resting on the ends of exhaust valve when
t i g h t e n i n g rocker shaft bracket bolts. Note
position of exhaust valve bridge before,
during, and after tightening the rocker shaft
(d) Move rocker arm assembly into position and
t i g h t e n rocker arm bracket bolts to 50-55 lb-ft. of
Do not bend fuel pipes and do not exceed
specified torque. Excessive torque will twist
or fracture flared end of fuel line and result
in leaks. Lubricating oil diluted by fuel oil can
cause serious damage to engine bearings.
(e) Tighten the fuel pipe connections to 12-15
lb-ft. of torque.
(f) Adjust the exhaust valves (para 3-12, b).
(g) Time the fuel injectors (para 3-12, c).
(h) Install the rocker arm cover (para 3-16).
i. Checking Spray Tip Concentricity.
(1) Place the injector in the concentricity gage as
illustrated in figure 3-51 and adjust the dial indicator
(2) Rotate the injector 360° and note the total
runout as indicated on the dial.
(3) If the total runout exceeds 0.008 inch, remove
the injector from the gage. Loosen the injector nut, re-
center the spray tip, tighten the nut to 75-80 lb ft.
torque and recheck the concentricity.
(4) If after several attempts, the spray tip cannot
be positioned satisfactorily, check the reassembly of
(b) Connect a flexible tube to the fuel return line
the entire injector.
as illustrated in figure 3-53.
3-19. Fuel Pump
(c) Start and run engine at approximately 1200
a. General The fuel pump is a positive displacement
(d) Collect the fuel from the return line for a pe-
gear type which transfers the fuel from the supply
riod of one minute.
tank to the fuel injectors. The pump circulates an ex-
(e) Stop the engine and measure the fuel col-
cess supply of fuel through the injectors which purges
lected. The volume of fuel collected must be not less
the air from the system and cools the injectors. The un-
than 1/2 gallon.
used portion of fuel returns to the fuel tank by means
(f) If fuel flow is insufficient for satisfactory
of a fuel manifold and return line.
engine performance, clean or replace fuel strainer.
(g) If fuel flow is still insufficient, replace sec-
(1) Fuel Pressure Test.
ondary fuel filter and recheck fuel flow. If fuel flow is
(a) Remove rocker arm cover (para 3-16).
unsatisfactory, replace fuel pump.
(b) Connect a pressure gage as illustrated in fig-
(h) Remove flexible hose and reconnect return
line to fuel supply tank.
(c) Start and run engine at 2500 RPM.
(d) Observe fuel pressure on pressure gage. The
(1) Remove the fuel pump (TM 10-3930-634-12).
pressure must be not less than 35 psi. Nominal fuel
(2) Cap fuel lines.
pressure at 2500 RPM is 45-70 psi.
(e) If pressure is below 35 psi repair the fuel sys-
(1) Disassemble the fuel pump in numerical se-
quence as shown in figure 3-54.
(f) Remove gage, replace fuel pipe and install
(2) Remove seals (13 and 14, fig. 3-54) as shown
rocker arm cover.
in figure 3-55.
(2) Fuel Flow Test.
e. Cleaning. Clean all parts with cleaning solvent
(a) Disconnect the fuel return line from the fuel
P-D-680 and blow dry with compressed air.