TM10-3930-660-20 18-6. MAIN CONTROL VALVE ASSEMBLY - ADJUST/REPLACE (Cont‘d) a. Unscrew main relief valve plug assembly  (1). b. Connect O to 5000 psi pressure gauge to plug assembly port (2). c. Remove acorn nut (3) covering slotted head adjusting screw. d. While holding adjusting screw, loosen and back off jam nut (4) which secures adjusting screw. 2. ADJUST MAIN RELIEF VALVE PRESSURE TO 3,100 psi. Engine may be operated at idle or full throttle when performing pressure tests. a. Start engine, TM10-3930-660-10. b. Operate boom extend, retract, hoist or lower function until hydraulic oil is passing over relief valve. Continue to hold hydraulic lever in that position so oil passes over relief valve during relief valve adjustment. c. Turn adjusting screw clockwise (in) until pressure on gauge  reads 3,100 psi. d. Release hydraulic function lever. 3. ADJUST BOOM EXTEND RELIEF VALVE PRESSURE BETWEEN 2,950 AND 3,050 psi. a. Remove acorn nut (5) covering slotted head adjusting screw. b. While holding adjusting screw, loosen and back off jam nut (6) which secures adjusting screw. 18-22