TM 5-3805-260-24Test 15: Pump Flow at High Pressure (test rpm)1. Run the engine at test rpm.2. Slowly close the load valve to get 1000 psipressure.3. Write down the oil temperature and flow rate(gpm).Test 16: Pump Flow at Low Pressure (1/2 test rpm)1. Run the engine at 1/2 test rpm.2. Open the load valve to get 100 psi pressure.3. Write down the oil temperature and flow rate(gpm).Test 17: Pump Flow at High Pressure (1/2 test rpm)1. Run the engine at %/2 test rpm.2. Slowly close the load valve to get 1000 psipressure.3. Write down the oil temperature and flow rate(gpm).Make a comparison of the test data with the data onChart B for the specific machine under test. Theinformation on Chart B is the maximum for bestperformance.TroubleshootingPROBLEM: Percent of flow loss for Test 15 is 10% orMORE; for Tests 4 and 5 it is 15% or MORE.PROBABLE REASON:Pump is worn and there is leakage in controlvalve and/or cylinder.RECOMMENDATION FOR ACTION:Do the Blocked Cylinder Tests to find leakagerate in control valve and/or cylinder. Install a newor rebuilt pump.PROBLEM: Percent of flow loss for Test 15 is 0 to10%; for Tests 4 and 5 it is 15% or MORE.PROBABLE REASON:Pump is in good condition, but there is leakage incontrol valve and/or cylinder.RECOMMENDATION FOR ACTION:Do the Blocked Cylinder Tests to find leakage rate incontrol valve and/or cylinder.PROBLEM:For vane pumps only, the percent offor Test 15 is 10% or MORE. Flowdifferential for Test 15 is higher thanthe flow differential for Test 17 by 0 to2 gpmPROBABLE REASON:Pump is worn.RECOMMENDATION FOR ACTION:If flow loss is found to be too high for machineapplication, install a new or rebuilt pump.PROBLEM: For vane pumps only, the percent of flowloss for Test 15 is 10% or MORE. Flow differential forTest 15 is higher than the flow differential for Test 17 by0 to 2 gpm.PROBABLE REASON:A. Oil aeration (low oil level, hydraulic oil that is notthe correct type, air leak in the suction line for the pump,oil leaks in the tank such as failure of seals or looseconnections).B. Pump cavitation (restriction in the suction line forthe pump, oil viscosity that is not correct).RECOMMENDATION FOR ACTION:Do Tests 18 through 25 to find if the reason is aeration orcavitation.Pump Test for Aeration and CavitationTests 18 through 25: Aeration and CavitationTests These eight tests are similar. Do the tests asfollows:1. Open the manual load valve fully before startingthe diesel engine.2. Run the engine at rpm indication shown on ChartB.3. Slowly close the manual load valve to get 1000psi pressure.4. Write down the flow rate (gpm) and the oiltemperature.5. Then run the engine at the next rpm indicationshown on Chart B (Test 20: rpm indication onChart, Test 21: rpm indication on Chart, etc.)while keeping the adjustment of the manual loadvalve at 1000 psi pressure.6. Write down the flow rate (gpm) and oiltemperature for each test.2-121
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