TM 9-4940-342-14&P parts are reassembled in the exact former position. 6-3. Motor Assembly (Refer to Fig C-10) a.  The motor should be inspected and defective components replaced. b.  To repair the motor proceed as follows: (1)  Remove    pulley    setscrew(s)    and    slide pulley clear from motor shaft. (2)  Remove  motor  electrical  box  cover,  tag electrical    wires    for    proper    reinstallation    and proceed to remove electrical wire nuts. (3)  Remove   electrical   cable   connector   nut located inside of motor of motor junction box. (4)  Inspect  motor  components  and  replace  as required. 6-4. Fuel Pump Repair (Refer to Fig C-12) a.  The  fuel  pump  is  designed  to  give  years  of trouble-free   service   with   minimum   maintenance, providing that only clean filtered kerosine, fuel oils or  diesel  are  used  and  fuel  is  kept  free  of  water. Never  attempt  to  use  gasoline  or  solvents  of  any type   or   fuels   containing   gasoline,   drain   oils   or solvents. Avoid operating fuel pump without fuel in supply tank. b.  Fuel   pump   is   equipped   with   a   two-pipe system, fuel supply line and fuel return line, which provides   self-priming   and   air   purging   oil   fuel system. Keep both lines open, clean and free of any leaks. (1)  The fuel pump is factory set to operate at 100-125  psi  on  fuel  pressure  service  gage.  Any appreciable collapse of pressure indicates excessive by-pass at by-pass plug, missing or damaged valve gasket, worn piston assembly seal or worn gear set. (2)  The    fuel    pump    has    a    cut-off    valve designed  to  stop  all  oil  flow  to  fuel  nozzles  when pump   pressure   drops   below   approximately   85 pounds. This prevents fuel dribble at nozzle during shutdown or startup. If unit smokes during fire ON or OFF operation, cutoff valve could be leaking. To check,  temporarily  remove  fuel  pressure  gage  and plug  pressure  gage  port.  Remove  tube  fittings  to burner  nozzle  and  install  fuel  pressure  gage  in  its place.  Operate  fuel  pump  in  ON  position  at  pump motor   switch,   then   shut   switch   OFF.   The   gage should   hold   approximately   85   psi   or   more.   If pressure  drops  below  the  cut-off  point  the  valve assembly    should    be    disassembled,    cleaned    or replaced, if necessary. c.   If    seal    leakage    is    suspected,    the    seal assembly  may  be  disassembled  by  removing  the three  10-24  screws  from  retainer  ring,  lifting  off retainer, seal spring and removing seal diaphragm.  If  required,  the  drive  shaft,  gear  set and thrustwasher can be removed for inspection or replacement. d.  Before   reassembly,   dry   the   seal   chamber above the shoulder in the pump body. To make sure there  is  some  end  play  in  shaft  after  reassembly, pull on the shaft. Also make sure that the tab on the thrustwasher  mates  with  either  seal  drain  hole  in pump body prior to reassembly of seal. e.  The  fuel  pump  is  equipped  with  an  internal filter  and  it  should  not  be  necessary  to  clean  or service  it  until  five  or  six  months  after  unit  is  in service.  This  is  due  to  the  effective  self-cleaning action of the rotary filter. f.   To inspect or clean filter, remove filter cover by  removing  the  six  10-24  screws.  Carefully  pry cover off, taking care not to damage the front cover gasket. Wipe inside of cover clean, if necessary and replace. 6-5. Flame    Safeguard,    Scanner    and    Relay Maintenance (Refer to Para 4-26) a.  With   all   external   limit   switches   to   flame safeguard relay satisfied, terminals of the relay will be powered in the following sequences. (1)  Terminal   no.   7   of   the   flame   safeguard control   will   be   powered   through   limit   control circuit no. 3. (2). Flame safeguard terminal no. 8 is powered through LS-1 (lockout switch). If LS-1 is open, the flame safeguard requires a manual reset. (3)  Terminal  no.  8,  in  turn,  powers  terminal no. 6 and flame safeguard transformer T1. (4)  With  T1  transformer  powered,  the  time delay  network  is  energized  through  the  LS  heater and    contact    RF-2    initiating    the    seven-second prepurge timing. (5)  After    completion    of    the    seven-second purge,  the  TD  (time  delay)  relay  is  energized  and contact TD-1 closes, locking in the TD relay. (6)  Contact    TD-2    also    closes,    energizing terminal  no.  3  and  terminal  no.  4  through  contact RF-3. Contact TD-3 opens. (7)  Terminal  no.  3  powers  circuit  no.  7  to open  the  low  fire  fuel  valve.  At  the  same  time, terminal  no.  4  powers  circuit  no.  4  to  power  the ignition  transformer,  producing  the  spark  to  ignite the fuel. (8)  When  the  fire  has  been  established  and detected by the UV flame detector, a signal will be transmitted  to  the  flame  detector  network  through terminals S1 and S2. (9)  The flame signal is amplified in the flame detection    network    and    flame    relay    (RF)    is energized. 47