TM 55-2840-241-23 Table   4-1.   Troubleshooting   (Continued) Item Trouble Probable   cause Remedy 8   Engine   speed   cycles a.   Gas   producer   fuel control  bypass  valve  not operating    freely. b.  Check   rigging 9   Engine   unstable above  idle  speed. 10   Idle   speed   too   low. a. Leak(s)   in   fuel   system air   tubes. b.  Double  check  valve. c.   Contamination   in   the pneumatic  section  of  the gas  producer  fuel  control and   power   turbine governor. d.   Defective   fuel   control or  governor. e.   Accumulator(s) leaking, f.   Contaminated   fuel control/fuel   filter. 8. Incorrect   gas   producer lever   setting. b.    Malfunctioning tachometer. c.    Excessive    generator load. d. Dirty    compressor. e.   Gas   producer   fuel control    idle    adjustment incorrectly   set. f.   Air   sensing   lines l^eaking. g.   Accumulator   leaking. a.  Disconnect  the  fuel  line  at  the fuel  nozzle;  flush  system  with  clean fuel.  Replace  the  fuel  control  fuel filter.  (Refer  to  para  5-12.)  If  the same   condition   still   exists,   replace control.  (Refer  to  para  5-12.) b. Refer  to  para  5-12. a.   Correct   leak(s),   then   test   in accordance  with  para  5-8. b.  Replace  double  check  valve. c.  Check  Pg  port  in  the  governor and  the  Pc  port  in  both  control  and governor.  Replace  control  or governor   if   contaminated.   (Refer   to para  5-12  and  5-13.) d.   Isolate   the   governor   from   the system   by   removing   the   tee   fitting from  the  governor  Pc  port  and capping  the  governor  end  of  the  tee. Plug  the  open  governor  port  to prevent   entry   of   dirt.   Start   the engine   and   carefully   accelerate   to 100%  N2  and  check  stability.  If  the engine   is   unstable,   replace   the   fuel control;   if   stable,   replace   the governor.  (Refer  to  para  5-12  and 5-13.) e.    Replace    accumulator(s). f. Clean  or  replace  the  filter.  (Refer to  para  5-12.) a.   Check   lever   position   and   rigging. (Refer  to  para  5-12.) b.  Replace  tachometer.  (Refer  to  TM 55-1520-228-23.) c.   Reduce   electrical   load requirement. d.   Clean   compressor   and   bleed valve.  (Refer  to  para  7-3  and  7-7.) e.   Adjust   idle   setting,   (Refer   to   para 5-12.) f.   Check   for   leaks.   Tighten   coupling nuts   as   required. g.  Check  for  cracks  in  sheet  metal or   braze.   Replace   accumulator   if leaks  are  found.  (Refer  to  para  5-16.) Change   23   4-5 If a crack in sheet metal or braze is suspected, refer to TM 1-1520-254-23, Technical Manual Aviation Unit Main- tenance (AVUM) and Aviation Intermediate Maintenance (AVIM) Manual Nondestructive Inspection Procedure for OH-58 Helicopter Series at  idle.