TM  55-2840-241-23 Table   4-1.   Troubleshooting   (Continued) Item Trouble Probable    cause Remedy 2 c.   Failed   spark   igniter. (cont) d.   Failed   ignition   exciter. e.   Spark   igniter   firing intermittently. 3 4 5 Engine   fails   to   light off —  vapor   coming out  of  exhaust  and ignition   operation audible. Engine   fails   to   light off —  no  fuel  vapor coming  out  of exhaust. Engine  lights  off  but will  not  accelerate  to idle  speed  in  45 seconds. Water  or  other contaminants    in    fuel. a.  No  fuel  in  tanks. b.   Insufficient   fuel pressure   to   engine   fuel pump. c.  Gas  producer  fuel control  in  cutoff  position. d.   Fuel   pump inoperative. e.  Fuel  nozzle  valve stuck. f.  Fuel  nozzle  orifice clogged. g.  Air  fuel  lines. h.  Fuel  check  valve stuck. a.   Inadequate   starter torque  caused  by  low battery   or   defective starter-generator. c.  Replace  igniter.  (Refer  to  para 5-36.) d.  Replace  exciter.  (Refer  to  para 5-35.) e.  Check  input  voltage  to  exciter,  If voltage  is  low,  check  battery.  If voltage  is  not  low,  replace  exciter. Check  a  sample  of  fuel  from  the bottom  of  the  tank.  If  contaminated, defuel  the  tank  (Refer  to  TM 55-1520-228-23).   Disconnect   fuel line  at  the  fuel  nozzle  then  flush  the system   with   clean   fuel.   Install   new filters  in  the  fuel  pump  and  fuel control. a.   Fill   tanks   with   fuel. b.  Turn  on  aircraft  boost  pump. c.   Check   linkage. d(1).  Check  pump  for  sheared  drives or   internal   damage   and   replace   as required.  (Refer  to  para  5-9). d(2).  Check  for  air  leaks  at  pump e.  Replace  nozzle.  (Refer  to  para 5-15). f(1).  Check  fuel  filter.  (Refer  to  para 5-l0.) f(2).  Replace  nozzle.  (Refer  to  para 5-15.) g.  Bleed  system  and  try  a  second start. h.  Replace  check  valve.  (See  Figure 5-2). a.  Check  condition  of  battery  and starter-generator   to   determine   if sufficient  N1  cranking  speed  is attainable. 4-2 Change 23 b.  Air leaks in control air tubing. b.  Check air tubes and fittings for looseness or cracks. Replace or tighten tubes and fittings as required. If cracked engine mounting pads are suspected, refer to TM 1-1520-254-23, Technical Manual Aviation Unit Maintenance (AVUM) and Aviation Intermediate Maintenance (AVIM) Manual Nondestructive Inspection Procedure for OH-58 Helicopter Series.