JLG 1850SJ Service And Maintenance Manual page 386

SECTION 5 - BASIC HYDRAULIC INFORMATION & HYDRAULIC SCHEMATICS
Oil level in reservoir
Control orifices
Control screens
Charge pressure with pump in neutral
Pump charge relief valve
Charge pump inlet filter
Charge pump
System pressure
Charge check / HPRVs
Input to control
Optional control cutoff valve
Item
Reservoir oil level
Aeration of the oil/pump inlet vacuum
Cold oil
Pump inlet vacuum
Shaft couplings
Shaft alignment
Charge/system relief valves
5-134
Table 5-37. System will not operate
Item
Insufficient hydraulic fluid to supply system loop. Fill reservoir to proper level.
Control orifices are blocked.
Control screens are blocked.
Low charge pressure insufficient to recharge sys-
tem loop.
A pump charge relief valve that is leaky, contami-
nated, or set too low will depressurize the sys-
tem.
A clogged filter will under supply system loop.
A malfunctioning charge pump will provide
insufficient charge flow.
Low system pressure does not provide enough
power to move load.
Defective charge check / HPRVs cause system
pressure to be low.
Input to control module is operating improperly. Repair or replace control.
Control cutoff valve coil not energized.
Table 5-38. System noise or vibration
Low oil level leads to cavitation.
Air in system decreases efficiency of units and con-
trols. Air in system is indicated by excessive noise in
pump, foaming in oil, and hot oil.
If oil is cold, it may be too viscous for proper function
and pump cavitates.
High inlet vacuum causes noise/cavitation.
A loose input shaft to prime mover coupling will
cause excessive noise.
Misaligned input and prime mover shafts create
noise.
Unusual noise may indicate sticking valves. Possible
contamination.
Description
Clean control orifices.
Clean or replace control screens.
Measure charge pressure with the pump in neu-
tral. If pressure is low, go to next step.
Adjust or replace pump charge relief valve as nec-
essary.
Inspect filter and replace if necessary.
Repair or replace the charge pump.
Measure system pressure. Continue to next step.
Repair or replace charge check / HPRVs.
Ensure charge pressure to control via port X7. If
none, confirm control cutoff valve coil is ener-
gized. If still no pressure, repair or replace control
cutoff valve.
Description
Fill reservoir.
Find location where air is entering into the system
and repair. Check that inlet line is not restricted and
is proper size.
Allow the oil to warm up to its normal operating
temperature with engine at idle speed.
Check that inlet line is not restricted and is proper
size. Check filter and bypass switch.
Replace loose shaft coupling.
Correct misalignment.
Clean/replace valves and test pump. May be a nor-
mal condition.
Action
Action
3121619