TM 10-3930-669-20 WARNING • High-pressure    hydraulics    [oil    under    3,000    psi    (20,700    kPa)    pressure]    operate    this equipment.  Refer to vehicle operator and maintenance manuals for hydraulic oil pressure. Never  disconnect  any  hydraulic  line  or  fitting  without  first  dropping  pressure  to  zero. Failure to comply may result in injury to personnel. • Hydraulic oil is slippery and can cause falls.  To avoid injury, wipe up spilled oil with rags. PRESSURE TEST (1) Remove test port plug and connect a 0 to 4,000 psi (0-27,567 kPa) pressure gauge to PRIMARY PUMP PRESSURE test port. (2) Start engine (TM 10-3930-669-10). (3) With aid of an assistant, move tilt/lift joystick to raise position and observe pressure gauge (TM 10-3930-669-10). (a) If 2,000 to 2,600 psi (13,780- 17,920 kPa) are not measured, hydraulic pump is faulty. Perform Steps (4) and (5) below and notify DS Maintenance. (b) If 2,000 to 2,600 psi (13,780- 17,920 kPa) are measured, stack valve is faulty.  Notify DS Maintenance. (4) Shut down engine. (5) Remove pressure gauge from PRIMARY PUMP PRESSURE test port and install test port plug. (6) Close right-hand engine access cover VERIFY REPAIR (1) Start engine (TM 10-3930-669-10). (2) Operate  mast  lift  cylinders  and  observe lift speed. (a) If mast lift speed is sluggish, fault not  corrected.    Perform  Step  (3) below.        Repeat    procedure    and notify Supervisor. (b) If  mast  lift  speed  is  normal,  fault corrected. (3) Shut down engine. 2-487