725 and 730 Articulated Trucks Machine Systems Caterpillar

The hoist system operates slowly.

Possible Causes

1. The oil level is incorrect.
   • Refer to Operation and Maintenance Manual, SEBU7814, "Hoist, Steering, and Brake System Oil Level - Check".

2. The oil is not at operating temperature.
   • Refer to Systems Operation, Testing and Adjusting, "General Information".

3. There is a problem with the electrical connections between the hoist control, the ECM and the Pilot control actuators.

4. The pilot pressure to the hoist control valve is incorrect.
   • Refer to Systems Operation, Testing and Adjusting, "Pressure Reducing Valve (Hoist Pilot Pressure) - Test and Adjust".

5. There is a problem with the hoist control valve.

   1. The spool is not moving to the correct position. This could be due to damage or contamination within the hoist control valve or the pilot control actuators.
      • Refer to Systems Operation, Testing and Adjusting, "Hoist Control Valve - Test".

6. There is a problem with the piston pumps for the hoist.
   • Refer to Systems Operation, Testing and Adjusting, "Piston Pump ( Steering, Hoist) - Test and Adjust".

   • Refer to Systems Operation, Testing and Adjusting, "Piston Pump ( Brake, Hoist, Fan) - Test and Adjust".

7. There is mechanical damage to one or both of the hoist cylinders. This could include damage to the seals.
   • Refer to Disassembly and Assembly, RENR3447 for information on the hoist cylinders.

There is no response when the RAISE position is selected or the LOWER position is selected.

1. There is a problem with the electrical connections between the hoist control, the ECM and the Pilot control actuators.

2. The pilot pressure to the hoist control valve is incorrect.
   • Refer to Systems Operation, Testing and Adjusting, "Pressure Reducing Valve (Hoist Pilot Pressure) - Test and Adjust".

3. There is a problem with the hoist control valve.

   1. The spool is not moving to the correct position. This could be due to damage or contamination within the hoist control valve or the pilot control actuators.
      • Refer to Systems Operation, Testing and Adjusting, "Hoist Control Valve - Test".

4. There is mechanical damage to one or both of the hoist cylinders. This could include damage to the seals.
   • Refer to Disassembly and Assembly, RENR3447 for information on the hoist cylinders.

The dump body will not maintain the raised position

1. There is a problem with the electrical connections between the hoist control, the ECM and the Pilot control actuators.

2. There is a problem with the hoist control valve.

   1. The spool is not moving to the correct position. This could be due to damage or contamination within the hoist control valve or the pilot control actuators.
      • Refer to Systems Operation, Testing and Adjusting, "Hoist Control Valve - Test".

   2. The springs, which move the spool to the HOLD position, are damaged.

3. There is mechanical damage to one or both of the hoist cylinders. This could include damage to the seals.
   • Refer to Disassembly and Assembly, RENR3447 for information on the hoist cylinders.