TM   55-2840-241-23 CHAPTER  4 TROUBLESHOOTING 4-1.  General. a. The  troubleshooting  procedures  in  this  chapter are presented as a guide for locating and correcting malfunctions.   Use of  these  procedures  will  reduce delays  and  maintenance  down  time  and  will  minimize unnecessary  replacement  of  engine  components.  Two basic  assumptions  have  been  made  in  preparing  these procedures;  (1)  the  correct  operating  procedures  have been  followed  and  (2)  the  problem  is  caused  by  a  single failure  or  malfunction. b. The  troubleshooting  procedures  are  organized under three basic heading; (1) Trouble, (2) Probable cause,  and  (3)  Remedy. c. The trouble as reported by the flight crew is the main point of the problem. Obtain as much informa- tion  as  possible  from  the  flight  crew  and  their  report.  In many cases, this information will define the problem completely,  however,  the  malfunction  should  be  con- firmed by a ground run, providing there is no danger of possible  engine  damage  occurring. d. The probable cause lists the components which might cause the malfunction. The cockpit indications can often give a clue as to which of these components is causing  the  problem. e. Caution  must  be  exercised  to  avoid  troubleshoot- ing  difficulties  caused  by  false  cockpit  indications.  In most cases, a false indication can be detected by check- ing it against other indications. For example, a TOT indication system malfunction should be suspected if TOT is high, low, or fluctuating with no change in fuel flow or torque. f. The remedy lists the action to be taken to correct the   malfunction. g. It  is  not  possible  to  list  troubleshooting  pro- cedures  for  every  malfunction  which  can  occur  There will be situations encountered for which there are no applicable procedure but the methods and principles used in the procedures are effective in all maintenance problems. Table 4-1. Troubleshooting Item Trouble Probable  cause Remedy 1   Engine   fails   to   reach light   off   cranking speed. 2   Engine   fails   to   light off — fuel vapor coming  out  of  exhaust and  no  audible ignition     operation. a.   Inadequate   starter torque  caused  by  low battery   or   defective starter-generator. b.  B  and  C  leads  on starter-generator terminal    block    reversed. c.   N₁ binding. a.   Preservative   oil fouling   spark   igniter. b.   Faulty   circuit   to ignition    exciter. a(1).   Check   battery. a(2).  Check  for  loose  cables. a(3).   Check   starter-generator   and replace  if  defective.  (Refer  to  TM 55-1520-228-23.) b.  Reverse  B  and  C  leads. C(1).  Check  inlet  for  foreign  object damage.   Rotate   N1 by   hand   and listen   for   abnormal   noise. c(2).  Replace  engine.  (Refer  to  TM 55-1520-228-23.) a.   Try   a   second   start. b.  Check  input  power  to  exciter.  If no  power,  isolate  defective component   and   correct   fault. Change   14   4-1