TM 9-2350-256-34-2
Table 2-3. Troubleshooting--Continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
HOISTING BOOM CIRCUIT (MAIN HYDRAULIC SYSTEM) - Continued
WARNING
Main winch must be in high range. (Step 12 only).
Step 12.
Test for faulty pilot operated relief and unloading valve. Attempt operation of spade and winches. If winches operate, but spade and
boom fail to operate, it indicates a faulty pilot operated relief and unloading valve. Shift main winch into high range an inhale cable
completely (clevis contacting front of plate). Continue holding main winch control lever in this position and attempt to operate boom
combination control valve lever. Release both levers to neutral and operate boom combination control valve lever. If boom does not
function, replace pilot operated relief and unloading valve. Refer to TM 9-2350-256-34-1, Medium Recovery Vehicle, M88A1.
Step 13.
Test for boom combination control valve failure. Install pressure gage in pilot operated relief and unloading valve
gage port. If, when actuating spade combination control valve lever, operating pressure (1950-2050 psi) is recorded on pressure gage,
but when actuating boom combination control valve lever, no pressure is recorded on gage, it indicates a faulty boom combination control
valve. For location of valve gage port, refer to view B. fig. 3-22. Replace boom combination control valve. Refer to TM 9-2350-256-34-1,
Medium Recovery Vehicle, M88A1.
Step 14.
Test for restricted hydraulic hose or flow regulator. Install pressure gage in pilot operated relief and unloading valve
gage port. If, when actuating boom combination control valve lever, operating pressure (1950-2050 psi) is recorded on pressure gage, it
indicates valve is functioning properly. Inspect for restricted hydraulic hose or obstruction in flow regulator. For location of valve gage
port, refer to view B, fig. 3-22.
a. Replace any restricted hydraulic hose. Refer to TM 9-2350-256-20, Medium Recovery Vehicle, M88A1.
b. Remove any obstruction or replace flow regulator. Refer to TM 9-2350-256-34-1, Medium Recovery Vehicle,
M88A1.
Step 15.
Inspect for mechanical failure of boom or hydraulic cylinder attaching pins.
Replace any damaged pins. Refer to TM 9-2350-256-34-1, Medium Recovery Vehicle, M88A1.
25. BOOM OPERATES PARTIALLY
Step 1.
Test for improperly adjusted pilot operated relief and unloading valve. Install test gage in valve gage port. With
engine operating at 1800 rpm, and spade in stowed position, place spade combination control valve lever in RAISE
position and adjust relief valve.
Adjust relief pressure to 1950-2050 psi. For location of valve gage port, and adjusting screw, refer to views B and C, fig. 3-22.
Step 2.
Inspect for mechanical binding of boom and cylinder mounting pins. Replace any broken or damaged pins. Refer to TM 9-2350-256-34-
1, Medium Recovery Vehicle, M88A1.
26. BOOM WILL NOT HOLD IN ANY POSITION
Step 1.
Inspect hydraulic hoses and connections for oil leaks
.
Repair leaks or replace hydraulic hose. Refer to TM 9-2350-256-20, Medium Recovery Vehicle, M88A1.
Step 2.
Test for boom combination control valve failure. Install pressure gage in pilot operated relief and unloading valve
gage port. If when actuating spade combination control valve lever, no pressure is recorded on gage, it indicates a
faulty boom combination control valve. For location of valve gage port, refer to view B, fig. 3-22.
Replace boom combination control valve. Refer to TM 9-2350-256-34-1, Medium Recovery Vehicle, M88A1.
27. BOOM WILL NOT STOP AUTOMATICALLY AFTER LIVE BOOM OPERATION
Step 1.
Inspect boom limit valve for defective or broken actuating arm linkage.
Repair or replace actuating arm linkage. Refer to TM 9-2350-256-20, Medium Replace Vehicle, M88A1.
Step 2.
Inspect boom limit valves for proper adjustment.
Adjust boom limit valves. Refer to TM 9-2350-256-20, Medium Recovery Vehicle, M88A1.
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