Challenger 35, Challenger 45 and Challenger 55 Agricultural Tractors Implement, Steering and Brake Hydraulic Systems Caterpillar

This test is designed to determine whether a pump is operating within design parameters. This test should be run 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.

Table 1

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

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)

If the percent of flow loss is greater than 10%, the pump performance is inadequate.

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

Test on the Machine

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 following formula.

Table 5

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)

Test on the Bench

If the test bench can be run at 6900 kPa (1000 psi) and at full pump rpm, determine the percent of flow loss by using the above formula.

If the test bench can not 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 following formula. 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