TM  55-4920-400-13 2-40.    Troubleshooting. If  there   is   insufficient vacuum  or  pressure  for  maximum  indications  on  the test   set   instruments,   it   is   necessary   to   determine whether  the  pump  is  at  fault  or  a  leak  exists  in  the lines.  To  check  the  pump,  disconnect  the  pump  lines horn  the  vacuum  and  pressure  fuel  filter  sumps  and connect  these  lines  to  the  altimeter  and  fuel  pressure instruments  respectively.  Refer  to  figure  3-1  for  the vacuum  and  pressure  lines  schematic  diagram.  Turn on the motor and check that 29 inches of vacuum is pro- duced on the vacuum side of the pump and that a min- imum  of  25  pounds  of  pressure  is  produced  on  the  pres- sure side. If the pump produces insufficient vacuum for pressure, the pump is defective and should be replaced. If the pump is capable of proper operation then a leak exists  elsewhere  in  the  tast  set.  All  fittings,  gaskets, lines, and components should be checked for leaks and defective  components  replaced.  In  replacing  a  check valve,  be  sure  to  orient  replacement  valve  with  arrow pointing  in  same  direction  as  arrow  on  original  valve. Faults  in  the  electrical  system  can  be  found  by  per- forming a point-to-point wiring check. Refer to figure 2- 5 for the schematic and wiring diagram on the test set. 2-41.  Rate-of-Climb  Indicator a. Removal. (1) Disconnect  hose  assembly  from  fitting  on rate-of-climb  indicator  (as  instructed  in  paragraph  244. (2)  Remove   the   four   nuts,   Iockwashers,   and screws  securing  rate-of-climb  indicator  to  front  panel. Remove  rate-of-climb  indicator. (3)  Remove  45°  elbow  from  rate-of-climb  in- dicator. b.  Installation (1)  Install  45°  elbow  on  rate-of-climb  indica- tor. (2)  Place  indicator  in  position  on  front  panel and   secure   with   the   four   screws,   lockwashers,   and nuts. (3)  Connect  hose  assembly  to  fitting  on  rate- of-climb indicator. 2-42   Altimeter a.  Removal. Remove the altimeter in a man- ner similar to the way the rate-of-climb indicator is re- moved. b.  Installation. Install   the   altimeter   in   a manner similar to the way the rate-of-climb indicator is installed (para. 2-41). 2-43.  Airspeed   Indicator a.  Removal. Remove  the  airspeed  indicator  in a  manner  similar  to  the  rate-of-climb  indicator  is  re- moved. b.  Installation. Install  the  airspeed  indicator in a manner similar to the way the rate-of-climb indica- tor is installed (para. 2-45). 2-44.  DELETED 2-45.  DELETED 2-46.  Chassis  Assembly a.   Removal. It   is   necessary   to   remove   the chassis  assembIy  from  the  tester  case  in  the  following manner in order to replace components that are on the chassis. (1)  Disconnect  all  hose  and  tube  assemblies which  are  connected  to  components  that  are  mounted on  the  chassis. (2)  Unsolder   electrical   leads   that   are   con- nected to fuseholder and light base. Identify leads to fa- cilitate   installation. (3)  Remove   mounting   nut   securing   power switch tocase and remove switch. (4)  Remove   six   screws   securing   chassis   as- sembly to tester case. b.  Installation (1)  Place   assembled   chassis   in   position   in tester case and secure with the six screws. (2) Solder  leads  on  fuseholder  and  light  base as previously identified. (3)  Place  power  switch  in  position  on  tester case and secure viith mounting nut. (4)  Connect  all  hose  assemblies  to  the  com- ponents that are mounted on the chassis. (5)  Position   wiring   harness   on   tester   case and secure with screws, lockwashers, and nuts. 2-47.  Pressure  and  Vacuum  Filter  Sumps. Remove and disassemble the pressure  and vacuum fil- ter sumps for cleaning and repair, as follows a. Removal and Disassembly. (1)  Remove   tube   assemblies. (2)  Remove   clamp,   bowl,   gasket,   and   filter from filter sump bodies. (3)  Remove   sump   bodies   and   remove   elbows 2-10 Change 2