3-93. ON-ENGINE FUEL PUMP ADJUSTMENT (Contd)
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
c. Recheck idle speed and
readjust as necessary.
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,
Under no circumstances should
speed setting, smoke, coolant
specifications be exceeded.
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