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Page Title: Adjustment Procedure With Exhaust Analyzer
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ENGINE DIVISION SERVICE MANUAL TM 5-4210-230-14&P-1 ADJUSTMENT PROCEDURE c. Install    new    idle    limiter    caps    with    tab    fully counterclockwise against stop. d. Make  idle  speed  adjustment  per  Step  4  and  to obtain recommended setting for optimum exhaust emission control. 7. If   idle   speed   with   automatic   transmission   in “DRIVE” is     less     than     550     RPM     after     the     above adjustments  have  been  made,  readjust  idle  speed  screw to obtain 550 RPM in “DRIVE.” 8. Disconnect tachometer from engine. Adjustment Procedure With Exhaust Analyzer If  exhaust  analysis  equipment  is  available,  the  following procedure can be used to establish the recommended idle settings.      Exhaust   analysis   equipment   must   have   a “Percent     of     Carbon     Monoxide” meter     which     gives accurate readings in the 0-5% CO range. NOTE: Exhaust analysis equipment is not recommended  for  use  with  winter  grade  gasolines. These  fuels,  being  more  volatile,  yield  vapors  which can  cause  excessively  rich  analyzer  meter  readings. Where winter grade fuels are used, it is recommended    that    the    Speed    Drop    Method    be utilized to obtain correct idle mixture settings. 1. Connect test tachometer to engine. (Tachometer  should  have  an  expanded  scale  of 400-800     or     1-1000     RPM     and     1%     to     2% accuracy.) 2. On  engines  equipped  with  air  injection  system, disconnect  air  injection  hoses  from  air  manifold check valves. 3. Adjust  idle  mixture  screws  full  rich  against  tab stop by turning screws counterclockwise “out.” NOTE:  If  working  with  a  unit  rebuild  which  has  not had idle limiter caps installed, refer to specifications for the initial idle setting. 4. Operate engine until it reaches normal operating temperature. 5. Adjust  idle  speed  screw  to  obtain  specified  idle speed. 6. Prepare   exhaust   analyzer   and   insert   exhaust sample  probe  into  vehicle’s  tail  pipe.    (Refer  to test   equipment   manufacturer’s   instructions   for preparation and hook-up procedures.) 7. Observe   percent   of   carbon   monoxide   (%   CO) indicated on analyzer dial. a. Adjust   idle   mixture   screws  “in”   (clockwise)   by 1/16   turn   increments   to   obtain   specified   CO setting.  (See Carburetor Specifications.) b. Readjust idle speed if necessary and readjust mixture screws    to    provide    the    specified    CO    setting    at specified curb idle speed. NOTE: If working with unit rebuild, install idle limiter caps at this time. 8.   If specified CO setting cannot be obtained per Step 7, it will be necessary to remove the plastic idle limiter caps and establish proper mixture screw setting as follows: a. Remove  limiter  caps.    To  prevent  damage  to  screw threads or seat, file or grind away the side of the cap. Do not pry cap off. b. With engine operating, adjust mixture screws to obtain “lean best idle”  at specified curb idle speed. (“Lean  best  idle”  is  the  point  at  which  engine  speed drops approximately 10 RPM due to leanness.) c. Install new idle limiter caps with tab fully counterclockwise against stop. d. Make  idle  mixture  adjustment  per  Step  7  to  obtain recommended CO setting. 9.   If idle speed with automatic transmission in   “DRIVE” is less than 550 RPM after the above adjustments have been made, readjust idle    speed screw to obtain 550 RPM in “DRIVE.” 10. Disconnect test equipment from engine.   Reconnect air injection hose to air manifold  check valves where equipped. If  unsatisfactory  idle  operation  persists  after  completing  idle adjustment per the above procedures, recheck ignition system components,   timing   advance,   crankcase   ventilation   system and air induction system. Accelerating Pump Lever Adjustment 1. Using a feeler gauge and with the throttle plates in the wide-open position, there should be the specified  clearance  of  .015”   minimum  between  the accelerating  pump  operating  lever  adjustment  screw and the pump arm when the pump arm is depressed manually (Fig.  55). 2. If adjustment is required, loosen the adjusting screw lock  nut  and  turn  the  adjusting  screw  in  to  increase the   clearance   and   out   to   decrease   the   clearance. One-half   turn   of   the   adjusting   screw   is   equal   to approximately .015”. CGES-125-T Page 37 PRINTED IN UNITED STATES OF AMERICA ENGINE DIVISION SERVICE MANUAL TM 5-4210-230-14&P-1 ADJUSTMENT PROCEDURE

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