TM  5-2815-241-34&P FUEL PUMP CALIBRATION - CONTINUED ACTION LOCATION ITEM REMARKS PUMP SEAL TESTING 25.  Test  stand  (1) Fuel  pump  (2) Check oil seals for leaks as follows: a. With test stand operating at 500 rpm, close  suction  valve  (3). b. Place  fuel  flow  control  valve  (4)  to  OPEN position. If 25-inch (83.5 mm) vacuum is not obtained, check all test stand hose connections. c. Place  bypass  valve  (5)  in  closed position. d. Place a small amount of extreme- pressure  grease  over  the  vent  of  weep hole  (8). e. If extreme-pressure grease is pulled into weep hole (8) at 25-inch (83.5 mm) vacuum,  the  seal  is  defective. To  replace  seal,  see  Fuel  Pump, page  2-289. CAUTION Do not hold throttle lever in idle position any longer than necessary to complete test. Pump may overheat, since fuel flow is used to cool the pump. 28. Fuel  pump  tachometer Check  as  follows: drive  seal  (7) a. With  test  stand  (1)  operating  at  500 rpm,  remove  tachometer  drive  cap  (8). Depress  and  release  FAST  (9)  or SLOW  (10)  button  to  maintain  500 rpm. b. Fill tachometer seal bore with test oil or diesel  fuel  from  test  stand  (1). c. If fuel is drawn into pump at 25-inch (83.5  mm)  vacuum  setting,  the  seal  is defective. To  replace  seal,  see  Fuel  Pump, page  2-289. GOVERNOR  CUTOFF  RPM  TESTING NOTE Test stand must be shut off to change shims in spring pack. When pump is opened to make adjustments, it must be purged of air before retest. With fuel pump at 2100 rpm, move throttle back and forth until the rotameter shows no air. 2-340