TM 9-2815-225-34&P 3-93.  ON-ENGINE FUEL PUMP ADJUSTMENT (Contd) LOCATION/ITEM ACTION REMARKS 23.     Threaded stud (27) a.  Decrease leakage by turning out until engine (1) tends to stall after deceleration to high idle. b.  Turn in until deceleration is increased 1-2 seconds.  Lock threaded stud (27) with jamnut (28). c.  Recheck idle speed and readjust as necessary. NOTE Engine  power  cannot  be  set  accurately  in  any  other  way  except  on  engine  dynamometer. Fuel pump adjustments must not be made on an engine when the engine power comes from an  estimate.    Before  any  adjustments  on  the  fuel  pump  are  made,  the  following  engine performance data must be checked so that adjustments are justified. 24.     Fuel rail pressure, fuel rate, Check. Under no circumstances should speed setting, smoke, coolant specifications be exceeded. temperature, combustion smoothness, exhaust restriction, fuel quality, air intake restriction, engine oil level, engine power reducing factors h.  Checking Engine Power 25.     Governor speed cutoff Recheck setting point.   Readjust if necessary. i.  Checking Fuel Filter Restriction 26.     Vacuum gauge (30) Connect to fuel inlet (29) Use suitable adapter. on damper (31). 27.     Engine (1) Bring engine (1) to full throttle If restriction reads 8 in. (203 mm) and full load on dynamometer (2) of vacuum while engine (1) is and check vacuum gauge (30). running at full throttle and full load, change fuel filter.  Refer to LO 9-2320-273-12 and LO 9-2320- 283-12.  Also check other sources of restriction.  Use sight glass to check for moving bubbles and pos- sible gasket or other leaks.  If air bubbles are still seen after above checks, check float valve in float tank used for test.  Fuel pump may be pumping more fuel than float valve will allow to pass into the float tank. 3-700