TM 10-3930-671-24 General A. PURPOSE OF THE MANUAL This  manual  is  expressly  intended  to  provide  sufficient information    for    qualified    technicians    experienced    in diesel     engines     and     diesel     injection     equipment,     to disassemble  and  reassemble  the  Roosa  Master  DB2- type  fuel  injection  pump  and  to  make  such  adjustments and   parts   replacements   as   may    be    needed.        It    is recommended that an inexperienced person refrain from making   adjustments   and   repairs,   as   such   action   may result    in    very    extensive    damage    to    the    pump    and possibly to the engine. No  service  should  be  performed  on  the   pump   before making  a   careful   study   of   this   manual   and   becoming familiar with the principles and instructions which follow. Since  several  critical  adjustments  of  the  injection  pump are   required   which   cannot   readily   be   made   on   the engine, it is necessary that the service be performed in a facility   equipped   with   the   proper   special   tools   and   an approved, motorized test stand. This manual completely describes the operating principles   of   the   pump   and   most   accessories.      Only through  a  thorough  knowledge  of  these  principles  can the  serviceman  locate  and  correct  possible  operational defects. B. MODEL NUMBER SYSTEM It is necessary to understand the model number system for   reference   to   the   proper   sections   of   this   manual covering operation and maintenance of the pump. EXAMPLE: a b c d e Model Number    DB2 6 33 JN 3000 a. DB2-D Series Pump, 13-Rotor, 2nd generation b. 6-  Number  of  cylinders.    (Available  in  2,  3,  4,  6 and 8 cylinder configurations.) c. 33- Abbreviation of plunger diameter. 25-.250"(6.35mm) 31- .310’"(7.87mm) 27- .270"(6.86mm) 33- .330"(8.38mm) 29- .290"(7.37mm) 35- .350"(8.89mm) d. JN -Accessory code (See S.B.  No.  63) The   code   pertains   to   combinations   of   special accessories such as electrical shutoff, automatic advance,  variable  speed  droop  adjustment,  etc. See the proper service bulletin or manual section for operation and construction of these accessories. Include this in any reference to the pump. e. 3000 - Specification Number Determines  selection  of  parts  and  adjustments for a given application.  Must be included in any reference to the pump. NOTE Pump   rotation   and   method   of   mounting   are   provided under special notes on individual pump specifications. C. GENERAL INFORMATION In a diesel engine, air is drawn into the cylinder through the intake valve and compressed.  A metered quantity of fuel    is    then    injected    into    the    cylinder,    producing    a combustible  mixture.    This  mixture  ignites  from  heat  of compression,  and  the  expanding  gases  force  the  piston downward. The    function    of    a    diesel    fuel    injection    pump    is    to accurately  meter  and  deliver  fuel  to  a  nozzle  in  each cylinder    and    to    inject    it    at    high    pressure    into    the combustion  chamber  at  precisely  timed  intervals.    The extreme   precision   necessary   can   well   be   appreciated since this cycle must be repeated thousands of times per minute  with  virtually  no  variation  in  timing  or  amount  of fuel injected.  The injection pump is truly the heart of the diesel engine. ROOSA MASTER MODEL DB2 DIESEL INJECTION PUMP The   model   DB2   injection   pump   is   described   as   an opposed-plunger,    inlet-metered,    positive-displacement, distributor-type  pump.    The  DB2  pump  incorporates  a single pumping chamber. Simplicity, the prime advantage of Roosa Master design, contributes to lower initial  cost,  greater  reliability,  ease  of  service  and  lower maintenance cost. The necessity for cost reduction is more apparent in the small    diesel    engine    where    the    injection    equipment represents  a  greater  percentage  of  the  cost.    Since  the basic  model  has  but  100  odd  parts,  and  only  four  main rotating    members,    there    is    less    chance    of    failure. Repairs are generally inexpensive.  Today’s small, high- output  engines  have  created  a  need  for  improved,  yet low  cost,  injection  equipment  capable  of  higher  speed operation, quieter running and lower exhaust emissions. F-212

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