3-9. What is the main source of fuel pump  and  injection  system  troubles? 1. Contaminated  fuel 2. Improper   adjustments 3. Coated  fuel  lines 4. Excessive   vibration 3-10. Metal fatigue in the nipples of a fuel  system  is  usually  caused  by which  of  the  following  factors? 1. Leakage 2. High  injection  pressure 3. Vibration 4. Erosion 3-11. What are the two main causes of leakage in fuel tanks? 1. Corrosion  and  excessive  fuel line  pressure 2. Metal  fatigue  and  improper welds 3. Vibration  and  metal  fatigue 4. Clogged  fuel  lines  and corrosion 3-12. Which  of  the  following  problems  is likely to cause failure of a diesel engine  mechanical  governor? 1. Faulty  oil  seals 2. Bound  control  linkage 3. Defective  cold  starting  valve 4. Low oil level 3-13. Which  of  the  following  actions  will cause  the  overspeed  safety  device of an engine to become inoperative? 1. Trying to start the engine with low  air-starting  pressure 2. Tripping  the  device accidentally  while  trying  to start the engine 3. Shutting  off  the  fuel  supply after starting the engine 4. Shutting  off  the  air  supply after  starting  the  engine 3-14. Most  diesel  engines  are  equipped with a special means of cutting off their air or fuel supply in an emergency. In which of the following  situations  would  the special means be used? 1. Engine  cannot  be  cranked  or barred  over 2. Parts of the exhaust system are obstructed 3. Fuel  oil  injection  system  is not  properly  timed 4. Overspeed  safety  device  does not  operate  when  speed  becomes excessive 3-15. Slow cranking of a cold diesel engine may be caused by the use of which  of  the  following  substances? 1. Detergent  lube  oil 2. High viscosity lube oil 3. Centrifuged  lube  oil 4. Low viscosity lube oil 3-16. What  diesel  engine  system  is  likely to be at fault if a cylinder misfires  regularly? 1. Lubrication 2. Fuel 3. Exhaust 4. Ignition 3-17. A  cylinder  compression  leak  is indicated when the pressure in a particular  cylinder  of  an  engine signals which of the following conditions? 1. It is much higher than the pressure in the other cylinders 2. It is much lower than the pressure  in  the  other  cylinders 3. It fluctuates from normal to much  below  specified  pressure 4. It fluctuates from normal to much  above  specified  pressure 18