• Home
  • Download PDF
  • Order CD-ROM
  • Order in Print
Starter Motor Operates but Does not Crank Engine
Fuel and Oil Purifiers

Engineman 2 - Intermediate engine mechanics training manual
Page Navigation
  79    80    81    82    83  84  85    86    87    88    89  
the pump and the supply tanks. The trouble might be caused by a clogged fuel line strainer or by an air leak in the line. If the wobble pump is pumping, the trouble may  be  in  the  line  to  the  engine  fuel  pump  or  in  the engine  fuel  pump  itself. Check   the   fuel   lines   for   cracks,   dents,   loose connections, sharpbends, andclogging. You can remove the fuel line at the pump and use air to determine if the line is open. Check fuel pumps for leaks at the pump gaskets or in the fuel line connections. Check fuel pump filters or sediment bowl screens for restrictions. Check the bypass for operation. If the bypass valve is defective, replace the fuel pump. In diaphragm-type fuel pumps, the filter bowl gasket, the diaphragm, or the valves may be the source of trouble. Check for air leaks in the diaphragm by  submerging  the  discharge  end  of  the  fuel  line  in gasoline  and  looking  for  air  bubbles  while  cranking  the engine.  If  the  engine  will  run,  a  leaky  diaphragm  is indicated by gasoline leakage from the pump air vent. Carburetor trouble may be the cause if fuel does not reach the cylinders. You can check this by removing the spark plugs and looking for moisture. If there is no trace of gasoline on the plugs, the carburetor may be out of adjustment, the float level may be too low, or the jets may be clogged. If the fuel level in the carburetor float bowl is low, the float valve is probably stuck on the seat. If  the  fuel  level  in  the  float  is  correct,  yet  no  fuel  is delivered  to  the  carburetor  throat,  the  carburetor  will have to be removed, disassembled, and cleaned. Faulty ignition system parts may be the source of starting  difficulties.  You  may  encounter  two  kinds  of ignition  systems-the  MAGNETO  type  and  the BATTERY type. Even though the parts of these systems differ  in  some  respects,  their  function  is  the  same; namely, to produce a spark in each cylinder of the engine at exactly the proper time in relation to the position of the  pistons  and  the  crankshaft.  Also,  the  system  is designed so the sparks in all cylinders follow each other in  proper  sequence. ENGINE FAILS TO STOP If a gasoline engine fails to stop when the ignition switch  is  turned  to  the  OFF  position,  the  trouble  is usually  caused  by  a  faulty  ignition  circuit,  improper timing, the octane rating number of the fuel being too low for the design of the engine, or the engine being overheated. In a magneto-type ignition system, an open ground connection may cause an engine to run after the ignition switch is turned off. When a magneto ground connection is open, the magneto will continue to produce sparks as long as the magneto armature magnets rotate, and the engine will continue to run. In other words, when the magneto ignition switch contact points are closed, the ignition should be SHUT OFF. This is not true of the booster coil circuit of a magneto-type system, nor of the usual battery-type ignition system. In these systems, an open ground or open switch points prevent current flow. If the switch of a battery-type ignition system fails to stop the engine, the contact switch points have probably remained  closed. If  the  ignition  switch  and  the  circuit  are  in  good condition, failure to stop may be caused by overheating. If   the   engine   is   overheated,   normal   compression temperature  may  become  high  enough  to  ignite  the  fuel mixture even though no spark is being produced in the cylinders. When this happens in a gasoline engine, the engine  is,  in  reality,  operating  on  the  diesel  principle. Normally,  you  will  detect  the  symptoms  of overheating before the temperature gets too high. The causes of overheating in a gasoline engine are much the same as those for a diesel engine. Other  troubles  and  their  symptoms,  causes,  and corrections  that  may  occur  in  a  gasoline  engine  are similar  to  those  found  in  a  diesel  engine.  Troubles leading to the loss of rpm, irregular operation, unusual noises, abnormal instrument indications, and excessive consumption or contamination of the lube oil, fuel, or water  can  usually  be  handled  in  the  same  way  for gasoline and diesel engines. Of course, there are always exceptions, so it is best to consult the manufacturer’s technical   manual. Most gasoline engines in the Navy are used by shore activities.  Afloat,  gasoline  engines  are  used  to  drive portable pumps like the P-250, a piece of fire-fighting and  dewatering  equipment.  Although  pumps  like  the P-250  are  primarily  maintained  by  members  of  the Damage  Controlman  (DC)  rating,  Enginemen  are involved  to  some  extent  in  repairing  or  overhauling  the P-250. Before  you  disassemble  a  P-250  for  repair,  make sure that all the repair parts are available and on hand. When repairs are not within your ship’s force capability, you must turn the unit in to an IMA or SRF for repair. Attach an OPNAV 4790/2K (work order form) to the pump. Figure 3-45 illustrates a typical P-250 pump unit. 3-45







Western Governors University

Privacy Statement
Press Release
Contact

© Copyright Integrated Publishing, Inc.. All Rights Reserved. Design by Strategico.