374D Excavator Hydraulic System Main Pump (Flow) - Test - Constant Horsepower Flow Control Caterpillar

Introduction

This test measures individual pump flow at the pump. Each pump is tested individually for output flow at specified pressures. The pump that is not being tested is not under load and the pump remains at low-pressure standby.

Note: Before starting main pump flow tests, check the monitor for normal operation. If no faults are present, perform the operational check. Refer to Testing and Adjusting, "Operational Checks".

Note: The engine, the fuel, or the working altitude may be the problem if the operational checks indicate that slow speed of an implement is common to both pump circuits.

Note: Perform the following procedures before testing the main pump flow.

• Set the pilot pressure to the specifications in Testing and Adjusting, "Relief Valve (Pilot) - Test and Adjust" for the machine.

• Set the main relief valve to specifications. Refer to Testing and Adjusting, "Relief Valve (Signal) - Test and Adjust" for the machine.

• Calibrate the power shift pressure. Refer to Testing and Adjusting, "Calibration" for the Machine Electronic Control System.

Required Tools

Illustration 1	g02571852
198-4240 Digital Pressure Indicator Gp

Illustration 2	g02535237
348-5430 Multi-Tool Gp

Machine Preparation

Note: Tool setup for the rear pump is similar to the front pump.

1. Position the machine on level ground.

2. Stop the engine.

3. Release the pressure in the hydraulic system. Refer to Testing and Adjusting, "Hydraulic 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.

Show/hide table



Illustration 3	g02173522
Tool layout for front pump (1) 8T-4193 Bolt (2) 5P-8077 Half Flange (3) Delivery line (front pump) (4) Delivery line (rear pump) (5) 1P-3705 Rectangular Seal (6) 7I-7132 Cover (7) Front pump (8) Rear pump (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)

5. Install the tools in accordance with the tool layout. Refer to Illustration 3.

6. Install the Multi-Tool Gp on the engine to monitor engine speed.

Show/hide table



Illustration 4	g02173524
Tool layout for front pump (right side view of main pumps) (A) Test hose (25) Load signal reduction manifold (26) Load signal line (27) 6V-4143 Coupler As (28) 6V-3014 Hose As (29) Pressure tap (power shift pressure) (30) Elbow (31) Pressure tap (load signal pressure) (32) 6V-9508 Face Seal Plug (33) 6V-8397 O-ring Seal (34) Hose for load signal (front pump) (35) 8T-8902 Tee (36) 3J-1907 O-ring Seal (37) 6V-3965 Nipple (38) Pressure tap (front pump delivery pressure) (39) 6V-9829 Cap As (40) Tee (41) Front pump regulator

7. Main pump pressure must be used to upstroke the pump when the flow meter is installed. Install the tools in accordance with the tool layout for the pump being tested. Refer to Illustration 4 for the tool layout for the front pump.

   Note: When testing the rear pump, the tool layout is similar.

   1. Disconnect load signal line (26) from tee (40) . Install a plug and O-ring seal to load signal line (26) . Install cap and O-ring seal to tee (40) .

   2. Disconnect hose (34) from elbow (30) . Install plug and O-ring seal.

   3. Install test hose (A) between pressure tap (38) and elbow (30) on the front pump regulator.

8. Connect a 34,450 kPa (5,000 psi) pressure sensor to pressure tap (29) to monitor power shift pressure.

9. Connect a 41,368 kPa (6,000 psi) pressure sensor to pressure tap (31) to monitor front pump delivery pressure.

Test and Adjust

Note: The front pump and the rear pump must be tested separately. Use the following procedure for testing both pumps.

Show/hide table

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.

Show/hide table

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.

Show/hide table



Illustration 5	g02173525
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 activation control lever in the UNLOCKED position.

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

5. Use the monitor in order to enter a fixed power shift pressure of 1870 ± 100 kPa (271 ± 15 psi).

   Note: Confirm the power shift pressure setting at pressure tap (29) .

Show/hide table



Illustration 6	g02731118
Portable hydraulic tester (flow meter) (21) Portable hydraulic tester (flow meter) (46) Valve

6. Turn valve (46) on portable hydraulic tester (21) clockwise. Record pump flow at each of the following pressures in Table 2. Use the pressure reading at pressure tap (31) to monitor pump delivery pressure.

Worksheet

Illustration 7	g02174876
P-Q characteristic curve (Power shift pressure at 1870 kPa (271 psi))

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.

Note: The pump flow changes approximately 33 L/min (8.7 US gpm) for each 100 kPa (15 psi) of power shift pressure.