TM 9-4940-568-34
2-66
Table 2-7. Crane Troubleshooting (CONT).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
10. BOOM DOES NOT RAISE OR LOWER (Continued).
Test 2.
Remove five function control cover. Refer to paragraph 3-31. Disconnect the line that
comes from the boom cylinder lower fitting on the boom control valve. Install a flow meter in
line between control valve and line. Open pressure control valve fully by turning control
knob counter clockwise to DECREASE. Start FRS. Have assistant operate BOOM control
lever to attempt to lower boom. Slowly close pressure control valve by turning knob
clockwise to INCREASE. Create 3,000 - 3,200 psi (20,684 to 22,063 kPa) working
pressure.
If pressure is within specifications, repair or replace boom lift cylinder. Refer to
paragraph 3-18 or 6-9.
If pressure is not within specifications, repair boom control valve/shuttle valve
circuit. Refer to paragraph 3-35. If fault is not corrected, repair or replace boom lift
cylinder. Refer to paragraph 3-18 or 6-9.
END OF TEST
BOOM
BOOM
CONTROL
LEVER
LOWER
