Gradall 534D-10 Service Manual - Manual (Page 78)

Reason for Control Pressure Check
To ensure control pressure is correct for proper machine speed. For the machine to move at proper engine speed,
control pressure should match engine RPM.
Install a low pressure gauge (1,000 PSI), hose and adapter on the drive pump control pressure Ps port. Remove
the hose from port and plug. NOTE! Before starting, make sure the gauge can be observed in the operator’s cab
and apply the park brake. Start the engine and run at full throttle speed (2500-2700 RPM). With the pump in
neutral, the gauge should read 380 PSI. This may vary +/- 15 PSI.
(See Figure 13).
Use a tachometer to monitor engine speed. Start the engine and run at 1100 RPM. While watching the pressure
gauge, move the shift lever to the forward position. The gauge should read 100 PSI. Next repeat the test for
reverse. If the machine does not start to move at 1100 RPM engine speed in both directions equally at 100 PSI
control pressure, the stroking piston needs centered mechanically.
To check this adjustment, install a clean hose between control ports X1 and X2. They are lotated on the top of
the drive pump.
See Figure 14. Remove and plug control hoses from the top of the drive pump ports X1 and
X2. Install two high pressure (10,000 PSI) gauges, hoses and adapters in the drive pump ports MA and MB on
the side of the pump. Start the engine and operate at low idle. Observe the gauges. Pressure at MA port must
be equal to the pressure at MB port. If pressures are not equal, loosen locknut on stroking piston adjustment
and turn adjusting screw to equalize pressures. Tighten locknut to secure adjustment. Repeat this procedure with
low pressure (1,000 PSI) gauges to fine tune.
If the inching valve and forward/reverse valve work correctly but adjustment does not produce the desired
pressure change, replace the control pressure (DA) cartridge located on the left of the drive pump.
FIGURE 13
MAIN PUMP ASSEMBLY (SIDE VIEW)
VI. Control Pressure
Form No. 29633 3/97 534C-9 & 534C-10
HYDROSTATIC DRIVE PERFORMANCE CHECKS MANUAL
13