TM5-6115-584-12 NAVFAC   P-8-622-12 TO-35C2-3-456-1 TM-05682C-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   tnjection   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 t o 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 outside of fuel tank. Remove tank from skid-base. On ASK equipped generators, remove top panel, left side panel and side closure (Refer to paragraphs 5-4, 5-5, and 5-12). c.  Disassembly. (1)  Fuel  Level  Gauge.  Unscrew  and  remove  fuel level  gauge  (5)  using  tools  only  on  the  hex  portion  of the gauge. (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  7 (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 Gauge. Check that fuel level gauge 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. 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 MIL-S-22473.   Tighten   valve   assembly   into   adapter (11). (2)  Fittings.  Engage  threads  of  fitting  (7)  l/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  MIL-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.