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Jammed  Fuel  Control  Rack
Table  3-1.Troubleshooting  Chart-Governor

Engineman 1 & C - Advanced engine mechanics training manual
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Chapter  3—ENGINE  MAINTENANCE This is impossible if backlash, looseness, or play exists in the control system. Continuous or inter- mittent movement of the rack may indicate ex- cessive looseness. Engine speed variations are also indicative of this problem. Note that even though these symptoms are characteristic of a loose rack, a governor which is dirty or out of adjustment will present similar symptoms. Backlash in a fuel control system is generally due to a wornout gear, rack, or control sleeve. When you disassemble a pump or injector for overhaul be sure to inspect all parts of the con- trol system for signs of excessive wear. If the rack may be moved more than a prescribed amount without moving the plunger, find the parts that are worn, and replace them. Improper   Calibration When improper calibration (balance) of fuel injector pumps or injectors occurs, there is a dif- ference in the amount of fuel injected into each of  the  cylinders.  If  some  pumps  or  injectors deliver  more  fuel  per  stroke  than  others,  the engine  will  be  UNBALANCED;  that  is,  some cylinders will carry a greater load than others. This condition  may  be  detected  by  differences  in cylinder   exhaust   temperatures   and   firing pressures,  and  by  smoky  exhaust  from  the overloaded  cylinders.  Roughness  in  operation  and engine   vibration   are   also   indicators   of   an unbalanced    condition. It is important to remember that many other types  of  engine  difficulties  may  cause  engine symptoms identical with those due to unbalance. So  when  unbalance  is  suspected,  consider  first  a few of the other faults that may be present such as  poor  condition  of  piston  rings,  inaccurate exhaust pyrometers and thermocouples, mistimed or faulty engine exhaust or inlet valves. Improper Timing Improper timing of a fuel system will result in uneven operation or vibration of the engine. Early timing may cause the engine to detonate and lose power. Cylinders which are timed early may show  low  exhaust  temperatures.  Late  timing usually  causes  overheating,  high  exhaust temperatures, loss of power, and smoky exhaust. Although,  usually,  improper  fuel  injection timing is caused by failure to follow the manufac- turer’s instructions for timing, there may be other causes  for  the  difficulty,  depending  upon  design of  the  particular  systems.  For  example,  fuel injection time in the injection pump of a Bosch system may get out of time because of a worn pump camshaft. The same problem may occur when  the  adjusting  screw  on  the  injector  control rack of a GM system becomes loose. Either of these conditions will change fuel injection timing. Faulty  calibration  and  improper  timing  are generally  due  to  failure  to  follow  instructions given in the engine technical manual and the fuel injection  equipment  maintenance  manual.  These manuals  should  always  be  consulted  and  fol- lowed whenever timing or calibration difficulties arise. GOVERNORS To control an engine means to keep it run- ning at a desired speed, either in accordance with, or regardless of, the changes in the load carried by  the  engine.  The  degree  of  control  required depends on two factors: The engine’s performance characteristics and the type of load which it drives. In diesel engines the speed and power output of the  engine  is  determined  by  varying  the  amount of fuel that is injected into the cylinders to con- trol combustion. There are two principal types of governors: hydraulic and mechanical. Hydraulic Governors It is beyond the scope of this training manual to list all of the possible troubles which may be encountered with a hydraulic governor. This sec- tion deals only with the most common ones. Poor regulation of speed may be due to the faulty ad- justment of the governor or to faulty action of an engine, a generator, a synchronizing motor, a voltage regulator, or any piece of equipment which has a direct bearing on the operation of the engine. Manufacturers  state  that  50%  of  all  governor troubles are caused by dirty oil. For this reason, 3-21







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