1G-9335 Pressure Control Pilot (PCP) Performance Test Procedure Caterpillar

Problem:

The machine may exhibit propel related performance problems such as skewing or indexing when starting and stopping, drifting left or right or reduced maximum speed capability. The severity of these symptoms may vary as machine operating temperature increases.

Solution:

Monitor the left and right propel pump drive current inputs as follows:

1. Install two "Fluke" or equivalent multimeters to monitor the left and right propel pump forward EDC coil current. The left multimeter is to be connected in series with the left pump forward coil pin #10 at the propel MPC-10 40 pin connector. This can be accomplished by disconnecting the wire at pin #10 and installing a test wire in pin #10 that leads to one side of the multimeter and connecting the other side of the meter to the wire removed from pin #10 thus putting the meter in series with the left forward EDC coil. The right forward EDC coil current is to be monitored at the same time using pin #33 at the propel MPC-10 connector by putting a second meter in series with the right forward EDC coil similar to the procedure described for the left.

2. Calibrate the propel system, to rule out improper calibration, note the initial current values during "c12" auto calibration (typically 16-21 milliamps with the red lamp flashing). Record and clear any faults currently logged. If the multimeter leads are disconnected, at any time while the key is on, EDC faults will be logged. Monitor the forward EDC currents during calibration, read both meters while the red light is flashing. The left and right propel pump current values should be within 2 milliamps or less if the pump neutral adjustment is properly set. If the values exceed 2 milliamps neutral adjustment will be required. Refer to the procedure for "Piston Pump Neutral - Test and Adjust" in the Testing and Adjusting Manual for your machine. The AP-1000B/BG-260C will require the balance lines to be disconnected and plugged to allow accurate readings. The best propel performance is achieved when the forward calibration currents are closely matched.

3. With hydraulic oil temperature below 140(F the test may be conducted by driving the machine on a flat surface in a straight line or in the air on blocks, use the lowest speed range. The objective is to monitor, compare and record the forward current values (milliamps) driving the left and right propel pump EDC's at various speeds. The test will then be re-run at elevated hydraulic oil temperature and data compared. The machine must be driven in a straight line, observe the left pump current as you adjust the speed dial until 30 mA is observed then record the current (milliamps) driving the right pump. Record right pump (milliamps) data setting the left pump at 40 mA, 50 mA, 60 mA, 70 mA, 80 mA, 90 mA and max speed dial setting. The maximum difference in the current (milliamps) driving the left and right pumps should not exceed 10 mA at any of the test points. If the difference exceeds 10 milliamps, replace the PCP that requires the higher current level.

4.

NOTE: If testing the AP-1000B/BG-260C, with rear wheels in the air, the front wheels may drift slightly left or right due to steering valve leakage. This may cause the control system, due to steering sensor position, to vary the current to the left and right pumps resulting in false readings. Adjust the steering wheel as required to keep the front wheels straight during the test.

5. With hydraulic oil temperature below 140(F conduct a test similar to the test in step #3. The objective of this test is to monitor, compare and record the reverse current values (milliamps) driving the left and right propel pump EDC's at various speeds. MPC-10 pins #11 left reverse and #34 right reverse are used for this test. Conduct the test by setting the left pump at 30 mA, 40 mA, 50 mA, 60 mA, 70 mA, 80 mA, 90 mA and maximum speed dial and record the resulting current (milliamps) driving the right pump at each setting. The maximum difference in the current driving the left and right pumps should not exceed 10 mA at any of the test points. If the difference exceeds 10 milliamps replace the PCP that requires the higher current level.

6. The next test will be a repeat of step #3 and #4 with increased hydraulic oil temperature. The objective of this test is to determine if the PCP performance changes as the hydraulic oil temperature increases. To heat up the hydraulic oil run the engine at full speed and block the air flow into the oil cooler. Turn on the feeder system and adjust the conveyor ratio to slow the conveyors while the augers run at maximum RPM. The oil bypassing the conveyors will generate additional heat. Run the machine in this mode until the hydraulic temperature reaches 190(F. Repeat steps #3 and #4. Monitor and record the current required to drive the left and right pumps. If one of the PCP's malfunctions the current required will increase and the difference in current required to drive the left and right propel pumps will exceed 10 milliamps. If one PCP requires increased current and the other remained the same, the faulty PCP is the one with the increased current requirement. Replace the faulty PCP.

Forward Test

Reverse Test

COPYRIGHT 2000 CATERPILLAR ALL RIGHTS RESERVED