REPAIR STEPS
SOLUTION
DIAGRAMS
PROBLEM
MI91.2139
11MAY98
REFER TO MP65.3455
Remove the return line from the pump. Push a jack control switch to
extend. If fluid flows out of the return line, replace the shuttle valve.
If no fluid flows from the return line, check voltage to the pump motor
while it is running. Low voltage will cause low pump pressure. Con-
nect a 5000 psi pressure gauge to the pressure fitting at the pump. If
there is less than 3000 psi while the pump is running, the pump should
be repaired. Remember to check the fluid level in the reservoir.
STAB.
LEFT
REAR
+
RIGHT
FRONT
FRONT
LEFT
H/V
+
+
+
RIGHT
REAR
SHUTTLE
VALVE
RETURN
LINE
CHECK
VALVES (4)
ADJUSTABLE
RELIEF
VALVE
PRESSURE
LINE
BREATHER
CAP
(OIL FILL)
PUMP
Part 4 continued
REFER TO MP85.3454
g. The jacks swing
vertical but retract
to the horizontal
position when the
H/V switch is re-
leased.
Push the H/V switch to VERTICAL. After the jacks are vertical, push
the MASTER SWITCH TO OFF before releasing the H/V switch. If
the jacks stay vertical, replace the H/V valve. If the jacks still retract
to the horizontal position, remove the return line from the pump. While
pushing the H/V switch to vertical, watch the return line. If fluid flows
from the return line, replace the bleed valve cartridge. If that does not
fix the problem, replace the H/V valve and the shuttle valve.
The actuators for 16,000 lb jacks can cause this problem. If the above
solution does not fix the problem, disconnect the hydraulic line to one
of the 16,000 lb jacks and cap the line. Retry the H/V switch. If the
jacks stay vertical, replace the actuator for the jack that is disconnect-
ed. If the jacks still retract, replace the actuator for the remaining 16,000
lb jack.
REFER TO MP65.3455
h. The red light for
a jack will not come
on when the jack
is vertical.
Ground the wire for that warning switch at the jack. If the light comes
on, check the ground for that switch. If the ground is OK, replace the
switch. If the light does not come on, unplug the warning light wire
Part 5
With an individual
jack control switch
pushed to
"EXTEND":
a. The pump does
not run.
If the vehicle is equipped with straight-acting jacks, refer to Part 4a.
Replace the use of the H/V switch with a jack control switch in the EX-
TEND position.
If the vehicle is equipped with kick-down jacks, it is assumed the pump
and relays work. Push the H/V switch to VERTICAL. If the pump runs,
but not when a jack control switch is pushed to EXTEND, the control
panel needs to be repaired or replaced. If the pump does not run when
the H/V switch is pushed, return to Part 4a of the Repair Steps.
STAB.
LEFT
REAR
+
RIGHT
FRONT
FRONT
LEFT
H/V
+
+
+
RIGHT
REAR
SHUTTLE
VALVE
RETURN
LINE
SEE ELECTRICAL
CONNECTION
DIAGRAM
CONTROL PANEL
CONTROL
PANEL
b. For straight-
acting jacks.
from the control panel. Use a test light connected to ground to ground
the pin for the red light that does not work. If the light comes on, the
harness wire is bad. If the light does not come on, replace the bulb or
have the control panel repaired.
The pump runs.
The jacks will not
extend or will ex-
tend but not pick
up the vehicle.
