TM 10-3930-671-24 Injection Pump WARNING Before    disconnecting    lines,    be    sure    to    relieve    all pressure.    Before  applying  pressure  to  the  system,  be sure  all  connections  are  tight  and  that  lines,  pipes,  and hoses   are   not   damaged.      Use   a   piece   of   cardboard, rather  than  hands,  to  search  for  leaks.    Escaping  fluid under pressure can have sufficient force to penetrate the skin, causing personal injury. If injured by escaping fluid, get medical attention at once. The fuel injection pump, flange mounted to the engine, is a compact, self-contained, distributor-type unit incorporating  a  sensitive  all-speed  governor.    It  has  a relatively   simple   design   that   utilizes   no   ball   or   roller bearings, gears, or highly-stressed springs.  The number of   working   parts   remains   the   same   regardless   of   the number of cylinders the pump is required to serve. It  is  constructed  to  be  oil  tight.    During  operation,  all moving  parts  are  lubricated  and  cooled  by  fuel  under pressure.    No  additional  lubrication  system  is  required. Pressure  maintained  within  the  pump  housing  prevents the ingress of dust, water, or other foreign matter. Fuel injection is effected by a single element having twin opposed  plungers  located  within  a  transverse  bore  in  a central  rotating  member.    This  acts  as  a  distributor  and revolves in a stationary member known as the hydraulic head.  The pump  plungers  are  actuated  by  lobes  on  an internal   cam   ring.      Fuel   is   accurately   metered   to   the pumping   element,   and   the   high-pressure   charges   are distributed to the engine cylinders at  the  required  timing intervals   through   ports   in   the   rotor   and   the   hydraulic head. The  internal  cam  ring,  mounted  in  the  pump  housing, operates    the    opposed    pump    plungers    through    cam rollers  carried  in  shoes  sliding  in  the  rotor  body.    The plungers are forced inwards simultaneously as the rollers contact the diametrically-opposed cam lobes.  This is the injection stroke.  The plungers are returned by pressure of  the  in  flowing  fuel  during  the  charging  stroke.    The pump  rotor  is  driven  by  the  engine  through  pinned  hub and gear. Most pumps have an automatic device  which  varies  the point of commencement of injection. The single pumping element ensures uniform delivery of fuel  to  each  cylinder,  and  eliminates  having  to  balance the  deliveries  from  each  of  the  high-pressure  delivery lines. The   integral   governor   is   a   mechanical   flyweight   type which  gives  accurate  control  of  engine  speed  under  all load   conditions.      The   governor   flyweight   assembly   is mounted   on   the   drive   shaft   and   is   contained   entirely within the pump body.  Linkage transmits the movement of  the  governor  flyweights  to  the  control   lever   on   the metering   valve.      The   governor   control   mechanism   is enclosed in a housing mounted on the pump body. Injection Pump Overhaul Dismantling,   assembly,   testing,   and   adjustment   of   the injection pump must be carried out by trained personnel, using specialized tools and test apparatus. Timing Of Injection Pump To The Engine Injection   pumps   must   be   installed   on   the   engine   in accurate alignment and timed to correct relation with the engine    crankshaft    for    proper    engine    operation    with maximum power and economy and to prevent complaints of hard starting, overheating, uneven running, and excessive smoking. Timing a fuel injection pump to a diesel engine is similar to,  and  simpler  than,  timing  a  gasoline  engine  ignition system.    Both  require  precision  to  ensure  the   correct timing as recommended by the engine manufacturer. F-206