CHAPTER 13 HYDRAULIC ACTUATOR, SUMP AND FILTER REPAIR INSTRUCTIONS Section I. HYDRAULIC ACTUATOR (CLASS I, PRECISE SETS ONLY) 13-1.    General. The  hydraulic  actuator  (figures  13-1  and  13-2)  is  part of   the   generator   set   electro-hydraulic   governing system  (para.  7-1  and  7-2)  and  is  used  to  control  the speed   of   the   generator   set.   An   error   voltage   sensed by   the   governor   system   control   unit   is   magnetically amplified   to   control   the   power   to   energize   the   sole- noid   of   the   hydraulic   actuator,   thus   changing   the high   pressure   input   oil   into   a   differential   pressure across  the  piston. This   is   accomplished   by   a   sole- noid   controlled   teeter   bar   within   the   actuator   that controls   the   position   of   the   actuator   piston. 13-2.   Malfunction. A   malfunction   of   the   hydraulic   throttle   actuator   is usually   indicated   by   engine   shutdown   or   overspeed when  the  START-  STOP-RUN  switch  is  transferred from  the  START  to  the  RUN  position,  frequency drift   observed   on   the   frequency   meters,   sluggish response   to   load   changes,   or   no   response   to   load changes.   To   isolate   the   malfunction,   proceed   as follows a.  Check  for  4-6  Vdc  at  test  points  AB  and  CD (see   figures   1-4   and   1-5)   of   electric   governor   control unit   (A   and   D   are   positive),   with   engine   operating.   If voltage   at   either   point   is   approximately   15   volts,   the malfunction  is  a  result  of  an  opening  in  an  actuator valve   coil,   or   connecting   circuit. b.   Check   that   the   throttle   linkage   (see   figure   13-1) is  not  badly  worn  or  disconnected.  A  worn  linkage can   cause   sluggish   response   or   drifting   frequency.   A disconnected   or   broken   linkage   can   cause   overspeed, shutdown,   or   no   response.   Also   check   linkage   for binding  due  to  dirt  or  distortion. c.   Check   condition   of   hydraulic   filter   and   the   lev- el  of  hydraulic  oil. Either   a   clogged   or   dirty   filter or   low   oil   level   can   reduce   the   hydraulic   pressure required   to   operate   the   actuator. d.   Check   pressure   output   of   hydraulic   actuator by  removing  plugs  in  ports  Al  and  A2  and  inserting 0-400   psi   range   gages. The   pressure   at   each   port should  be  160  +  25  psi  and  equal,  with  engine  operat- ing   under   governor   control.   Operating   under   manual control,   with   J6   disconnected,   the   pressure   at   port A2 should be 180  +  20  psi  and  approximately  50  psi higher   than   the   pressure   at   port   Al. e.  Check  the  transducer  in  the  actuator  far  free- dom   of   movement.   The   transducer   must   move   freely for   good   response. f.   If   any   of   the   above   examinations   indicates   that the–actuator   has   failed,   proceed   with   removal,   dis- assembly   and   repair   instructions. 13-3.   Removal   and   Disassembly. a.   Clean   all   hydraulic   fittings   and   couplings throughly   to   prevent   contamination   of   system b.   Remove   drain   plug   on   bottom   of   hydraulic sump   and   drain   and   discard   hydraulic   oil   (Refer   to Operator   and   Organizational   Maintenance   Manual   for draining    procedures.) c.   Remove   hydraulic   actuator   as   illustrated   in figure  13-1. d.   Remove   four   bolts   securing   bracket   to activator   and   remove   bracket. 13-2 f . wires 13-4. a. Disassemble   actuator   as   illustrated   in   figure To  remove  connector  (34)  tag  and  unsolder  all attached   to   connector. Cleaning,   Inspection   and   Repair. Clean   all   parts   thoroughlv   with   cleaning solvent   Federal   Specification^-P-D-680   and   dry thoroughly. b.  Inspect  all  parts  for  damage  or  defective condition. co wear. d. age; e. — 13-5. a. ted  in b. Inspect Inspect ball   joints   and   linkage   for   excessive actuator   packing   and   piston   for   dam- Replace   all   defective   parts. Reassembly   and   Installation. Reassemble   the   hydraulic   actuator   as   illustra- figure   13-2. Install   set   screw   (37)   in   core   assemblv   (40) finger    tight. Then   install   locknut   (36).   Proceed with  care. C.   When   installing   connector   (13),   locate   keyway at   12   o’clock   position.   (See   figure   13-2.) d.   When   installing   connector   (34),   locate   keyway at  6  o’clock  position,  viewed  from  top  of  valve  block (48).   (See   figure   13-2.) 13-6.   Actuator   Valve   and   Piston   Test. 13-1