TM 10-3930-671-24 INJECTORS When    replacing    injectors    in    the    cylinder    head    it    is essential that a new heat shield washer be fitted between the nozzle cap and the cylinder head (Reference Section 8, Heat Shield & Injector). Tighten injectors evenly to 50-55 Ib-ft (70 N.m).  Injectors should  be  taken  out  only  if  engine  is  malfunctioning  as outlined below: 1. Misfiring. 2. Knocking in one (or more) cylinder(s). 3. Engine overheating. 4. Loss of power. 5. Smoky exhaust (black or white). 6. Increased fuel consumption. 7. To perform a compression test. The    faulty    injector    or    injectors    may    be    located    by loosening  the  line  fitting  nut  on  each,  in  turn,  with  the engine  running  at  a  fast  idle.    This  allows  the  fuel  to escape  and  not  enter  the  cylinder.    The  injector  least affecting   the   engine   performance   should   be   removed from the cylinder head and reconditioned or replaced. No attempt should be made to adjust the Injection pressure without a proper   testing   pump   and   pressure gauge.    It  is  Impossible  to  adjust  the setting of the Injector with any degree of accuracy without proper equipment. TESTING Injectors   should   not   be   disassembled   unless   testing shows  that  cleaning  or  other  service  is  needed.    Any disassembly  of  the  fuel  injectors  should  be  done  in  an extremely clean work area.  The exterior of the injectors should  be  rinsed  with  cleaning  solution  before  testing. Be careful not to flush any debris into  the  open  ports  of the injector. Before   testing   each   injector,   turn   it   upside   down   and shake  it.    This  may  get  rid  of  any  debris  that  has  just entered   the   nozzle   during   the   removal   and   cleaning process. Use  a  special  hydraulic  injector  tester  equipped  with  a filter so that only clean oil enters the injector.  There are many   testers   on   the   market-follow   the   manufacturer’s instructions  for   correct   and   safe   operation   of   the   test equipment chosen. Bodily  injury  may  result  during  this operation   if   care   is   not   exercised. The     high     velocity     of     spray     may puncture   the   skin   and   cause   blood poisoning.        Keep    hands    and    face away from the nozzle spray. Before testing, determine the brand name of the fuel  injector  about  to  be  tested.    TMD  engines currently   use   injectors   made   by   two   different companies.    One  company  is  CAV,  the  other  is STANADYNE.    They  look  very  much  alike,  but are   never   mixed   together   on   any   one   engine because   of   different   operating   pressures.   The nozzles  are  identified  by  very  small  lettering  on the outside of the nozzle as follows: STANADYNE - stamped just under the bleed-off tubes. After having identified the nozzle, connect it to the tester. STEP 1: Set  tester  so  that  it  will  apply  pressure  and then   work   the   pump   handle   several   sharp strokes.    This  will  dislodge  some  light  carbon buildup   from   the   tip   of   the   nozzle   and   may remove any very fine dirt particles in the nozzle cavities. STEP 2: Now     work     the     pump     handle     slowly     and observe  the  opening  pressure.    Compare  to the following chart. STANADYNE Acceptable Pressure Limits *New Injector = 2150 - 2250 PSI (148.2- 155.1 BAR) **Service Injector = 1925 - 2250 PSI (132.7- 155.1 BAR) * A new injector is an injector with no engine "run time" on it. ** A  service  injector  is  considered  to  be  any  injector that  has  been  in  use  or  any  injector  that  has  been reconditioned and no new parts were involved.  The lower acceptable limit figures for the service injectors are necessary due to nozzle needle embedment and spring relaxation that takes place after a nozzle has been put into use. F-153