PIN 9J2172 - Caterpillar

Introduction
This information includes the following test:
Margin PressureThis information includes the following adjustment procedure:
Adjustment Procedure (Margin Pressure)The fan pump margin pressure is the difference between the fan pump load sense pressure and the fan pump discharge pressure. When a load sense signal is sent to the pump, the controller adds some margin pressure on top of the signal.Required Tools
Illustration 1 g01879273
Tooling (D)
Table 3
Tool Item Qty Part Number Description
D 1U-5796 Pressure Differential Tool Gp
D2 4 6V-4143 Quick Connect Coupler
D3 3 6V-3965 Fitting
D4 1 6V-4144 Quick Connect Coupler
D5 1 8T-0859 Pressure Gauge
(0 to 25,000 kPa (0 to 3,600 psi))
D5 1 8T-0861 Pressure Gauge
(0 to 60,000 kPa (0 to 8,700 psi))
D6 1 8C-8431 Tee
D7 1 1U-5793 Oil Filter Pressure Differential Gauge Gp
D8 1 6V-0484 O-Ring Adapter Reference: Refer to Special Instruction, SEHS8979, "Component Identification and Calibration of the 1U5796 Differential Pressure Gauge Group" for more information on using Tooling (D).Test Preparation
Refer to Testing and Adjusting, "Machine Preparation for Troubleshooting".Refer to Testing and Adjusting, "System Pressure Release".
Ensure that the hydraulic oil temperature is at least at 60° C (140° F).
Illustration 2 g06097374
Move steering frame lock to the LOCKED position.
Engage the parking brake. Move the transmission direction selector to the NEUTRAL position.
Release system pressure.Test Procedure
Illustration 3 g06099460
Hydraulic service center
(1) Fan pump discharge pressure tap
(2) Fan pump load sense pressure tap
Turn off machine and release pressure in system.Note: The pressure will need to be released out of the system to attach the pressure gauge.
Attach a 0 to 25,000 kPa (0 to 3,626 psi) pressure gauge (D5) to the high-pressure port (D4) of pressure differential gauge group (D7).
Attach one end of hydraulic line (D1) to pressure tap (1). Pressure tap (1) is located in the hydraulic service center that is on the right side of the machine. Attach the other end of hydraulic line to the open end of the tee (D6) of pressure differential gauge group (D7).
Attach another hydraulic line (D1) to the fan pump load sense pressure tap (2). Attach the opposite end of hydraulic line (D1) to the low-pressure port (D8) of the pressure differential gauge group (D7).Note: Position pressure differential gauge group (D7) and hydraulic lines (D1) in order to prevent damage from any machine movement. Position the test equipment in order to allow a second technician to observe and record the pressure readings safely.
Record the pressure reading on pressure gauge (D7). The reading that is on pressure gauge (D7) is the margin pressure. Margin pressure is the difference between the fan pump pressure and the load sense pressure (2). The margin pressure should be 1,600 100 kPa (232 14 psi).Note: The pressure reading on pressure gauge (D5) is the fan pump discharge pressure.
If the margin pressure is correct, turn off the engine, and release the pressure to the hydraulics to disconnect the pressure gauges.
If the margin pressure is not correct, review the steps in the following section to adjust the pressure.Adjustment Procedure (Margin Pressure)
Illustration