JLG 534D-10 - Manual (Page 105)

6.7 534D-9, 534D-10 & 544D
Hydrostatic Drive Pump
Another test to determine the loss of charge pressure is
to cap off lines to the drive motors (3). Reinstall hoses
from previous test. Install low pressure gauge (1,000 psi
- 69 bar) on the charge pressure test port. Check each
motor separately. Start at the left rear motor. Remove the
hoses to the motor at the tubes and plug with ORS #12
plugs. Cap the motor work ports also to prevent dirt from
entering the motor with ORS #12 caps. Start the machine
and observe the gauge for charge pressure. Engage
drive forward and reverse against the park brake and
observe the gauge for charge pressure simultaneously.
Record the findings. If charge pressure recovers, the
motor is defective. If the charge pressure does not
recover, repeat test for the right rear motor.
Isolate the front drive motor from the circuit if the rear
motors are not defective. To isolate it will require two
blocking plates. Install these plates between the front
drive motor work ports and the drive hoses (4). Remove
the flange halves and place the blocking plates on the
ports and reinstall the hoses and the flanges. Again, start
the machine and observe the pressure gauge for charge
pressure. If the charge pressure recovers, the motor is
defective. To confirm, check charge pressure with drive
against the park brake. Charge pressure should remain
at 380 psi (26 bar).
The charge pump efficiency also needs to be checked if
previous tests prove inconclusive. Check charge flow out
of T1 port on the side of the pump (5). At 950 RPM, there
should be 4 GPM of flow. At 2400 rpm, there should be
12 GPM of flow. Disconnect run tee and plug. Measure
charge pump flow out of fitting against above
specification. The flow readings are checked at
480 psi (33 bar). If the test is positive on flow, proceed to
the next step.
To check internal leakage of the main pump, block off
ports A and B (6) at the main pump. If the drive motors
have already been isolated, continue testing. Install two
high pressure (10,000 psi - 689 bar) gauges, hoses and
adapters in drive pump ports Ma and Mb. Start machine
and operate at low idle. If the pump is good, pressure at
the Ma and Mb test ports should read 380 psi (26 bar).
Adjust relief valve to see if pressure responds. Engage
forward drive with park brake set, raise engine speed to
high idle and record drive pressure and charge pressure.
Repeat this procedure for reverse. Drive pressure should
be 6300 psi (434 bar) in each direction. Charge pressure
should remain at 380 psi (26 bar) and rise to
approximately 480 psi (33 bar) near full throttle.
3
4
5
6
6