Section  VII.  NOZZLE  HOLDER  ASSEMBLIES 14-37.   General. a.  Each  engine  cylinder  is  provided  with  a  multi- hole,   differential   needle,   hydraulically   lifted,   nozzle holder  assembly. The  function  of  each  nozzle  holder assembly  is  to  direct  a  metered  quantity  of  fuel  re- ceived  from  the  fuel  injection  pump  into  the  corres- ponding  engine  combustion  chamber  in  a  highly  atom- ized,   pre-determined   spray   pattern   in   such   reamer as   to   produce   the   most   efficient   performance.   Each nozzle   holder   assembly   consists   of   two   assemblies, an  injection  nozzle  holder  and   an  injection  nozzle. b.  The  holder  assembly  positions  the  nozzle  in  the cylinder  head  and  provides  a  means  of  conducting fuel  received  from  the  fuel  injection  pump  to  the nozzle.   The   holder   consists   of  a  steel  holder   body, two  locating  dowels,  spindle,  spindle  spring,  pres- sure  adjusting  screw,  adjusting  screw  locknut,  gas- kets,  cap  nut,  and  a  nozzle  retaining  nut. c.  The  nozzle  assembly  consists  of  a  nozzle  valve and–a  nozzle  body  in  which  are  located  four  spray orifices  equally  spaced  90  degrees  apart.  The nozzle   valve   is   operated   hydraulically   within   the valve  body  by  fuel  delivered  under  pressure  by  the fuel  injection  pump. The  nozzle  is  positioned  on  the holder  by  two  dowels  whereby  the  four  spray  orifices are  fixed  on  a  plane  parallel  to  the  piston  top,  and the  nozzle  fuel  duct  is  registered  with  the  holder  fuel duct . d.   Fuel   enters   the   nozzle   holder   fuel   inlet   passage, passes  through  the  holder  fuel  duct  into  the  nozzle fuel  duct  via  an  annular  groove  in  the  nozzle  body, and  then  into  the  pressure  chamber  above  the  nozzle valve   seat. At  the  instant  the  fuel  pressure  in  the pressure   chamber   exceeds   pressure   exerted   on spindle  and  nozzle  valve   by  the   spindle   spring,   the nozzle  valve  is  lifted  off  its  seat  (popped)  and  fuel  is forced  through  orifices  in  the  valve  body  end  and  into the  corresponding  engine  combustion  chamber.  The nozzle   valve   is   returned   to   its   seat   by   pressure   exer- ted  by  the  spindle  spring  when  the  fuel  injection  pump has  ceased  to  deliver  fuel  to  the  nozzle  holder. 14-38,    Removal. Refer   to   the   Operator Manual  to  remove  the 14-39.   Disassembly, and   Organizational   Maintenance nozzle   holder   assembly. Cleaning   and   Repair. NOTE When  more  than  one  nozzle  holder assembly   is   disassembled,   keep parts   of   each   separate.   Complete disassembly   of   the   nozzle   holder assembly   is   seldom   necessary.   In most   cases,   only   disassembly   and cleaning  of  the  nozzle  valve  body  and valve  is  required  to  place  the  nozzle holder  in  good  operational  condition. At   completion   of   repair,   check   operation   in   accord- ance   with   paragraph   14-40. The  nozzle  valve  and  nozzle  valve  body  are  mated parts,  and  must  be  kept  together.  If  replacement  of either  part  is  necessary,  both  parts  must  be  re- placed   as   matched   sets.   Remove,   clean,   and   in- spect  the  nozzle  valve  body  and  valve  as  follows: a.  Clamp  nozzle  holder  body  in  a  suitable  holding fixture. b. Remove  cap  nut  (10)  and  gasket  (11)  from  upper end   of   nozzle   holder   (15).   Loosen   pressure   adjusting screw   locknut   (8)   and   turn   pressure   adjusting   screw (9)  out  sufficiently  to  release  spring  tension  on  spindle spring   (12).   See   figure   14-19. c. Using  a  suitable  socket  or  box  wrench,  loosen and   remove   the   nozzle   retaining   nut   (5).   Remove the  nozzle  valve  body  (3)  and  nozzle  valve  (4)  from the   retaining   nut. Start  the  nut  back  onto  the  holder body  to  protect  the  lapped  end  of  the  holder  body (15). d. plate CAUTION Do  not  allow  the  solution  to  get  on the  hands  or  body;  use  tweezers  or  the basket  method  to  handle  the  parts. Withdraw  the  valve  from  the  valve  body  and it  in  a  carbon  and  rust  remover  solution  for cleaning.   Normally,   the   valve   can   easily   be   with- drawn  from  the  valve  body,  however,  in  some  cases it  may  be  necessary  to  soak  the  valve  body  and  valve in  carbon  removing  compound  Type  2  per  Federal Specifications   P-C-111   before   the   valve   can   be   with- drawn.   For   faster   and   better   cleaning   results,   the carbon  removing  compound  should  be  heated  to approximately   200°   F. The   parts   generally   can   be separated   in   two   or   three   minutes;   however,   if necessary  they  can  be  left  in  the  solution  longer. After   removing   the   parts   from   the   solution,   immedi- ately   place   them   in   clean   diesel   fuel   for   neutralizing. Always  handle  the  parts  carefully  to  protect  the lapped   surfaces. The  valve  (4)  and  the  seat  in  the  valve  body (3)  are  originally   ground   to   slightly   different angles  to  provide  a  line  contact  seat  between  the two   parts. Practically   all   the   wear   occurs   in   the seat  in  the  valve  body. The  valve  should  never  be lapped  to  the  seat  in  the  valve  body. f. Using  a magnifying   glass,   inspect   condition of  seat  in  the  valve  body  (3).  If  the  seat  is  damaged or  worn  in  any  way  to  prevent  proper  seating  of  the valve,   the   nozzle   assembly   (1)   must   be   replaced. g.  The  outer  surfaces  of  the  valve  body  (15)  may be  cleaned  with  a  brass  wire  brush.  Do  not  scrape carbon  from  the  surface  around  the  orifices  in  tip  of valve  body  with  any  hard  object  as  damage  may  re- sult.  Clean  the  four  orifices  in  the  valve  body  tip Change  1  14-27