TM 5-3805-260-24
2. Make an adjustment to the load valve to get 100 psi
pressure.
3. Write down the oil temperature and the flow rate
(gpm).
Test 25: Pump Flow at High Pressure (1/2 Test rpm)
1. Run the engine at ½ Test rpm.
2. Slowly close 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 Charts C1, C2, C3 for specific pump under test. The
information on Charts Cl, C2, C3 is for best pump
performance.
Troubleshooting
PROBLEM: Percent of flow loss for Test 23 is 10% or
more; for Test 4 through 7 it is more
than the percent shown in Chart A.
PROBABLE REASON:
Pump has a problem and leakage is in the
control valve, valve circuits and/or cylinders.
RECOMMENDATION FOR ACTION:
Find pump problem. Install a new or rebuilt
pump, if necessary. Do the Blocked Circuit Tests to find
leakage rate in the control valve, valve circuits and/or
cylinders.
PROBLEM:Percent of flow loss for Test 23 is 0 to
10%; for Tests 4 through 7 it is more than
the percent shown in Chart A.
PROBABLE REASON:
Pump is in good condition, but there is leakage
in control valve, valve circuits and/or cylinders.
RECOMMENDATION FOR ACTION:
Do the Blocked Circuit Tests to find leakage rate
in control valve, valve circuits and/or cylinders.
PROBLEM: Percent of flow loss for Test 23, Chart C2 is
15% or MORE; for Test 23, Chart C3, flow loss is 10% or
less.
PROBABLE REASON:
A large amount of elevator speed control valve
leakage.
RECOMMENDATION FOR ACTION:
Remove the speed control valve. Disassemble
the control valve and inspect the parts. Repair or replace
parts as necessary.
PROBLEM: Percent of flow loss for Test 23 is 10% or
MORE. Flow differential for Test 23 is
higher than the flow differential for Test
25 by 0 to 2 gpm.
PROBABLE REASON:
Pump is worn.
RECOMMENDATION FOR ACTION:
If flow loss is found to be too high for the
machine application, install a new or rebuilt pump.
PROBLEM: Percent of flow loss for Test 23 is 10%o
or MORE. Flow differential for Test 23 is
higher than flow differential for Test 25
by 2 gpm or MORE.
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 26 through 30 to find if the reason is
aeration or cavitation.
Pump Test for Aeration and Cavitation
Tests 26 through 30: Aeration and Cavitation Tests
These seven tests are similar. Do the tests as
follows:
1. Open the manual load valve fully, then start the diesel
engine.
2. Run the engine at the test rpm for Test 26.
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 test rpm (for Tests 27, 28, 29
and 30).
6. Write down the flow rate (gpm) and oil temperature
for each test.
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