JLG sky trak mmv Service Manual page 182

Boom
a. Engine or Hydraulic Pump Failure
IMPORTANT: In the event of total loss of engine power
or hydraulic pump failure with an elevated load, properly
evaluate and deal with each situation on an individual
basis. Contact the nearest JLG Authorized Service Cen-
ter (ASC) or the JLG Service Department for specific
instructions.
Secure the vehicle until the situation has been properly
evaluated by following the procedures below:
1. Clear the area of any unnecessary personnel.
2. Block all four wheels.
3. Section off a large area under the boom with string
or tape to restrict any personnel from entering this
potentially dangerous area.
WARNING:
raised boom unless the boom is blocked up.
Always block the boom before doing any ser-
vicing that requires the boom to be up.
4. Temporarily block up or support the outer boom so it
cannot be lowered.
5. If the load can be removed safely, completely remove
the load from the carriage. If the load cannot be
removed, leave the load in place.
6. Place an Accident Prevention Tag on both the
ignition switch and steering wheel, stating that the
vehicle should not be operated. (Refer to Section
1.5, Accident Prevention Tag Usage .)
b. Hydraulic Line Failure
In the event of hydraulic line failure, follow these step-by-
step procedures to assist in safely retracting and then
lowering the boom. Read this information from start to fin-
ish before performing any of these procedures to fully un-
derstand the process and the danger involved. If unsure
about any part of these procedures, contact the nearest
JLG Authorized Service Center (ASC) or the JLG Ser-
vice Department for specific instructions.
4.38
DO NOT get under a
Every attempt should be made to repair a hydraulic line
failure, and to retract and then lower the boom in its nor-
mal fashion. However, this is not always possible. Step-
by-step procedures are listed here (STEP 3 and STEP 4)
for when the boom must be retracted and lowered imme-
diately and replacement hydraulic lines or other parts are
not available. Only resort to these procedures (STEP 3
and STEP 4) only when absolutely necessary.
IMPORTANT: The boom must first be retracted, and
then lowered, to avoid vehicle tipover.
Whenever there is hydraulic line failure, it is critical to
correctly identify which hydraulic line has failed. Identify
the hydraulic line that has failed and use the following ta-
ble to help determine which step to follow to retract and
lower the boom.
Boom troubleshooting steps to follow for hydraulic line
failure and for EMERGENCY OPERATIONS.
HYDRAULIC
THIS STEP
LINE
IF PARTS
THAT
FAILED
AVAILABLE
BOOM LIFT LINE
3 (LIFT CYLINDER
TO BULKHEAD)
BOOM LIFT LINE
4 (BULKHEAD TO
CONTROL VALVE)
BOOM LOWER
LINE
5
(LIFT CYLINDER
TO BULKHEAD)
BOOM LOWER
LINE
6
(BULKHEAD TO
CONTROL VALVE)
BOOM EXTEND
1
LINE
BOOM RETRACT
2
LINE
EMERGENCY
NORMAL STEPS
FOLLOW
FOLLOW
THIS
STEP
FOLLOW
IF PARTS
ARE
ARE NOT
STEP AS A
AVAILABLE
RESORT
STEP 1 STEP 2
STEP 1 STEP 2
STEP 1
STEP 1
STEP 1 STEP 2
STEP 1
Model MMV Rev. 12/04
STEPS
THIS
LAST
STEP 3
STEP 3
STEP 4