TM 5-3805-260-24
Test 15: Pump Flow at High Pressure (test rpm)
1. Run the engine at test rpm.
2. Slowly close the load valve to get 1000 psi
pressure.
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 psi
pressure.
3. Write down the oil temperature and flow rate
(gpm).
Make a comparison of the test data with the data on
Chart B for the specific machine under test. The
information on Chart B is the maximum for best
performance.
Troubleshooting
PROBLEM: Percent of flow loss for Test 15 is 10% or
MORE; for Tests 4 and 5 it is 15% or MORE.
PROBABLE REASON:
Pump is worn and there is leakage in control
valve and/or cylinder.
RECOMMENDATION FOR ACTION:
Do the Blocked Cylinder Tests to find leakage
rate in control valve and/or cylinder. Install a new
or rebuilt pump.
PROBLEM: Percent of flow loss for Test 15 is 0 to
10%; for Tests 4 and 5 it is 15% or MORE.
PROBABLE REASON:
Pump is in good condition, but there is leakage in
control valve and/or cylinder.
RECOMMENDATION FOR ACTION:
Do the Blocked Cylinder Tests to find leakage rate in
control
valve
and/or
cylinder.
PROBLEM:For vane pumps only, the percent of
for Test 15 is 10% or MORE. Flow
differential for Test 15 is higher than
the flow differential for Test 17 by 0 to
2 gpm
PROBABLE REASON:
Pump is worn.
RECOMMENDATION FOR ACTION:
If flow loss is found to be too high for machine
application, install a new or rebuilt pump.
PROBLEM: For vane pumps only, the percent of flow
loss for Test 15 is 10% or MORE. Flow differential for
Test 15 is higher than the flow differential for Test 17 by
0 to 2 gpm.
PROBABLE REASON:
A. Oil aeration (low oil level, hydraulic oil that is not
the correct type, air leak in the suction line for the pump,
oil leaks in the tank such as failure of seals or loose
connections).
B. Pump cavitation (restriction in the suction line for
the pump, oil viscosity that is not correct).
RECOMMENDATION FOR ACTION:
Do Tests 18 through 25 to find if the reason is aeration or
cavitation.
Pump Test for Aeration and Cavitation
Tests 18 through 25: Aeration and Cavitation
Tests These eight tests are similar. Do the tests as
follows:
1. Open the manual load valve fully before starting
the diesel engine.
2. Run the engine at rpm indication shown on Chart
B.
3. Slowly close the manual load valve to get 1000
psi pressure.
4. Write down the flow rate (gpm) and the oil
temperature.
5. Then run the engine at the next rpm indication
shown on Chart B (Test 20: rpm indication on
Chart, Test 21: rpm indication on Chart, etc.)
while keeping the adjustment of the manual load
valve at 1000 psi pressure.
6. Write down the flow rate (gpm) and oil
temperature for each test.
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