JLG 450A Service And Maintenance Manual page 100

SECTION 3 - TROUBLESHOOTING
TROUBLE
Pump not delivering oil.
Function sluggish during operation. (System
pressure too low.)
System(s) operate erratically.
Auxiliary hydraulic pump inoperable.
3-16
Table 3-5.Hydraulic System - Troubleshooting
PROBABLE CAUSE
Restricted suction line.
Air entering system through broken line or fitting.
Broken pump drive shaft/pump coupling.
Main relief valve set too low.
Pump section not delivering sufficient oil.
Main relief valve stuck in open position.
Oil viscosity too low.
Leak in component, line or fitting.
Scored valve spool; scored cylinder.
Amperage too low on controller.
Low sequence pressure.
Low pilot pressure.
Wrong/defective spool in drive section.
Shuttle balls leaking in proportional valve.
Low voltage in electrical system.
Sticking or binding valve spools, pistons.
AUXILIARY HYDRAULIC SYSTEM.
Circuit breaker open.
Engine is running.
Check valve in system leaking.
Battery requires charging or will not hold a
charge.
– JLG Lift –
REMEDY
Clean, repair, or replace line.
Repair or replace line or fitting.
Repair or replace pump/pump coupling.
Note: Any time pump or pump drive coupling
is removed coat pump and drive coupling
splines with Lithium Soap Base Grease (TEX-
ACO CODE 1912 OR EQUIVALENT).
Reset valve as required.
Repair or replace pump section or pump.
Clean, repair, or replace valve. (Check system oil
for contamination.)
Drain system and replace with recommended oil.
(Refer to Hydraulic Oils.)
Repair or replace component, line or fitting.
Replace valve; replace cylinder.
Correctly adjust controller.
Reset valve as required.
Reset valve as required.
Repair or replace drive section.
Repair or replace valve.
Correct low voltage problem.
Clean, repair, or replace components as
required.
Determine and correct cause; reset circuit
breaker.
Shut down engine.
Repair or replace check valve.
Charge or replace battery as required.
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