Toro Groundsmaster 3500 30807 Service Manual page 95

Traction Circuit Testing − Charge Pressure Test:
The charge pressure test is the first in a series of tests
recommended to determine traction circuit perform-
ance. A charge pressure drop of more than 20% indic-
ates an internal leak in the piston pump/hydrostat.
Continued unit operation can generate excessive heat,
cause damage to seals and other components in the hy-
draulic system, and affect overall machine perform-
ance.
Special Equipment Required:
S Pressure Gauge
S Flow Meter with Pressure Gauge that has at least
an 18 GPM (68 LPM) capacity.
S Phototach (non−contact tachometer).
1. Park machine on a level surface with the cutting units
lowered and PTO switch off. Make sure engine is off and
the parking brake is engaged.
2. Read Precautions for Hydraulic Testing in this
chapter.
3. Make sure that traction pedal is adjusted to the neu-
tral position.
4. Disconnect hose to the rear hydraulic fitting on the
piston pump coming from the hydraulic manifold port
(CHG) (Fig. 24).
5. Install a T−connector and pressure gauge between
the fitting and disconnected hose.
6. Disconnect hose from the lower hydraulic fitting on
the engine side of the hydrostat (Fig. 25).
7. Install tester in series with the pump and the discon-
nected hose. Make sure the tester flow control valve is
fully open.
8. Attach a heavy chain to the rear of the machine frame
and an immovable object to prevent the machine from
moving during testing.
9. Chock the wheels to prevent wheel rotation during
testing.
10.Start engine. Move throttle to full speed (Diesel en-
gine = 3220 + 50 RPM, Gas engine = 3420 + 30 RPM).
11. Make sure hydraulic fluid is at normal operating tem-
perature by operating the machine for approximately 10
minutes.
12.Verify with a phototach that the pump speed is ap-
proximately 2850 RPM.
Groundsmaster 3500
1. Hydraulic fitting
1
1. Lower hydraulic fitting
13.Record reading on pressure gauge from CHG mani-
fold port. Charge pressure (without load) should read
from 150 to 200 PSI (10.3 to13.8 Bar). If charge relief
pressure specification is not met, consider the following:
A. Gear pump (P2) is faulty (steering/lift/sidewinder
circuit performance will also be affected). Test gear
pump (P2) flow (see Gear Pump (P2) Flow Test in
this chapter).
B. The piston pump charge relief valve is faulty. Re-
pair or replace the piston pump charge relief valve
(see Piston Pump Service in this chapter).
14.Sit in the operator's seat, release the parking brake,
and slowly depress the forward traction pedal until 1000
to 1500 PSI (68.9 to 103.4 Bar) is reached on the flow
meter pressure gauge.
15.Record reading on pressure gauge from CHG mani-
fold port (under load). Charge pressure (under load)
should not drop more than 20% when compared to
charge pressure (without load) recorded in step 13.
If specifications are not met, perform Piston Pump/Hy-
drostat (P3) Flow and Traction Relief Pressure Test as
outlined in this chapter.
16.Release traction pedal, move throttle to low speed
and turn the engine off.
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1
Figure 24
2. Piston pump
2
Figure 25
2. Piston pump
Hydraulic System
2