824G Wheel Tractor, 825G Soil Compactor and 826G Landfill Compactor Hydraulic System Caterpillar

This test is designed to determine whether a pump is operating within design parameters. Presently, only a bench test is available for this purpose. This test should be performed only if all cylinder cycle times are too slow and the resolver network is functioning correctly.

For any pump test, the pump flow at 690 kPa (100 psi) will be larger than the pump flow at 6900 kPa (1000 psi) if the pump is operating at the same rpm. The pump flow is measured in L/min (US gpm).

The difference between the pump flow of two operating pressures is the flow loss.

Note: The values in the examples are not set values for any specific pump or for any specific pump condition. See the Specification for the pump flow of a new pump at 690 kPa (100 psi) and at 6900 kPa (1000 psi).

Table 1

Method of determining flow loss
	Pump flow at 690 kPa (100 psi)
-	Pump flow at 6900 kPa (1000 psi)
	Flow loss

Table 2

Example of determining flow loss
	217.6 L/min (57.5 US gpm)
-	196.8 L/min (52.0 US gpm)
	20.8 L/min (5.5 US gpm)

Flow loss that is expressed as a percentage of pump flow is used as a measure of pump performance.

Table 3

Method of determining percent of flow loss
Flow loss (L/min or US gpm)	×	100	=	Percent of flow loss
Pump flow at 690 kPa (100 psi)

Table 4

Example of determining percent of flow loss
20.8 L (5.5 US gal)	×	100	=	9.5%
217.6 L/min (57.5 US gpm)

Machine Test

Install a flow meter. Run the engine at high idle. Measure the pump flow at 690 kPa (100 psi) and at 6900 kPa (1000 psi). Use these values in the formula in Table 5.

Table 5

	Pump flow at 690 kPa (100 psi)
-	Pump flow at 6900 kPa (1000 psi)	×	100	=	Percent of flow loss
	Pump flow at 690 kPa (100 psi)

Bench Test

If the test bench can be run at 6900 kPa (1000 psi) and at full pump rpm, use the formula in Table 5 to determine the percent of flow loss.

If the test bench cannot be run at 6900 kPa (1000 psi) or at full pump rpm, run the pump shaft at 1000 rpm. Measure the pump flow at 690 kPa (100 psi) and at 6900 kPa (1000 psi). Use these values in the top portion of the formula in Table 6. For the bottom part of the formula, run the pump shaft at 2000 rpm. Measure the pump flow at 690 kPa (100 psi).

Table 6

	Pump flow at 690 kPa (100 psi)
-	Pump flow at 6900 kPa (1000 psi)	×	100	=	Percent of flow loss
	Pump flow at 690 kPa (100 psi) and at 2000 rpm

Reference: For more information about the specifications for the hydraulic pump, refer to Specifications, SENR5882, "980G Wheel Loader Hydraulic System".