JLG 740AJ Service Manual - Manual (Page 216)

SECTION 3 - CHASSIS & TURNTABLE
3-164 – JLG Lift – 3121160
7. System retains pressure after shut-
down a. Solenoid valve stuck
b. Leak back from airline
a. Should be no power to solenoid valve
Valve stuck. Replace Pressure switch
faulty/replace
b. Check minimum pressure valve for
leak
8. Compressor stalls a. Belts slipping
b. Insufficient hydraulic system pres-
sure/flow. This can occur if another
hydraulically activated component is
used off same pump system. Activating
the secondary component may drop
hydraulic supply system pressure/flow
and leave insufficient for compressor.
NOTE - even a momentary drop in supply
hydraulic supply pressure/ flow may initi-
ate compressor blowdown to com-
mence.
c. Pressure relief valve set too low
d. Leak in seals on pressure relief valve
e. Air pressure set too high for hydraulic
system
f. Leak in solenoid valve cartridge
(directional flow control valve) on mani-
fold
g. Check over-pressure or over-temper-
ature
a. Readjust/tighten
b. Check setting on supply pressure
system relief valve. Check to ensure ade-
quate pressure/ flow. Check if other sys-
tems activated off same supply.
c. Check & reset
d. Remove & check seals or fit new valve
cartridge
e. Adjust pressure switch to reduce air
pressure.
f. Remove & check seals or fit new valve
cartridge.
Table 3-16. Air Compressor Troubleshooting
SYMPTOM PROBABLE CAUSE SOLUTION