TM 9-4940-568-34
2-64
Table 2-7. Crane Troubleshooting (CONT).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
10. BOOM DOES NOT RAISE OR LOWER.
WARNING
Never disconnect any hydraulic hose or part while FRS is run-
ning. Allow several minutes for pressure to relieve itself. With
FRS, operate control valves fully in each direction to relieve
trapped pressure.
Before testing hydraulic system with a flow meter, always open
the pressure control valve all the way by turning the knob
counter clockwise to DECREASE. Failure to do so may cause
hydraulic lines to burst, causing personal injury.
When increasing hydraulic system pressure with the pressure
control valve, always increase pressure slowly. If pressure is in-
creased too fast, damage to hydraulic system or test set will re-
sult.
CAUTION
Checking system pressure involves putting valves into relief. Relief is defined as a
point when a needed system pressure is reached, causing excessive pressurized
hydraulic fluid to be directed to the hydraulic reservoir.
Relief is accomplished either by operating the system in a manner which will create
relief or by using the loading valve on the flow meter, which will simulate the
operating conditions. Putting valves into relief should be limited to no more than 10
seconds to prevent excessive heat buildup.
NOTE
Unless called for in the test being done, all pressure tests will be done with FRS 24
V MASTER switch in the ON position, and hydraulic oil temperature at 130-150 F
(54-66 C).
Unless advised otherwise, the FRS 24V MASTER switch and the crane MAIN
POWER switch must be in the ON position for all voltage checks.
Before performing troubleshooting procedures, make sure there are no restrictions
in pressure or return lines.
If a boom lift cylinder must be isolated, connect flow meter at cylinder and discon-
nect line between cylinders.
If boom does not lower, go to Test 2.
