JLG 340AJ Service Manual - Manual (Page 221)

SECTION 5 - HYDRAULICS
3121259 – JLG Lift – 5-63
Table 5-13. Neutral Difficult or Impossible to Find
Item Description Action
Input to pump control Input to control module is operating improperly Disconnect input and check to see if pump comes back to
neutral. If Yes, input fault, replace/repair external control-
ler. If No, go to next step.
Pump control neutral Neutral set improperly Shunt servo gauge ports M4 and M5 together with exter-
nal hose and see if pump comes back to neutral. If Yes: con-
trol neutral improperly set (see page 35). If no: balance
swashplate (see Mechanical neutral adjustment, page
37). If you still cannot set neutral, replace control.
Table 5-14. Sluggish System Response
Item Description Action
Oil level in reservoir Low oil level causes sluggish response Fill reservoir.
High pressure relief valves/ pressure limiter settings Incorrect pressure settings affects system reaction time Adjust or replace high pressure relief valves.
Low prime mover speed Low engine speed reduces system performance Adjust engine speed.
Charge pressure Incorrect pressure affects system performance Measure and adjust charge pressure relief or replace
charge pump.
Air in system Air in system produces sluggish system response Fill tank to proper level. Cycle system slowly for several
minutes to remove air from system.
Contaminated control orifices Control orifices are plugged Clean control orifices.
Contaminated control screens Control screens are plugged Clean or replace control screens.
Pump inlet vacuum Inlet vacuum is too high resulting in reduced system pres-
sure Measure charge inlet vacuum. Inspect line for proper siz-
ing. Replace filter. Confirm proper bypass operation.