Low oil level in hydraulic governors may be caused by oil leaking from the governor or failure to maintain the proper oil level. Leakage of oil from a governor can generally be traced to a faulty oil seal on the drive shaft or power piston rod, or to a poor gasket seal between parts of the governor case. Check the condition of the oil seals if oil must be added too frequently to governors with independent oil supplies. Oil seal leakage may or may not be visible on external  surfaces.  There  will  be  no  external  sign  if leakage occurs through the seal around the drive shaft, while leakage through the seal around the power piston will be visible. Oil seals must be kept clean and pliable. Store them properly so they do not become dirty or dry and brittle. Leaky   oil   seals   cannot   be   repaired.   They   must   be replaced. You can prevent some leakage troubles simply by  following  proper  installation  and  storage  instructions for the seals. Most   manufacturer’s   technical   manuals   supply information on the governor. Special hydraulic governor maintenance manuals made available by the Naval Sea Systems   Command   are   the   Marquette   Governor Manual,  NAVSHIPS  341-5505  (0341-LP-550-5000), and the Woodward  Governor  Manual,  NAVSHIPS 341-5017 (0341-LP-501-7000). Inoperative Overspeed Safety Devices Overspeed safety devices are designed to shut off fuel  or  air  in  case  of  excessive  engine  speed.  These devices must be maintained in operable condition at all times.  Inoperative  overspeed  devices  may  also  cause  an engine not to start. They may be inoperative because of improper adjustment, faulty linkage, or a broken spring, or  the  overspeed  device  may  have  been  accidentally tripped  during  the  attempt  to  start  the  engine. If  the  overspeed  device  fails  to  operate  when  the engine   overspeeds,   the   engine   may   be   secured   by manually cutting off the fuel oil or the air supply to the engine. Most engines have special devices or valves to cut off the air or fuel in an emergency. Insufficient Cranking Speed If   the   engine   cranks   slowly,   the   necessary compression  temperature  cannot  be  reached.  Low starting air pressure may be the cause of such trouble. Slow cranking speed may also be the result of an increase  in  the  viscosity  of  the  lubricating  oil.  This trouble occurs during periods when the air temperature is  lower  than  usual.  The  oil  specified  for  use  during normal   operation   and   temperature   is   not   generally suitable  for  cold  climate  operation. IRREGULAR ENGINE OPERATION As the engine operator, you must constantly be alert to detect any symptoms that might indicate trouble. Such symptoms may be sudden or abnormal changes in the supply, temperature, or pressure of the lubricating oil or cooling water. Color and temperature of the exhaust may also   indicate   abnormal   conditions.   Check   them frequently. Fuel, oil, and water leaks indicate possible troubles.  Keep  the  engine  clean  to  make  such  leaks easier to spot. You will soon become accustomed to the normal sounds and vibrations of a properly operating engine. If you are alert, an abnormal or unexpected change in the pitch or tone of an engine’s noise or a change in the magnitude or frequency of a vibration will warn you that all is not well. A new sound such as a knock a drop in the fuel injection pressure, or a misfiring cylinder are other   trouble   warnings   for   which   you   should   be constantly  alert  during  engine  operation. The following discussion on possible troubles, their causes, and the corrective action necessary is general rather  than  specific.  The  information  is  based  on instructions for some of the engines used by the Navy and is typical of most. A few troubles listed may apply to  only  one  model.  For  specific  information  on  any particular engine, consult the manufacturer’s technical manual. ENGINE STALLS FREQUENTLY OR STOPS SUDDENLY We discussed earlier several of the troubles that may cause an engine to stall or stop. Such troubles as air in the   fuel   system,   clogged   fuel   filters,   unsatisfactory operation  of  fuel  injection  equipment,  and  incorrect governor   action   not   only   cause   starting   failures   or stalling   but   also   cause   other   troubles   as   well.   For example, clogged fuel oil filters and strainers may lead to a loss of power, to misfires or erratic firing, or to low fuel  oil  pressure.  Unfortunately,  a  single  engine  trouble does not always manifest itself as a single difficulty but may be the cause of several major difficulties. Factors that may cause an engine to stall include misfiring,  low  cooling  water  temperature,  improper application  of  load,  improper  timing,  obstruction  in  the combustion  space  or  in  the  exhaust  system,  insufficient 3-30