The following procedure should be used in order to determine if there is a problem with the implement pump. Pump performance should be checked if the machine has slow implement movement or low digging power.
Machine Preparation
- Move the machine to a smooth horizontal location. Move away from working machines and personnel. Lower the implement to the ground.
- Allow only one operator on the machine. Keep all personnel away from the machine or in the view of the operator.
- Engage the parking brake.
Performance Test
Stall Test
The amount of oil flow that is produced by a pump will increase with the speed of the pump. First, verify that the pump is operating at the rated speed in order to test the performance of a pump. Perform the torque converter stall test in order to verify that a pump is operating at rated speed.
- Shift the transmission to the NEUTRAL position.
- Start the engine. Warm the transmission oil to normal operating temperature of approximately 65 ± 3°C (150 ± 5° F).
- Lower the implement to the ground.
- Ensure that the transmission neutralizer override switch is engaged.
- Fully depress the service brake pedal. Hold the brake pedal in the depressed position for the duration of the test.
- Release the parking brake.
- Place the transmission in FOURTH SPEED.
| NOTICE |
|---|
To make sure that the transmission oil does not overheat, do not keep the torque converter in a stall condition for more than 30 seconds. After the torque converter stall test, reduce engine speed to low idle, move the transmission control to neutral and increase the engine speed to approximately 1500 rpm to cool the oil. |
- Move the transmission direction control to the FORWARD position. In order to override the transmission neutralizer, the transmission direction control lever must be moved from the NEUTRAL position to the FORWARD position three times within 10 seconds.
- Increase the engine speed to high idle.
- Allow the engine speed to stabilize. Record the engine rpm.
- Reduce the engine speed to low idle.
- Shift the transmission to the NEUTRAL position.
The correct stall speed in fourth speed forward is 2200 ± 125 rpm.
Low stall speeds indicate a possible problem with engine performance . The stall speed should be corrected before the performance of the implement pump can be properly tested.
Implement Cycle Time
The speed of the implements is affected by the amount of oil flow that is produced by the implement pump. Check the implement cycle times in order to determine if there may be a problem with the implement pump.
- Perform the machine preparation for testing.
- Warm the hydraulic oil to normal operating temperature.
- Disengage the hydraulic lockout.
- Begin the test for the lift cycle time with the implement on the ground.
- Increase the engine speed to high idle.
- Pull the lift control lever back to the full RAISE position. Measure the lift cycle time. Record the lift cycle time.
- Raise the boom to the full raised position.
- Tilt the implement completely forward.
- Move the control lever to the full TILT BACK position. Measure the tilt cycle time. Record the tilt cycle time.
- Lower the implement to the ground.
- Reduce engine speed to low idle.
- Stop the engine.
| Cycle Times (Oil at normal operating temperature) | |
| Machine Function | Time in Seconds |
| Lift with empty implement | 6.0 ± 0.5 |
| Tilt Back | 2.0 ± 0.5 |
Compare the test results with the cycle times that are listed in Table 1. The implement pump should be working properly if the implement cycle times match the cycle times that are listed in Table 1.
If the cycle times are not correct for both the lift and tilt functions, one of the following conditions are present:
- The pressure setting of the main relief valve is not within specifications.
- The pump is not upstroking.
- The pump may have excessive wear.
The main relief pressure should be measured. If the main relief pressure is low, the cycle times should be retested after the main relief pressure has been corrected.
ReferenceFor more information on Testing and Adjusting the main relief valve, refer to the Service Manual module Testing and Adjusting, "Relief Valve (Main) - Test and Adjust" for the machine that is being serviced.
If the cycle time is slow for only one of the implement circuits, the circuit with slow cycle time should be tested for one of the following conditions:
- Low relief valve setting
- Leak in the circuit
- Control spool that is not shifting fully