JLG 1850SJ, Service And Maintenance Manual, Page: 421 / 712

SECTION 5 - BASIC HYDRAULIC INFORMATION & HYDRAULIC SCHEMATICS
3121619 5-169
Trouble Shooting
Table 5-43. Troubleshooting
Low or No Flow From Gear Pump
Item Description Action
1. Check oil level in reservoir. Description Insufficient oil to supply gear pump. Fill reservoir to proper level.
2. Check input spline condition. Input shaft broken or stripped. Repair or replace gear pump.
3. Check pressure at pump inlet. Recommended inlet pres-
sure: 0.8 to 3.0 bar absolute. 0.6 Minimum at cold start. Clogged suction filter or inlet screen. Replace filter or clean suction screen.
4. Check condition of gear faces and bearing blocks. Scored bearing block and gear faces will reduce pump effi-
ciency. Repair or replace gear pump.
5. Check bushings. Overpressure of gear pump will cause idler gear bushing to
fail. Repair or replace gear pump.
Excessive Noise
Item Description Action
1. Check oil level in reservoir. Excessive air will cause cavitation sound. Fill reservoir to proper level .
2. Check inlet line for leaks. Excessive air will cause cavitation sound. Repair inlet line.
3. Check pressure at pump inlet. Recommended inlet pres-
sure: 0.8 to 3.0 bar absolute. 0.6 Minimum at cold start. Lower than normal inlet pressure causes excessive pump
noise. Return inlet pressure to recommended levels.
External Leakage
Item Description Action
1. Check for pinched o-rings or backup ring seal. Pinched seal will allow leakage. Replace pinched seal.
2. Check pressure seals. Damage to pressure seals is typically caused by reduced
stack-up in the pump assembly. This may be due to under-
torqued assembly fasteners, or more commonly is attrib-
uted to excessive wear on the bearing blocks. Reduced stack-
up will affect seal efficiency possibly to the point of seal
extrusion. Inspect condition of bearing blocks. If they are found to be
worn, repair or replace the pump.
If bearing blocks are not worn, replace pressure seals and re-
torque pump assembly fasteners.