374D Excavator Hydraulic System Swing Pump - Test - Positive Flow Control Caterpillar

Introduction

This procedure will test the flow control of the swing pump by the swashplate solenoid. A specific amperage applied to the solenoid will result in a specific amount of flow from the swing pump.

Required Tools

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".

4. Attach 311-1362 Vacuum Cap onto the hydraulic tank. Attach an air supply hose onto the assembly. Apply 276 to 414 kPa (40 to 60 psi). This procedure will pull a vacuum on the hydraulic system.
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   Illustration 1	g02175794
   Tool layout for swing pump (1) 8T-4193 Bolt (2) 5P-8077 Half Flange (3) Delivery line (swing pump) (4) Swing pump (5) 1P-3705 Rectangular Seal (6) 7I-7132 Cover (9) 174-4356 Pump Adapter (10) 2S-4078 O-ring Seal (11) 174-4360 90 degree Elbow (12) 3J-1907 O-ring Seal (13) 9S-4191 Plug (14) 4C-5093 Nipple Assembly (15) 4C-5094 Coupler As (16) 4C-6461 Coupling (17) 5P-0477 Sleeve (18) 5P-0202 Hose (19) 9U-6807 45 degree Coupling (20) 6K-6307 O-Ring Seal (21) 4C-9910 Portable Hydraulic Tester (Flow meter) (22) 9U-5229 Union (23) 2P-1415 Collet (24) Return port (return line for hydraulic cooling package)

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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, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products. Dispose of all fluids according to local regulations and mandates.

5. Disconnect delivery line (3) from swing pump (4).

6. Install seal (5), half flanges (2) and cover (6) to the end of delivery line (3) by using bolts (1).

7. Remove the plug from return port (24).

8. Install the tools in accordance with the flow meter tool layout. Refer to Illustration 1.

9. Install multitach on the engine to monitor engine speed.
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   Illustration 2	g02176077
   (25) Service connector

10. Connect Cat ET to service connector (25). Cat ET will be used to input a fixed amperage to the swashplate solenoid of the swing pump.
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    Illustration 3	g02175919
    Swing Pump (bottom view) (4) Swing pump (28) Solenoid

11. Install an ammeter at the electrical connector at the swashplate solenoid to measure the amperage that is sent from the machine electronic control module to the swashplate solenoid of the swing pump.
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    Illustration 4	g02176085
    Lower compartment under the main control valve Pilot manifold (27) Pressure tap

12. Connect a 34,450 kPa (5,000 psi) pressure sensor to pressure tap (27) at the pilot manifold.
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    Illustration 5	g02175833
    Swing pump (28) Pressure tap

13. Connect a 41,368 kPa (6,000 psi) pressure sensor to pressure tap (28) at the swing pump to monitor the delivery pressure of the swing pump.

Test Procedure

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To prevent personal injury or equipment damage from failure of the hydraulic test equipment or associated circuit components because of blocked pump flow, make sure that the test equipment valves are fully open before starting the engine.

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To prevent personal injury and/or equipment damage from failed lines or components while the hydraulic test equipment is returned to the open flow position, slowly open the hydraulic test equipment valve while monitoring the pump flow. If pump flow does not increase as the valve is opened, shut the engine off and determine what is preventing the pump from upstroking.

1. Start the engine.
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   Illustration 6	g01919740
   Monitor and keypad (A) Engine speed (B) Gain/Response (C) AEC switch (D) Gain/Response switch

2. Place the machine controls at the following settings:

   • Engine speed dial "10"

   • AEC switch OFF

   • Gain/Response "AVS" (normal mode)

   Refer to Testing and Adjusting, "Engine Performance - Test (Engine Speed)" for engine rpm settings.

3. Place the hydraulic lockout lever in the UNLOCKED position.

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

5. Check the pilot oil pressure at pressure tap (27). The pressure reading should be 4120 ± 100 kPa (600 ± 15 psi). If the pilot oil pressure is not within the specification, adjust the pilot relief valve. Refer to Testing and Adjusting, "Relief Valve (Pilot) - Test and Adjust" for information concerning the adjustment of the pilot relief valve.

6. Enter a value of "0.5 A" in Cat ET for the swashplate solenoid at the swing pump. Check the ammeter. If the value at the ammeter is not 450 mA, increase or decrease the "0.5 A" value until the ammeter reads 450 mA.

   Note: Step 6 provides a fixed amperage of 450 mA to the swashplate solenoid to measure the output flow of the swing pump while the swing pump swashplate is maintained at a constant position.

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   Illustration 7	g02176095
   (21) Portable hydraulic tester (flow meter) (31) Multitach group (32) Valve

7. Slowly, turn valve (32) on portable hydraulic tester (21) clockwise until the delivery pressure is 6850 kPa (1000 psi). Use the pressure reading at pressure tap (28) to monitor the delivery pressure of the swing pump.

8. Measure the flow rate.

Worksheet

Illustration 8	g02176898
I-Q Characteristic Curve

Note: Specifications for flow rates are based on an engine speed of 1800 rpm. To attain more accurate test results, measured flow should be corrected with the following calculation.

Note: Flow measurements must be done only during pressure rise.