JLG 18RS Service Manual - Manual (Page 125)

SECTION 5 - HYDRAULICS
3121284 – JLG Lift – 5-35
General Adjustment Practices
This section offers instruction on inspection and adjustment of
pump components. Read through the entire topic before
beginning a service activity. Refer to Pressure measurements,
for location of gauge ports and suggested gauge size.
STANDARD PROCEDURES
CONTAMINATION CAN DAMAGE INTERNAL COMPONENTS AND VOID YOUR
WARRANTY. TAKE PRECAUTIONS TO ENSURE SYSTEM CLEANLINESS WHEN
REMOVING AND REINSTALLING SYSTEM LINES.
1. With the prime mover off, thoroughly clean the outside
of the pump.
2. If removing the pump, tag each hydraulic line. When you
disconnect hydraulic lines, cap them and plug each
open port to prevent contamination.
3. Ensure the surrounding area is clean and free of contam-
inants like dirt and grime.
4. Inspect the system for contamination.
5. Check the hydraulic fluid for signs of contamination: oil
discoloration, foam in the oil, sludge, or metal particles.
6. If there are signs of contamination in the hydraulic fluid,
replace all filters and drain the hydraulic system. Flush
the lines and refill the reservoir with the correct filtered
hydraulic fluid.
7. Before re-installing the pump, test for leaks.
Charge Pressure Relief Valve Adjustment
Refer to Figure 5-38., Charge Pressure Adjustment.
1. Install a 50 bar [1000 psi] pressure gauge in charge pres-
sure gauge port M3. Install a 10 bar [100 psi] gauge at
case pressure port L2, or L4. Operate the system with the
pump in neutral (zero displacement) when measuring
charge pressure.
2. The table below shows the acceptable pump charge
pressure range for some nominal charge relief valve set-
tings (refer to model code located on serial number
plate). These pressures assume 1800 min-1 (rpm) pump
speed and a reservoir temperature of 50°C [120°F], and
are referenced to case pressure.
NOTE: Listed pressures assume a pump speed of 1800 min-1 (rpm)
and charge flow of 26.5 l/min [7 US gal/min]. At higher
pump speeds or higher charge flows the charge pressure
will rise over the rated setting.
3. Rotate the adjusting screw clockwise to increase the set-
ting; counter clockwise to decrease it. Subtract the case
pressure reading to compute the actual charge pressure.
NOTE: Pressure change per turn is dependant on charge flow
entering pump.
4. While holding the adjusting screw, torque locknut to 17
N•m [13 lbf•ft].
5. When you achieve the desired charge pressure setting,
remove the gauges and plug the ports.
Table 5-8. Charge Pressure Ranges
Model Code Actual Charge Pressure*
20 20 bar [290 psi ] ± 1.5 bar [21.8 psi]
24 24 bar [348 psi] ± 1.5 bar [21.8 psi]
26 26 bar [377 psi] ± 1.5 bar [21.8 psi]
30 30 bar [435 psi] ± 1.5 bar [21.8 psi]