CP54B, CS54B and CS64B Vibratory Soil Compactors Propel System Propel System Troubleshooting Caterpillar


Propel System Troubleshooting
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1.1. Operational Checks
2.1. Probable Causes of Problems in the Propel System
3.1. Electrical Circuit For The Propel Brake Interlock

------ WARNING! ------

Do not operate or work on this machine unless you have read and understand the instructions and warnings in the Operation and Maintenance Manual. Failure to follow the instructions or heed the warnings could result in injury or death. Contact your AVSpare dealer for replacement manuals. Proper care is your responsibility.


------ WARNING! ------

Escaping fluid under pressure, even a pinhole size leak, can penetrate body tissue, causing serious injury, and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury.

Always use a board or cardboard when checking for a leak.


------ WARNING! ------

Personal injury can result from rotating and moving parts. Stay clear of all rotating and moving parts.

Never attempt adjustments while the machine is moving or the engine is running unless otherwise specified.

The machine must be parked on a level surface and the engine stopped.

Attach a "Do Not Operate" or similar warning tag to the start switch and controls before servicing, repairing, or making adjustments to the machine.


------ WARNING! ------

Personal injury or death can result from sudden machine movement.

Sudden movement of the machine can cause injury to persons on or near the machine.

To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine.


------ WARNING! ------

Personal injury can result from hydraulic oil pressure and hot oil.

Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system.

Make sure all of the attachments have been lowered, and the oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.



NOTICE

Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the machine. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.

Refer to Special Publication, NENG2500, "AVSpare Tools and Shop Products Guide", for tools and supplies suitable to collect and contain fluids in AVSpare machines.

Dispose of all fluids according to local regulations and mandates.


Operational Checks

Note: The checks during operation can be used to find leakage in the system. These checks can also be used to find a bad valve, a bad pump, or a bad motor. Travel speed can be used to check the condition of the propel motors and the pump.

Operate the machine in each direction and in all speeds.

  • Watch the drum and the wheels.

  • Starting and stopping operations should be progressive.

  • The drum and the wheel rotation should work smoothly with no jerky motion.

  • Check for noise from the pump and drive motors.

  • Check for the sound of the relief valves that are opening. The opening pressures of the relief valves are given in Relief Valve (Piston Pump) - Test and Adjust and Relief Valve (Charge) - Test and Adjust of this module.

  • After selecting the travel speed of the compactor, the forward and reverse motion should be identical.

Probable Causes of Problems in the Propel System

Problem

The machine starts to move very slowly when the propel lever is moved out of neutral in either forward or reverse.

Probable Cause

  • Low charge pressure.

  • The control orifices in the piston pumps are plugged.

  • The oil is too viscous and/or the oil is too cold.

  • The charge filter is plugged.

  • The hydraulic oil level is low.

  • The control valve is malfunctioning.

Problem

The propel system engages very suddenly when the operator moves the propel control lever.

Probable Cause

  • The orifices are missing from the piston pumps.

  • The shuttle valve that is in a flushing valve is sticking.

  • The servo valve spool in one or both of the propel pumps is sticking.

Problem

The propel system operates in one direction only.

Probable Cause

  • The pump servo piston has failed.

  • One of the multifunction valves is faulty.

  • The control valve in one of the propel piston pumps is faulty.

Problem

The machine does not stop when the propel control lever is returned to neutral.

Probable Cause

  • The pump servo piston has failed.

  • The rocker arm section of the pump swashplate assembly has failed.

  • The neutral adjustment of the servo valve is incorrect.

  • The linkage rod between the directional control valves is incorrectly adjusted.

Problem

The parking brake does not release when the parking brake button is pulled up.

Probable Cause

  • The parking brake switch has failed.

  • There is a malfunctioning piston seal in the brake group.

  • The propel interlock valve in the drum propel pump is faulty.

  • There is a fault in the electric circuit.

  • The neutral start switch has failed.

  • The neutral start relay has failed.

  • Low charge pressure.

  • The brake relay has failed.

  • The coil on a propel interlock valve has failed.

  • The propel interlock valve is faulty.

  • The relief valve on the gear pump is damaged or incorrectly adjusted.

  • Failure of the gear pump.

Problem

The parking brake does not engage when the parking brake button is pushed down.

Probable Cause

  • The parking brake switch has failed.

  • The brake relay has failed.

  • The brake discs are worn.

  • There is a pinched brake line.

  • The propel interlock valve in the drum pump is faulty.

  • There is a fault in the electrical circuit.

Problem

There are external oil leaks from either of the piston motors.

Probable Cause

  • Motor case pressure is too high.

  • There is a restriction in the oil return line to the hydraulic oil tank.

  • There are damaged seals due to pressure peaks, use of unapproved hydraulic oil, or an incorrect tightening torque.

Problem

The oil in the propel system overheats.

Probable Cause

  • An incorrect type of oil is used in the hydraulic circuit.

  • The oil cooler is internally restricted.

  • The radiator and/or the oil cooler is externally restricted.

  • There is failure in the fan drive system.

  • There is low charge oil flow.

  • The operating pressures are exceeding the relief pressures due to mechanical problems.

  • The thermal bypass valve is faulty.

  • The relief pressures in the propel pump are set lower than POR pressure.

Problem

Low charge pressure (Neutral).

Probable Cause

  • The hydraulic oil level is low.

  • The charge filter in the propel system is in the bypass mode.

  • There is an inadequate flow of oil from the gear pump.

  • There is excessive leakage from the motor case.

  • There is excessive leakage from the pump case.

  • The seal on the parking brake is leaking.

Problem

Low charge pressure (Propelling).

Probable Cause

  • There is excessive leakage from the motor case.

  • There is excessive leakage from the pump case.

  • The hydraulic oil level is low.

  • The charge filter in the propel system is in the bypass mode.

  • There is an inadequate flow of oil from the gear pump.

  • There is excessive leakage from the motor case.

  • There is excessive leakage from the pump case.

  • The seal on the parking brake is leaking.

Electrical Circuit For The Propel Brake Interlock

When the parking brake switch is placed in the ON position, the axle and the drum valves (propel interlock) are de-energized. This will prevent the pumps from stroking. Oil flow to the parking brake is stopped and the parking brake is applied. The brake interlock valves will not de-energize when the propel lever is out of the neutral position.

Problem

You are unable to propel the machine.

Probable Cause

  • The brake fuse is open.

  • The neutral start switch is improperly adjusted or The neutral start switch has failed in the open position.

  • Relay "P9" has failed.

  • An open circuit exists in the brake interlock valves and/or the harness for the neutral start switch.

  • The parking brake switch has failed.

  • An open circuit exists in the harness for the interlock system.

  • The propel interlock valve coil has failed.

Problem

The parking brake does not engage.

Probable Cause

  • Relay "P6" has failed.

  • The parking brake switch has failed.

  • A short circuit exists in the harness for the interlock system.

Problem

The Machine moves when the parking brake switch is moved to the OFF position and the propel control lever is out of NEUTRAL position.

Probable Cause

  • The neutral start switch is failed in the closed position.

  • Relay "P7" has failed.

  • An open circuit exists in the harness for relay "P7".

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