JLG 1350SJP Service Manual - Manual (Page 356)

SECTION 5 - HYDRAULICS
5-32 – JLG Lift – 3121142
5.5 DRIVE PUMPS
Troubleshooting Procedure
To aid in troubleshooting, refer also to the pressure measuring
port connections for test gauge installation information as
shown on the hydraulic circuit diagram. Procedure assumes
proper gauges are installed. (Minimum gauges required: (2) 0-
6000 psi, (1) 0-3000 psi & (1) 0-1000 psi [{2} 0-415 bar, {1} 0-210
bar & {1} 0-70 bar]). This procedure was written to aid the trou-
bleshooter in following a logical approach to a hydraulic sys-
tem fault.
1. Transmission does not propel the machine, diesel
engine running properly
a. Is there oil in the reservoir?
No - Fill reservoir
Yes - If yes, proceed to step 1.b
b. Is the pump input shaft connected to the engine
flex plate or rear of forward pump?
No - Connect pump input shaft
Yes - If yes, proceed to step 1.c
c. Are the hydraulic hoses and tubing connected in
accordance with the hydraulic circuit diagram?
No - Correct the hoses/tubing
Yes - If yes, proceed to step 1.d
d. Is the pump direction of rotation correct? (clockwise
as looking at the shaft)
No - Fit pump having the correct direction of rota-
tion
Yes - If yes, proceed to step 1.e
e. Are there "O"-rings missing from fittings (as exam-
ple - suction leak), pinched hoses, broken tubing,
etc?
No - Proceed to step 1.f
Yes - Repair damage or fault
f. Are the electrical connectors/wiring intact and
secure to the pump control solenoids?
No - Repair damage or fault
Yes - If yes, proceed to step 1.g
g. Does the engine "labor" when attempting drive, are
the brakes released?
No - Proceed to step 1.h
Yes - Check brake release circuit, measure pressure
at port "MP" on Traction Control manifold
h. Are all four wheel drive planetary reduction gear-
boxes engaged?
No - Engage wheel drive(s)
Yes - If yes, proceed to step 2.a
2. Transmission does not propel the machine, diesel
engine running properly - Charge Pump/Relief Valve
a. Is there any charge pressure at port G or indicated
by measuring pressure at Ma and Mb?
No - Proceed to step 2.d
Yes - Proceed to step 2.b
b. Is the charge pressure at least 500 psi while running
at high engine speed?
No - Proceed to step 2.c
Yes - Proceed to step 3.a
c. Can the charge pressure be raised by removing dirt/
debris from charge relief poppet or by adding or
removing shims from the charge pressure relief
valve mounted in the second pump of the triple?
No - Proceed to step 2.d
Yes - Adjust pressure to 500 psi +50 psi, -0 psi (34.4
bar +3.4 bar, -0 bar)
NOTE: The propulsion circuit uses a hot oil flushing valve to
obtain brake release pressure. The hot oil flushing valve
cartridge (#120) is mounted in the Traction Control Mani-
fold. The flushing valve receives its oil from the "left side"
wheel drive pump; the middle pump of the triple. With the
engine running and propelling the machine forward or
reverse, the "hot oil flushing valve" and the brake release
pressure must be adjusted to 475 psi, +25 psi, -0 psi (32.7
bar, +1.7 bar, -0 bar), as set by adjusting pressure relief car-
tridge (#130). The brake release pressure must be 25 psi less
than the charge pump pressure. Measure pressure at port
"MP" using a 0-1000 psi (0 - 70 bar) pressure gauge.
d. Is the transmission pumps suction hose pinched
shut?
No - Proceed to step 2e
Yes - Repair damaged hose
e. Is the charge pump suction pressure/vacuum within
recommended limits? (0.8 bar absolute or 6.3 inches
of mercury)
No - Proceed to step 2.f
Yes - Proceed to step 2.g
f. Is the suction strainer inside the reservoir blocked,
clogged, restricted?
No - Proceed to step 2.g
Yes - Repair/replace with a clean suction strainer
g. Is the reservoir air breather blocked or restricted?
No - Proceed to step 2.h
Yes - Clean or replace air breather