FILM GP 3963356 - Caterpillar

Introduction
This Special Instruction is intended to provide information in order to test the cycle times for the boom, stick, and bucket for certain excavators. The problem that is identified is caused by a missing signal passage in the pump to cylinder spool. If the failure mode is found on the machine, inspect the spool and replace with the same part if the signal passage is missing. The missing signal passage will cause the function's precompensator to improperly engage, creating a failure mode that causes high-pressure drop between the pump and the cylinder which results in excessive pump pressure and slow cylinder speed.Solution
First perform the cycle time for the function according to the Testing and Adjusting Cylinder Speed instructions in Testing and Adjusting, KENR7985. If machine cycle times are within spec, proceed to the additional testing for this failure mode.If the cycle times are not within spec, first troubleshoot before proceeding to the additional tests. (Note: using the data log channels in the additional tests may help troubleshooting slow cycle time)Failure mode caused by the function's compensator improperly engaging can be seen when quickly changing direction of the cylinder. Testing for this failure mode consists of the following steps.Test
The following example is to test for intermittently slow Stick Out (cylinder retract). The same test procedure can be done for Stick In, bucket or boom.
Set up a data log for the specific function using the suggested channels.
Test A: Test/Data log the function for rapid change in direction.Example: Position the stick all the way out (cylinder completely retracted), then command 100% stick in. When the stick is near vertical, quickly change to command 100% stick out. Repeat this test for different switching points. Observe the speed of stick out.
Test B: Test/Data log the function for stopping before change in direction.Example: Position the stick all the way out (cylinder completely retracted), then command 100% stick in. When the stick is near vertical, stop the stick by returning the joystick back to neutral. Once the stick has stopped, command 100% stick out. Repeat this test for different switching points. Observe the speed of stick out.
Data Analysis: Review the data in order to determine the following during second direction of the two tests (stick out in the example above).
Primary Pump pressure (pump 1 for Boom/Bucket and Pump 2 for Stick)
Cylinder driving pressure (stick rod end for above example)
Pressure drop from pump to cylinder (pump 2 pressure minus Stick Rod pressure for example)
Are pump pressures during the direction being tested (stick out in this example) similar for Test A and Test B?
Is the pump to cylinder pressure drop during the direction being tested (stick out in this example) similar for Test A and Test B? For this example is the pressure drop from Pump 2 to Stick Rod End the same for both Test A and B.
Is the pump pressure within 4000 kPa (580 psi) or less than the cylinder driving pressure for Test A or Test B? (Is the difference of pump pressure