TM10-3930-660-20 18-6. MAIN CONTROL VALVE ASSEMBLY - ADJUST/REPLACE (Cont‘d) 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 HOIST RELIEF VALVE PRESSURE BETWEEN 2,950 AND 3,050 psi. a. Remove acorn nut (7) covering slotted head adjusting screw. b. While holding adjusting screw, loosen and back off jam nut (8) which secures adjusting screw. c. Operate boom hoist function until boom is fully raised. Continue to hold boom control lever in position so hydraulic oil passes over relief valve. d. Read relief valve pressure on Pressure gauge. e. To increase relief pressure, turn adjusting screw clockwise (in). To decrease pressure, turn adjusting  screw  counterclockwise (out) . f. When desired relief pressure is obtained, release boom hoist lever. g. Hold adjusting screw in position and tighten jam nut (8). Install acorn nut (7). 18-25