ADJUSTMENT OF BOOM HOIST RELIEF VALVE

TM 10-3930-660-24-1

MAIN CONTROL VALVE MAINTENANCE - CONTINUED

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ADJUSTMENT OF BOOM HOIST RELIEF VALVE

NOTE

The main relief valve pressure must be adjusted above normal operating pressure to permit the boom hoist

relief valve pressure to be adjusted. Main relief valve pressure is then returned to normal operating pressure

at the end of this procedure.

Remove main relief valve plug (11).

Connect 0 to 5,000 psi (0 to 34474 kPa) pressure gauge to plug port (12).

Remove acorn nut (13) covering slotted head adjusting screw (14).

While holding adjusting screw (14), loosen and back off jamnut (15) which secures adjusting screw.

NOTE

Engine may be operated at idle or full throttle when performing pressure tests.

Start engine (TM 10-3930-660-10).

Operate boom extend, retract, hoist or lower function

until hydraulic oil is passing over relief valve. Con-

tinue to hold hydraulic lever in that position so oil

passes over relief valve during relief valve adjustment.

Turn adjusting screw (14) clockwise (in) until pressure

on gauge reads 3,100 psi (21374 kPa).

Release hydraulic function lever.

Remove acorn nut (19) covering slotted head adjust-

ing screw (20).

10.

While holding adjusting screw (20), loosen and back

13,14

off jamnut (21) which secures adjusting screw.

11.

Operate boom hoist function until boom is fully

raised. Continue to hold boom control lever in position

so hydraulic oil passes over relief valve. Read relief

19,20

valve pressure on pressure gauge.

12.

Adjust boom hoist relief valve pressure between 2,950

409-659

to 3,050 psi (20340 to 21029 kPa).

13.

To increase relief pressure, turn adjusting screw (18) clockwise (in). To decrease pressure, turn adjusting screw counter-

clockwise (out).

14.

Hold adjusting screw (20) in position and tighten jamnut (21). Install acorn nut (19).

Perform steps 4 through 13 of Adjustment of Main Relief Valve.

15.

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