JLG Skytrak 6036 Service Manual page 188

Trouble
Tandem Pump Fails to
Deliver Fluid
Cylinder Fails to Move
When Control Valve is
Actuated
Cylinder Movement is
Jerky
Cylinder Movement is
Sluggish
Cylinder Piston Rod
Drifts or Creeps
Relief Valve Doesn't
Hold Pressure Setting
Directional Control
Valve Does Not Return
9-75
Probable Cause
Fluid viscosity is too heavy
to pick up prime
Worn, broken or stuck
parts in pump
Faulty hose
Damaged cylinder
Defective main control
valve
Air trapped in cylinder or in
hydraulic line
Binding of cylinder rod or
piston
Rod seal installed improp-
erly
Binding of base end or rod
end bearing
Defective counterbalance
cartridges (Hoist cylinders)
Control valve not fully en-
gaged
Internal leakage or binding
in cylinder
Worn piston seals
Internal leaking in control
valve
Tube is out-of-round
Spring broken or has taken
a "set"
Poppet stuck due to dirt or
deposits
Excessive clearances be-
tween valve body and pop-
pets
Remedy
Check working temperature and service and
change fluid in system if necessary
Repair tandem pump (para 9.4.1).
Repair or replace hose.
Repair or replace cylinder as required (para 9.2).
Inspect and repair as required (para 9.3.1).
Inspect fluid for foam and bubbles. Check and
tighten connections. Bleed cylinder and lines as
required.
Repair or replace cylinder (para 9.2).
Disassemble cylinder and repair (para 9.2).
Repair or replace bearing in applicable compo-
nent
Replace cartridges (9.2.1).
Engage control valve fully. Be sure that valve
linkage and drain lines are unrestricted.
Repair or replace cylinder (para 9.2).
Install cylinder seal kit (para 9.2).
Inspect control valve and install seal kit (para
9.3.1).
Replace tube and install seal kit (para 9.2).
Disassemble valve, inspect and clean. Install
seal and spring kit (para 9.3.6).
Clean all foreign material from parts and check
operation (para 9.3.6). Poppets must slide freely
in valve body. If poppets slide freely, install seal
and spring kit. If poppets still stick, replace valve.
Excessive clearances will cause internal leakage.
Replace relief valve.
Model 6036 S/N 9B0499 and Before
Section 9. Hydraulic System