SECTION 4 - HYDRAULICS
4-22 – JLG Lift – 3121642
4.10 GEAR PUMP
Gear Pump Priming
The gear pump is mounted with the suction hose up. Air
trapped in this area can cause an air lock on start up. during
this period, the pump is running dry, which can cause gear
wear, which affects the volumetric efficiency of the pump.
To prime the pump:
1. Fill the hydraulic tank to the full mark.
2. Using a 2" wrench, loosen the suction hose fitting at the
gear pump. The hose fitting does not need to be
removed, just loosened enough to let the air escape.
3. When oil leaks at the hose end, re-torque the hose end
to 115 lb-ft ( Nm). The pump is primed and the machine
is ready to start.
1. Outlet Port, 7/8-14UNF-2B
SAE #10
2. Inlet Port, 1-1/16-12UN-2B
SAE #16
Figure 4-23. Gear Pump
Table 4-8. Gear Pump Specs
Rotation (Viewing Drive End) Clockwise
Displacement
0.878 in/rev
(14.4 cc/rev)
Max Rated Speed 3500 rpm
Rated Pressure
3625 psi
(250 bar)
Minimum Speed at Rated Pressure 1000 rev/min
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