TM 5-6115-590-12 using   new   gasket.      Tighten   securely   and   reconnect wiring harness connector. 4-82. Oil Pump Filter Element a. Removal.  Unscrew filter case (fig. 4-47) from oil pump assembly without removing pump assembly from engine.        Remove    and    discard    filter    element    and packings. b. Cleaning and Inspection. (1)   Clean filter case with an approved cleaning solvent and dry thoroughly with filtered compressed air. (2)   Visually     inspect     filter     case     for     cracks, corrosion,  damaged  threads  or  other  obvious  damage. Replace damaged filter case. c. Installation.  Dip new replacement filter element in oil of the same specification and brand being used in engine     lubrication     system.          Install     small     packing included with filter element in place inside neck of filter element.  Install new filter element with new packing into case.      Install   case   with   new   element   on   oil   pump assembly.  Tighten case securely, but do not overtorque case. 4-83. Pressure Relief Valve a. Removal.  Without removing oil pump assembly from  engine,  unscrew  pressure  relief  valve  (fig.  4-47) from oil pump assembly.  Remove valve assembly and packings. b. Cleaning and Inspection. (1)   Clean pressure relief valve with an approved    cleaning    solvent    and    dry    thoroughly    with filtered compressed air. (2)   Visually  inspect  valve  assembly  for  cracks, corrosion, abrasion, damaged threads or other evidence of damage. c. Installation.    Install  satisfactory  or  replacement pressure  relief  valve  in  oil  pump  assembly  using  new packing. d. Adjustment.  Check operation of valve assembly during engine operation.  Oil pressure shall be 90  ±  10 psig.  Adjust pressure by loosening lock- nut an-turning adjustment screw as required.  Refer to paragraph 4-14 for instructions on connecting engine analyzer to engine. 4-84. Tachometer Generator a. Removal. (1)   Without removing tach-generator (fig. 4-47) from engine, detach wiring harness connector from tach- generator. (2)   Remove   four   attaching   nuts   and   washers and   carefully   remove   tach-generator   from   oil   pump assembly.  Remove and discard gasket. b. Cleaning and Inspection (1)   Remove   all   dust,   dirt   and   foreign   matter from tach-generator with filtered compressed air. Clean tach-generator   with   a   clean   rag   moistened   with   an approved cleaning solvent and dry thoroughly. (2)   Inspect  electrical  connector  for  damage.    If connector    is    damaged    beyond    repair    replace    the tachometer generator. (3)   Functionally inspect tach-generator in accordance  with  Military  Specification  MIL-G-6027.  If  it fails to meet functional inspection requirements, replace the tach-generator. c. Installation.    Install  satisfactory  or  replacement tachometer   generator   on   oil   pump   assembly   using   a new   gasket   Secure   with   attaching   washers   and   nuts. Tighten   nuts   securely   and   reconnect   wiring   harness connector. 4-85. Low Oil Pressure Switch a. Removal.    Remove  tube  assembly  and  wiring harness   connector   from   low   oil   pressure   switch   (fig. 4-48).    Remove  two  attaching  bolts  and  washers  and remove switch from engine. b. Cleaning and Inspection. (1)   Clean   switch   with   a   clean   rag   moistened with an approved cleaning solvent. (2)   Visually inspect switch for cracks, damaged threads or other evidence of damage. c. Test. (1)   Check the continuity across receptacle pins. Circuit  across  pins  A  and  B  should  be  closed;  circuit across pins B and C should be open. (2)   Place  switch  in  a  suitable  holding  device. Slowly apply filtered, regulated compressed air to switch inlet port. (3)   Check    continuity    across    receptacle    pins while applying air pressure.  Before 45 psig air pressure is  reached,  the  circuit  across  pins  A  and  B  should  be open and circuit across pins B and C should close. (4)   Slowly  decrease  air  pressure.    At  37    ±   3 psig  air  pressure,  circuit  across  pins  A  and  B  should close; circuit across pins B and C should open. (5)   Disconnect   air   supply   and   remove   switch from holding device. d. Installation (1)   Install  replacement  or  satisfactory  switch  in place   and   secure   with   attaching   washers   and   bolts. Tighten bolts to 20 to 25 inch-pound torque. (2)   Reconnect tube assembly and wiring harness connector to switch. 4-86. Centrifugal Multi-Speed Switch Assembly a. Removal.  Disconnect wiring harness connector from    switch    assembly    (fig.    4-41).        Remove    four attaching nuts and washers and carefully remove switch assembly  and  packing  from  engine  in  a  straight  line. Discard packing. 4-103