ENGINEMAN  1  &  C and   the   manufacturer.   The   following   brief description  of  the  procedures  for  equipment  made by two different manufacturers emphasizes some of these similarities, and further emphasizes the need for following only the procedures indicated in  the  appropriate  manufacturer’s  technical manual. A plunger of a Bosch fuel injection pump can be loosened by cleaning. However, if the plunger does not slide freely in the barrel, both the plunger and barrel should be cleaned with an approved cleaning fluid, rinsed in clean fuel oil, and blown dry with compressed air. A small quantity of mut- ton tallow should then be placed on the plunger. Working the plunger back and forth and rotating it in the barrel should remove all gummy deposits. Instructions for Bosch fuel injection equipment state that such items as hard or sharp tools or abrasives of any kind should never be used in cleaning the pumps. Freeing the sticking plunger in a GM unit in- jector may be done in much the same manner as in a Bosch pump. Stains on plungers may be removed by the use of a limited quantity of jewelers’ rouge on a piece of soft tissue paper. It is important to remember that  the  plunger  should  not  be  lapped  to  the bushing with an abrasive such as jewelers’ rouge. After a plunger has been cleaned with jewelers’ rouge,  it  must  be  cleaned  thoroughly  with  diesel fuel before being placed in the bushing. If after repeated cleanings, the plunger still does not slide freely, you may assume that either the plunger or the bushing is distorted. The  principal  difference  in  the  cleaning  pro- cedures for these two units of equipment is in the use of abrasives. If the recommended cleaning procedure  for  these  units  fails  to  loosen  the plunger so it will slide freely, the plunger and its mating part will have to be replaced. Broken Plunger Spring A  pump  of  an  injector  will  fail  when  the plunger  spring  breaks  and  fails  to  return  the plunger after injection has occurred. Factors which contribute to broken plunger springs   are failure   to   inspect   the   springs thoroughly and careless handling. Broken plunger springs must be replaced. Also they should be replaced when there is evidence of cracking,  chipping,  nicking,  weakening  of  the spring, excessive wear, or when the condition of the spring is doubtful. Jammed  Fuel  Control  Rack If an engine is to operate satisfactorily, the fuel control rack must be completely free to move. Since  the  rack  controls  the  quantity  of  fuel injected per stroke, any resistance to motion will result in governing difficulties. When this occurs, the engine speed may fluctuate (decreasing as the engine is loaded; racing as the load is removed), or the engine may hunt continuously or only when the  load  is  changed.  If  the  fuel  control  rack becomes jammed, it may become impossible to control the engine speed with the throttle. The engine may even resist securing efforts under such conditions. Since a sticking fuel control rack can cause serious difficulty, especially in an emer- gency, every effort should be made to prevent its occurrence. The best way to check for a sticking fuel control rack is to disconnect the linkage to the governor and attempt to move the rack by hand. There should be no resistance to movement of  the  rack  when  all  springs  and  linkages  are disconnected. A fuel control rack may stick or jam as a result of  a  stuck  plunger,  dirt  or  paint  in  the  rack mechanism, a damaged rack or gear, or improper assembly. When this jamming or sticking occurs, it is necessary to determine the cause of binding. If it is due to damage, the damaged parts must be replaced; if the stickiness is due to the presence of dirt, a thorough cleaning of all parts will prob- ably  correct  the  trouble.  Avoid  errors  in reassembly and adjustment by carefully studying the instructions. Backlash in the Control Rack Backlash,  looseness,  or  play  in  the  fuel  con- trol rack, like sticking or binding of the rack, will influence   governing   of   the   engine.   Proper governing is based on the theory that for every change in speed of the engine, there will be a cor- responding change in the quantity of fuel injected. 3-20