SERVICE MANUAL GENERAL Section 1 Supply Pump With Hand Priming Pump The piston-type supply pump (6, Figure 1) is activated by the eccentric on the injection pump camshaft and serves as  a  mount  for  the  hand  priming  pump  (10,  Figure  1). Since all fuel entering the injection pump must be filtered to ensure long pump life, the hand priming pump should be  used  when  changing  fuel  filters.    Always  install  the fuel  filters  "dry"  and  use  the  hand  pump  to  fill  the  filters and bleed air from the fuel system. Aneroid Assembly Exhaust   smoke   levels   during   engine   acceleration   are controlled   by   using   an   aneroid   (12,   Figure   1).      The aneroid  limits  fuel  delivery  during  acceleration  until  the turbocharger  speed  is  sufficient  to  provide  adequate  air for complete combustion.  An external line connects the intake manifold to the aneroid to allow manifold pressure to activate the aneroid.  A leak in the aneroid diaphragm or intake manifold to aneroid line will cause the injection pump   to   stay   in   the   "cutback"   position,   and   reduce engine power. Fuel Return Valve A  fuel  return  check   valve   is   mounted   to   the   injection pump   housing   (1,   Figure   6)   and   all   fuel   that   is   not injected    passes    through    the    check    valve    and    then through  a  special  orificed  rubber  hose.    The  function  of the fuel return check valve is to provide Figure 6.  Right Side View of Injection Pump 1. Fuel Return Valve 2. Delivery Valve Holder 3. Drive Gear a  positive  seal  to  prevent  fuel  from  draining  out  of  the pump  housing  when  the  engine  is  stopped.    The  fuel return    check    valve    opens    at    approximately    18    psi. Therefore,   total   fuel   flow   through   the   injection   pump housing is controlled by the orifice in the rubber hose as long as the supply pump pressure is above 18 psi.  After the fuel flows through the orifice, the fuel pressure drops from  the  intermediate  pressure  ahead  of  the  orifice  to low pressure (Figure 4). GOVERNOR The mechanical flyweight governor (5, Figure 1) which is mounted  on  the  injection  pump,  is  the  variable  speed type,  identified  by  the  manufacturer  as  ROV  350-1200 (or  -1300).    The  350-1200  (or  -1300)  designation  refers to the injection pump speed range in which the governor functions.    This  corresponds  to  700  to  2400  (or  2600) engine  RPM,  since  the  pump  camshaft  rotates  at  1/2 engine  speed.    Figure   7   illustrates   a   typical   cut-away view of the RQV governor Figure 7.  Cut-Away View of Governor Assembly 1. Stop Shackle 7. S-Plate 2. Rack Link 8. Guide Pin 3. Control Rack 9. Adjusting Pin 4. Governor Springs 10. Guide Lever 5. Bell Crank 11. Rocker Arm 6. Sliding Block 12. Aneroid CGES-375 Printed in United States of America Page 5