Textron JACOBSEN GP400, Technical/Repair Manual

Page: 225 / 354

HYDRAULICS
4252490-Rev A 6-33
6
Figure 6-24: Cutting Units Circuit Test—Right Reel
Motor Blocked
8. Block each side of rear wheels using suitable wheel
blocks.
9. Bypass seat switch and release park brake.
NOTE
Verify engine rpm is within specification (3400 rpm ± 50)
to ensure accurate hydraulic test results.
10. Start engine and run at full throttle (3400 rpm ± 50).
11. Use the flow meter to warm the hydraulic oil. Turn
flow meter valve (4) until a reading of 1500 psi (103
bar) or 50% of the relief valve rating is reached.
Warm oil to 120–150° F (49–65° C); open valve fully
after operating temperature is reached.
12. Engage mow switch.
13. Read and record the cutting units circuit no load flow.
14. Slowly close flow meter valve (4) until pressure
reaches 2200 psi (152 bar) or 75% of the relief valve
rating is reached. Read and record the cutting units
circuit loaded flow.
15. Open flow meter valve (4), disengage mow switch,
and stop engine.
16. Calculate cutting units circuit leakage.
(Step 13 – Step 14 / Step 13 x 100 = Leak
Percentage)
Is cutting units circuit leakage 10% or less?
YES The cutting units circuit is good. Proceed to
“Reel Motors Test” on page 6-36.
NO Proceed to next question.
Is cutting units circuit leakage 11–20%?
YES The cutting units circuit is marginal.
Additional testing is required. Proceed to
“Gear Pump Test” on page 6-33.
NO Proceed to next question.
Is cutting units circuit leakage 21% or more?
YES Test individual components in cutting units
circuit for leakage. Proceed to “Gear Pump
Test” on page 6-33.
Gear Pump Test
See Figures 6-25 through 6-27.
IMPORTANT
• Performing this test will isolate the gear pump
from the rest of the cutting units circuit.
• This test works together with the cutting units
circuit test, reel valve unit test, and reel motors
test to isolate a problem with the cutting units
circuit.
!
WARNING
1. Park the mower safely. (See “Park Mower Safely” on
page 1-6.)
2. Before performing this test, perform cutting units
circuit test, leaving flow meter connected as outlined.
TN3097
The hydraulic system is under pressure, and the
oil will be hot.
• Always relieve pressure in the hydraulic
system before performing service.
• Failure to follow appropriate safety
precautions may result in death or serious
injury.
Required Tools and Materials
• Flow Meter
• -8 ORFS Test Hose 4000 psi (276 bar)
• -8 ORFS Tee Fitting
• -8 ORFS Blocking Disk