TM5-6115-585-12 NAVFAC    P-8-623-12 TO-35C2-3-455-1 TM-05684C/05685B-12 Section  IX.  MAINTENANCE  OF  FUEL  SYSTEM 4-18.  DESCRIPTION  AND  FUNCTION. a.   Low   Pressure   System   (see   Schematic   figure 1-5). (1)   Fuel   pump   may   draw   fuel   from   an   external source   to   fill   set   tank   or   set   tank   may   be   filled   man- ually.   If   an   external   fuel   source   is   selected,   a   float valve   assembly   in   the   set   tank   maintains   the   fuel level   in   the   tank.   Two   other   fuel   pumps   (in   series) draw  fuel  from  the  set  tank  and  force  the  fuel  through a   primary   strainer,   two   filters,   and   a   check   valve assembly,   to   the   injection   pump. b.  High  Pressure  System. (1)   Fuel   injection   pump   forces   the   fuel,   under high   pressure,   to   the   fuel   injection   nozzles.   The   in- jection   nozzles   provide   fuel   to   each   combustion chamber   of   the   engine.   Unused   fuel   is   returned   from the   injectors   to   the   fuel   tank.   A   cam   and   gear   on   the camshaft   drives   the   fuel   injection   pump.   The   gear drives  the  pump  face  gear,  providing  fuel  distribution to   each   cylinder   in   the   proper   order.   The   cam   oper- ates   the   pump   plunger,   pressurizing   fuel   to   the   noz- zles.   A   control   sleeve   meters   fuel   by   controlling   the length  of  time  the  plunger  spill  port  is  closed,  main- taining  pressure,  and  therefore,  the  amount  of  fuel delivered   in   each   stroke.   The   pintle   type   injection nozzles   are   conventional   inward   opening   with   ad- justable   opening   pressure.   They   are   factory   adjusted to  open  at  1900  to  1950  psi. 4-19.   FUEL   TANK   ASSEMBLY_< a.   Inspection   on   Equipment.   Refer   to   paragraph 3-13a. b. Removal (see figure 4-7). Drain fuel into suitable container by opening drain valve. Tag and disconnect fuel hoses from fuel tank fittings. Disconnect electrical lead from electrical connector (10). Remove nut (1) and flatwasher (2) from straps (3) on out- side of fuel tank. Remove tank from skid-base. On ASK equipped generators, remove top panel, left panel and side closure assem- blies   (para.   5-4   and   5-5). c.  Disassembly. (1)  Fuel  Level  Gage.  Unscrew  and  remove  fuel level   gage   (5)   using   tools   only   on   the   hex   portion   of the  gage. (2)   Float   Switch.   Unscrew   collar   and   disconnect electrical   connector   (10)   if   not   previously   discon- nected.   Unscrew   and   remove   float   switch   (6)   using tools   only   on   the   square   portions   of   the   switch. (3)  Unscrew  and  remove  fittings  (7). (4)   Holding   pipe   adapter   (11)   with   a   wrench,   un- screw  and  remove  drain  valve  (8). 4-16 Change 8 (5)   Loosen   filler   cap   and   remove   filler   cap   (4)   and strainer   (5). d.  Cleaning  and  Inspection. (1)  Tank.  Clean  tank  exterior  using  suitable  sol- vent   and   clean   cloth   and   brush.   Inspect   tank   for signs  of  physical  damage.  If  damaged  refer  to  higher level   of   maintenance. (2)   Fuel   Level   Gage.   Check   that   fuel   level   gage face   is   clean   and   readable.   Check   that   as   cork   float is   moved   up   and   down,   the   meter   movement   rotates. (3)   Float   Switch.   Inspect   terminal   connector   for damage  to  threads.  Check  to  see  that  float  slides  on shaft   without   binding.   Clean   with   suitable   solvent   if required. (4)   Fittings.   Inspect   fittings   for   good   leak-free seating  on  tank  and  check  threads  for  physical  damage. (5)  Fuel  Drain  Valve  Assembly.  Check  that  drain valve  does  not  leak  and  threads  for  physical  damage. (6)  Strainer.  Invert  and  clean  with  solvent. e.  Test. (1)  Float  Switch.  Remove  float  switch  (6)  from tank   (9).   Using   an   ohmmeter,   check   for   continuity between   terminals   A   and   B   of   switch   (see   figure 4-8).   Switch   should   show   no   continuity   when   float   is up.   Switch   should   close   when   float   drops   to   2-7/8 ±3/16   inch   from   threaded   collar   of   float   switch.   Re- place   switch   if   it   does   not   operate   properly. (2)   Tank.   If   tank   shows   signs   of   physical   dam- age  or  leaks  refer  to  higher  level  of  maintenance. f.  Reassembly  (see  figure  4-7). (1)   Fuel   Drain,   Valve.   Engage   threads   of   fuel drain   valve   assembly   (8)   1/2   turn   into   fuel   tank adapter   (11).   Coat   threads   with   sealing   compound ML-S-22473.   Tighten   valve   assembly   Into   adapter (11). (2)   Fittings.   Engage   threads   of   fitting   (7)   1/2   turn into   fuel   tank   (9).   Coat   threads   with   sealing   com- pound   MIL-S-22473.   Tighten   fittings   into   tank.   Fit- tings  should  face  Generator  Set  for  proper  connection of   fuel   lines.   Attach   fuel   lines   to   fittings. (3)   Float   Switch.   Engage   threads   of   float   switch (6)   1/2   turn   into   tank   (9).   Coat   threads   with   sealing compound   ML-S   22473.   Tighten   float   switch   (6)   into tank   using   tools   only   on   square   portion   of   switch.   At- tach   electrical   lead   to   connector   (10)   on   top   of   float switch   and   tighten.