Charge Pump Flow Test (Using Tester With Pressure Gauges and Flow Meter)
The charge pump flow test should be performed if a hy-
draulicproblemisidentifiedthataffectsboththesteering
and lift circuits.
IMPORTANT: The charge pump is a positive dis-
placement pump. If the flow control valve on the
tester is fully closed, transmission damage can oc-
cur.
NOTE: The charge pump provides make--up oil for in-
ternal hydrostat components before flow is available for
the steering and lift circuits. Flow measured in this test
will be less than total charge pump output.
9. Watch tester pressure gauges carefully while slowly
closingtheflowcontrolvalveuntilpressuregaugereads
500 PSI (34.5 bar).
1.
perature by operating the machine for approximately 10
minutes.
Make sure hydraulic oil is at normal operating tem-
10.Flow gauge reading should be at least 1 GPM (3.8
LPM).
11.
Open flow control valve on tester and turn offengine.
2.
Parkmachineonalevelsurfacewiththecuttingdeck
Record results of hydraulic flow test.
(or implement) lowered and P.T.O. switch off. Make sure
engine is off. Set the parking brake and block the front
wheels to prevent machine movement.
12.If
pressureof500PSI(34.5bar)orflowof1GPM(3.8
LPM) could not be achieved, check the following:
A. Perform the charge pressure test (see Charge
Pressure Test in this section). Also, a dynamic
charge pressure test can be performed to identify ifa
worn or damaged hydrostatic transmission exists.
3.
Read Precautions For Hydraulic Testing.
CAUTION
B. Perform the implement relief pressure test (see
Implement Relief Pressure Test in this section).
Before opening hydraulic system, operate all
hydraulic controls to relieve system pressure
and avoid injury from pressurized hydraulic oil.
C. Inspect the condition of the charge pump gerotor
and internal housing (See Charge Pump Service in
the Sauer--Danfoss (Sundstrand) 15 Series Service
Manual at the end of this chapter).
4.
Placeadrainpanunderthetransmission.Thorough-
ly clean the area around the transmission charge pump
outlet(pressure)fitting(Fig.23).Disconnectthehydrau-
lic hose from the outlet fitting.
D. The general condition of the transmission’s pis-
ton pump and piston motor might be suspected of
wear and inefficiency.
IMPORTANT: Make sure that the oil flow indicator
arrow on the flow meter is showing that the oil will
flow from the pump, through the tester and to the
hydraulic hose.
13.Disconnect testerfromthetransmission andhydrau-
lic hose. Reconnect hydraulic hose to the transmission
fitting. Check hydraulic oil level in reservoir (front axle).
5.
Connect inlet hose of tester with pressure gauges
4
3
and flow meter to the transmission charge pump outlet
(pressure) fitting. Connect the tester outlet hose to the
hydraulic hose disconnected from the transmission fit-
ting in step 5.
6.
Make sure that the flow control valve on the tester is
2
fully open. Also, make sure that traction pedal and lift
valve are in neutral and that the parking brake is en-
gaged.
FRONT
1
7.
draulic leakage from test connections and correct be-
fore proceeding with test.
Start engine and run at idle speed. Check for any hy-
Figure 23
1.
2.
Hydrostatic transmission
Hydraulic hose
3.
4.
O--ring
Outlet fitting
8.
tachometer to verify that engine speed is correct.
Run engine at full speed (3200 + 50 RPM). Use a
Hydraulic System
Page 5 -- 26
Groundsmaster 3280--D/3320
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