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) Tag  and  disconnect  lift  cylinder  hose  at stack valve lift spool port A hose fitting. (2) Connect  a  0  to  4,000  psi  (0-27,567  kPa) pressure  gauge  to  stack  valve  lift  spool port A hose fitting. (3) Install   pressure   plug   in   stack   valve   lift spool port A hose. (4) Start engine (TM 10-3930-669-10). (5) With   aid   of   an   assistant   operate   any hydraulic   control   and   observe   pressure gauge. (a) If 2,000 to 2,600 psi (13,780-17,920 kPa) are not measured, stack valve is faulty.  Perform Steps (6) and (7) below and notify DS Maintenance. (b) If 2,000 to 2,600 psi (13,780-17,920 kPa) are measured, mast adjustment is faulty.  Perform Steps (6) through (8) below and notify DS Maintenance. (6) Shut down engine. (7) Remove   pressure   gauge,   tag,   and   plug and connect hose to stack valve lift spool port A fitting. (8) Install cab (Para 15-2). VERIFY REPAIR (1) Start engine (TM 10-3930-669-10). (2) Operate  mast  lift  cylinders  to  maximum height with load. (a) If   lift   cylinders   do   not   lift   load   to maximum height, fault not corrected.  Perform Step (3) below. Repeat procedure and notify Supervisor. (b) If  lift  cylinders  lift  load  to  maximum height, fault corrected. (3) Shut down engine. 2-473