensing signal pressure.

Specification

Required Tools

Illustration 1	g01623868
Tooling (B) 198-4240 Digital Pressure Indicator Gp

Machine Preparation

1. Clear all personnel from the machine and from the area around the machine.

2. Start the engine.
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   Illustration 2	g02449876
   Engine speed dial

3. Set the engine speed dial at "10".

4. Lower the left console.

5. Position the machine on level ground. Check the visibility and adjust the mirrors for the best vision close to the machine.

6. Fully depress the service brake pedal until the service brake pedal locks mechanically.

7. Increase the hydraulic oil temperature to 46° to 60° C (115° to 140° F).

8. Lower the stabilizers, the blade tip, and/or the implement to raise the front axle and the rear axle. This condition will allow the wheels to turn freely.

   Note: All tires must be fully off the ground.

9. Fully extend the bucket cylinder and place the bucket on the ground.

10. Stop the engine.

11. Raise the left console.
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    Illustration 3	g03722485
    Service connector on the right side of cab behind the seat

12. Connect tooling (E) to the service connector.
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    Illustration 4	g06009585

13. Attach Tooling (B2) 41,368 kPa (6,000 psi) pressure sensor to main pump pressure tap (1) and load sensing signal pressure tap (2)

14. Start the engine.
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    Illustration 5	g02449876
    Engine speed dial

15. Set the engine speed dial at "10".

16. Lower the left console.
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    Illustration 6	g02446738
    Power mode control button on the soft panel switch

17. Push down on the power mode control button to activate power mode.

    Note: The indicator light will be illuminated when power mode is activated.

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    Illustration 7	g02447036
    Automatic Engine Speed Control (AESC) as displayed on the programmable function key in the monitor.

18. Disable the automatic engine speed control through the monitor by pressing the programmable button.
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    Illustration 8	g03722432
    Hydraulic modulation switch on left joystick

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    Illustration 9	g06186138
    Hydraulic modulation aggressive mode (monitor display)

19. Select the hydraulic modulation mode as aggressive. Press the lower front switch on the left joystick to select the hydraulic modulation mode.

20. The air conditioning should be turned off for the following test.
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    Illustration 10	g02453444
    Transmission control button on the soft panel switch

21. Push down on the transmission control button to select Second GEAR.
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    Illustration 11	g02453447
    Creeper speed control button on the soft panel switch

22. Push down on the creeper speed control button to activate the creeper speed control.

    Note: The indicator light will be illuminated when the creeper speed control is activated.

Test Procedure

1. Release the service brake pedal.

2. Depress the travel speed pedal fully in the FORWARD position.

3. Start Electronic Technician

4. Select the Machine ECM and then select “OK”.

5. Select “Diagnostics” from the main menu.

6. Select “Diagnostic Tests”.

7. Select “Override Parameters”.

8. Select “Travel Pilot Solenoid Current Override” and set the current to 0.3 amp.

   Increase Travel Pilot Solenoid Current until transmission speed is equal to the specification in 1.

   Check the margin pressure on the pressure gauges with the travel pedal fully depressed.

   Note: Margin pressure is the difference between main pump pressure tap (1) and load sensing signal pressure tap (2).

9. Override the hydraulic modulation solenoid to 0.28 amp to set hydraulic modulation "Medium".

10. Check the margin pressure on the pressure gauges with the travel pedal fully depressed.

11. Override the hydraulic modulation solenoid to 0.38 amp to set hydraulic modulation "Low".

12. Check the margin pressure on the pressure gauges with the travel pedal fully depressed.

13. If margin pressure is not within the specification, perform the following "Adjustment Procedure" procedure to adjust the load sensing spool.

Adjustment Procedure

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Illustration 12	g06009594

1. Remove the cap and loosen the locknut on the adjustment screw for load sensing valve (3).

2. Turn the adjustment screw clockwise on load sensing valve (3) to increase the margin pressure. Turn the adjustment screw counterclockwise on load sensing valve (3) to decrease the margin pressure.

   Note: Turn the load sensing screw by a 1/8 turn to change the margin pressure by approximately 200 kPa (29 psi).

   Note: Always make the final pressure adjustments on the pressure rise.

3. Verify that the margin pressure is within specifications.

   Note: Refer to Table 1 for the correct pressure.

4. Tighten the locknut.

5. Install the cap.

   Note: If the cap was damaged during removal, replace the cap with a new orange cap.