diaphragm   is   faulty   and   the   complete   secondary   diaphragm assembly should be replaced. Figure 69 Vacuum Connection for Checking Secondary Control Valve Diaphragm 1.  Air Filter (Where Used) 4. To Vacuum Source (6” G) 2.  Diaphragm Chamber 5. Not Used When Air Filter 3.  Adapter Fitting is Used 2.    Connect   the   vacuum   source   to   the   venturi   vacuum pickup passage on the back of the cover assembly, as shown in Fig.  70.  Tightly cover the fresh air passage also on the back of the cover assembly.  Apply 6 inches of vacuum. If secondary diaphragm moves (compresses   spring)   and   vacuum   holds,   secondary diaphragm is satisfactory.  If diaphragm does not move or     if     vacuum     cannot     be     maintained,     secondary diaphragm is faulty P-d should be replaced. 3.    With vacuum applied as in Step 2, uncover the fresh air passage.    If  vacuum  holds,  control  valve  needle  and seat are satisfactory.  If vacuum cannot be maintained, control   valve   is   faulty   and   the   complete   secondary diaphragm assembly should be replaced. On the Vehicle Test The “on the vehicle”  test outlined below can be used to help locate the cause for loss of governor control. 1.    With   the   vehicle   on   the   service   floor   accelerate   the engine to check governor operation. a.      Governor   should   limit   engine   speed   to   150-250   initial overrun.  Adjust governor if necessary. Figure 70 Vacuum Connection for Checking Secondary Control Valve and Diaphragm 1. To Check Diaphragm Cover Passage To Check Needle and Seat Uncover Passage 2.     Air Filter 6.  Hose .125 I.D. (Where Used) 7.  Tube .125 O.D. 3. To Vacuum Source 8.  Gasket (6”  HG) 9.  Fresh Air Passage 4. Venturi Vacuum Passage 5. Vacuum Passage NOTE: Initial overrun means that under acceleration  the  engine  will  momentarily  exceed governed  speed  by  approximately  150-250  RPM and then settle to governed speed. b.     If  there  is  no  governor  control,  proceed  with Step No.  2 below. c.     If  the  engine  governs  at  light  load  and  does not govern at wideopen throttle, the problem is probably    in    the    secondary    control    valve. Proceed with Step No.  4 below. 2.    Disconnect the vacuum line (distributor to governor throttle actuating unit) from the fitting at the governor unit.  Leave the secondary control valve vacuum line connected.  Operate the engine at 2200 RPM, wet your finger and hold it over the opening in the fitting. If the engine speed slows to approximately 1000 RPM, the governor trouble is in the governor control (“spinner”) valve or the lines or connections to the governor control valve.  If the engine does not slow down, proceed with Step No.  3. CGES-125-T Page 44 PRINTED IN UNITED STATES OF AMERICA ENGINE DIVISION SERVICE MANUAL TM 5-4210-230-14&P-1 TROUBLE SHOOTING 3.     Disconnect the secondary control valve vacuum line from   the   fitting   and   remove   the   fitting.      Again, operate  the  engine  at  2200  RPM  and  place  a  wet finger   over   the   vacuum   passage   in   the   governor throttle unit. If the engine now slows to approximately   1000   RPM,   the   problem   is   in   the secondary  control  valve  or  its  vacuum  line.    If  the engine  does  not  slow  down,  the  problem  is  in  the governor throttle unit or the vacuum passages behind it. 4.    When    the    problem    is    suspected    to    be    in    the secondary  control  valve,  operate  the  vehicle  on  the