ENGINEMAN  1  &  C instruments.   The   instruments   give   the   most reliable  indication  as  to  what  an  engine  is  doing and what adjustments should be made. OIL LINES AND PASSAGES Troubles occurring in the oil passages and oil lines  are  usually  in  the  form  of  plugged  or cracked lines. The former is generally the result of carelessness, while the latter is usually a result of improper support of the line. Even   though   clogged   passages   may   be indicated  by  increased  pressure  gage  readings,  it is  dangerous  to  rely  wholly  on  such  indications, since  stoppage  occurring  beyond  the  pressure regulating valve and pressure gage may cause very little, if any, pressure increase on the gage. You can best determine if a bearing is receiving oil by inspecting   it   occasionally,   just   after   engine shut-down. There should be plenty of oil in the vicinity of the parts being lubricated. Another method for checking bearing lubrication is to note the temperature of the bearings by feeling them with the hand after engine shut-down. You should be able to keep your hand on them for at least a few seconds. 3-16 You can help prevent most oil line stoppage by  observing  the  following  rules: 1. Never use cotton waste or paper towels for cleaning an engine. They may leave lint or small bits of material which later may collect in the lines. 2. Service the oil filters at specified intervals. Clean the case properly and when the lines are removed, blow them out with compressed air. FUEL INJECTION EQUIPMENT AND CONTROLS The fuel system is one of the most complicated of all engine systems; therefore, special care must be  exercised  when  making  adjustments  and repairs. Even  though  manufacturers  have designed many different fuel systems, the basic principle involved is the same in all of them. If you understand the basic principle for one system, you will have no difficulty in becoming familiar with  other  systems.   The  procedures  for  the maintenance and repair of the various systems are also  similar. Let’s review briefly not only the function of a fuel system but also the various types of fuel systems.  As  you  know  the  function  of  a  fuel injection system is to deliver fuel to the engine cylinders  under  specific  conditions:  at  a  high pressure, at the proper time, in the proper quan- tities,  and  properly  atomized.  This  function  may be  carried  out  by  either  one  of  two  types  of systems: the air injection type or the solid injec- tion type. Since there are few air injections systems now  in  use,  we  will  consider  only  the  solid (mechanical)  injection  type  systems. Solid injection systems may be classified as jerk  pump  systems  and  common  rail  systems. Variations  are  to  be  found  in  each  of  these systems.  The  following  examples  show  some  of the basic differences between the various solid injection  systems. Systems  of  the  JERK  PUMP  type  may  be identified as either individual pump systems or unit  injection  systems.  Some  jerk  pump  systems use a separate pump and fuel injector for each cylinder, while the unit injection systems combine the pump and injector into a single unit. The Bosch system is an example of an in- dividual  pump  system.  The  pump  is  a  cam- actuated,  constant  stroke,  lapped  plunger  and barrel pump. The pump times, meters, distributes, and provides the necessary pressure to inject the fuel  into  the  cylinder  through  a  separate  nozzle. The General Motors unit injector is an exam- ple of a unit injection system. It embodies a cam- actuated,  constant  stroke,  lapped  plunger  and bushing,  a  high  pressure  pump,  and  an  injection nozzle, all in one unit. In  the  Cummins  injection  system,  a  cam- actuated  injector  and  nozzle  assembly  is  mounted in each cylinder. This system employs a common metering device that distributes a measured quan- tity   of   fuel   to   each   of   the   injectors.   The Cummings injection system embodies characteristics   of   the   unit   injector   and   is sometimes  classified  as  such,  although  it  is  also called a distributor system. The  Fairbanks-Morse  injection  system  is another example of a jerk pump system. The injection system known as the COMMON RAIL  system  includes  two  types:  the  basic