ENGINE DIVISION SERVICE MANUAL TM 5-4210-230-14&P-1 a. Operate  distributor  at  300  RPM  and  set  zero  of  test stand  degree  ring  in  line  with  arrow  flash  nearest front of stand. b. Observe  relative  position  of  all  arrow  flashes.    All flashes  should  be  evenly  spaced  within  +  2  degrees at 45 degree intervals on 8-cylinder distributors or 90 degree     intervals     on     4-cylinder     distributors.          If positions   of   arrow   flashes   deviate   more   than   +   2 degrees  check  for  damaged  trigger  wheel  teeth  and check for worn distributor shaft and bushings. 5. Check operation of mechanical advance mechanism as follows: a. With   distributor   operating   at   minimum   speed,   set zero of test stand degree ring in line with arrow flash nearest front of stand. b. Operate distributor at each specified test speed (see DISTRIBUTOR TEST SPECIFICATIONS) and observe   arrow   flashes   opposite   test   stand   degree ring  to  determine  amount  of  advance  at  each  test speed. If  advance  is  excessive,  advance  spring  tension  is  weak.    If advance  is  insufficient,  advance  spring  tension  is  excessive, advance  flyweights  are  sticking  or  trigger  wheel  assembly  is binding   on   inner   distributor   shaft.      If   advance   is   erratic, advance  flyweights  are  sticking  or  trigger  wheel  assembly  is binding on inner distributor shaft. 6. Check  vacuum  advance  diaphragm  assembly  (where equipped) as follows: a. Using   proper   adapter,   connect   test   stand   vacuum hose    to    distributor    vacuum    advance    diaphragm assembly. b. Apply vacuum and check for operation of diaphragm assembly. c. Remove   vacuum   hose   from   diaphragm   assembly. Hold   finger   over   end   of   hose   and   adjust   vacuum regulator  to  obtain  reading  of  16  inches  of  vacuum on vacuum gauge. d. Reconnect vacuum hose to diaphragm assembly and observe vacuum gauge.  If gauge reading returns to 16 inches within a few seconds and holds 16 inches, diaphragm  assembly  is  air  tight.    If  gauge  reading fails  to  return  to  16  inches,  diaphragm  assembly  is leaking and should be replaced. 7.    Check vacuum advance operation (where equipped) as follows: a. With  vacuum  hose  connected  to  distributor  vacuum diaphragm    assembly,    operate    distributor    at    300 RPM. b. With no vacuum applied to diaphragm assembly, set zero of test stand degree ring in line with arrow flash nearest to front of stand. c. Adjust vacuum regulator to apply specified amount of vacuum for each specified check point (see DISTRIBUTOR  TEST  SPECIFICATIONS)  and  note amount of advance obtained. d. Momentarily exceed highest vacuum value specified, then     reduce     vacuum     and     again     note     vacuum obtained at each specified check point. f advance is excessive during both steps "c" and "d", a weak   diaphragm   spring   is   indicated.      If   advance   is insufficient   during   both   steps   "c"   and   "d",   check   for sticking or worn sensor advance plate. 8. If distributor passes checks outlined in Steps 3 through 7 above, it is satisfactory for use.  If distributor fails any of   the   checks,   it   should   be   replaced   or   serviced   as needed. 9. Disconnect test leads and vacuum hose from distributor and remove distributor from test stand. DISTRIBUTOR DISASSEMBLY The    procedure    outlined    below    can    be    followed    to disassemble the distributor for service and overhaul. CGES-145-U  Page 8 PRINTED IN UNITED STATES OF AMERICA