797F Off-Highway Truck: Relief Valve (Hoist)

Table 1
Tools Needed	Qty
6V-2198 Extension Cable ⁽¹⁾	2
143-4066 Pressure Sensor ( 51700 kPa (7500 psi)) ⁽¹⁾	2
6V-4144 Coupler Assembly ⁽¹⁾	2
6V-3079 Pressure Hose Assembly ⁽²⁾	2
6V-4143 Coupler Assembly ⁽²⁾	4
8T-0860 Pressure Gauge ( 40000 kPa (5800 psi)) ⁽²⁾	2

^( 1 )	These parts are needed only when Caterpillar dataview tool gp is used.
^( 2 )	These parts are needed only when gauges are used.

Note: Refer to the Hydraulic System Systems Operation/Testing and Adjusting, "Using Caterpillar DataView to Determine Test Data" in order to learn more about connecting Caterpillar DataView (DataView) to the sensors.

(1) Pressure tap for the oil that is flowing from the rear two sections of the gear pump for the hoist and for the brake cooling
(2) Hoist relief valve for the rear two sections of the gear pump for the hoist and for the brake cooling
(3) Hoist relief valve for the front two sections of the gear pump for the hoist and for the brake cooling
(4) Pressure tap for the oil that is flowing from the front two sections of the gear pump for the hoist and for the brake cooling
(5) Control valve for the hoist and for the brake cooling
(6) Hoist control valve(7) Electrical connections

Lower the dump body. Stop the engine.

Connect a 6V-4144 Coupler Assembly to a 143-4066 Pressure Sensor (0 to 51700 kPa (0 to 7500 psi)). Connect this assembly to pressure tap (1) on control valve (5) for the hoist and for the brake cooling. Use a 6V-2198 Extension Cable to connect the sensor to one of the analog inputs on DataView.Note: If gauges are used, connect a hose assembly with an 8T-0860 Pressure Gauge (0 to 40000 kPa (0 to 5800 psi)) to pressure tap (1) on control valve (5) .

Connect another 6V-4144 Coupler Assembly to a 143-4066 Pressure Sensor (0 to 51700 kPa (0 to 7500 psi)). Connect this assembly to pressure tap (4) on control valve (5) for the hoist and for the brake cooling. Use a 6V-2198 Extension Cable to connect the sensor to one of the analog inputs on Dataview.Note: If gauges are used, connect another hose assembly with an 8T-0860 Pressure Gauge (0 to 40000 kPa (0 to 5800 psi)) to pressure tap (4) on control valve (5) .


Location of the engine speed sensor

Refer to the Hydraulic System Systems Operation/Testing and Adjusting, "Using Caterpillar DataView to Determine Test Data" in order to connect the engine speed sensor to DataView.Note: The engine speed is required in order to understand the graph from the datalogger after the test is performed.

Set up the datalogger.Note: Be sure to set the timer on the datalogger in order to allow enough time to start the engine and complete the test.

Start the engine. Operate the dump body repeatedly until the temperature of the hydraulic oil is above 38 °C (100 °F).

Lower the dump body. Stop the engine. Disconnect electrical connections (7) to the four proportional solenoid valves on hoist control valve (6) .Note: Hoist relief valve (2) and hoist relief valve (3) allow oil to flow to the brake cooling system if the system pressure increases above the pressure setting of the relief valves. When electrical connections (7) on the proportional solenoid valves are disconnected, the spools in hoist control valve (6) remain closed. Therefore, the oil that is flowing from the gear pump for the hoist and for the brake cooling is forced to open hoist relief valve (2) and hoist relief valve (3) when the hoist control is in the RAISE position.

Start the datalogger on Dataview.

Start the engine. Operate the engine at HIGH IDLE.

Hold the hoist control to the RAISE position for 15 seconds.Note: The dump body will not raise.
Note: If gauges are used, check the pressure on the gauges that are connected to pressure tap (1) and pressure tap (4) .

Stop the engine.

Stop the datalogger. Download the file from the datalogger. View the graph of the data. Observe the pressure of the relief valve for the head end of the hoist cylinders when the engine is at high idle.Note: The pressure setting of the hoist relief valves is 22050 ± 345 kPa (3200 ± 50 psi) with full pump flow at HIGH IDLE.

If the pressure setting of hoist relief valve (2) or hoist relief valve (3) needs adjusting, stop the engine.


Hoist relief valve (8) Locknut(9) Setscrew

Loosen locknut (8) of the hoist relief valve that needs adjusting.

With a flat head screwdriver, rotate setscrew (9) clockwise by 1/4 turn in order to increase the pressure. Rotate setscrew (9) counterclockwise by a 1/4 turn in order to lower the pressure. Each turn of setscrew (9) changes the pressure approximately 1500 kPa (215 psi).