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Fuel lnjector
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TM-10-3930-634-34 Truck Lift Fork; Diesel Engine Pneumatic Tired Wheels Rough Terrain 6 000 Lb. Capacity 24 Load Center Anthony Model MIT 6-2 Manual
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Visual Inspection of Plunger
TM 10-3930-634-34
NOTE
tion and the injector tester popping handle locked in
Immediately after removal of the fuel pipes
position by means of the handle lock, operate the
from the injectors, cover the filter caps with
pump handle to build up and maintain the pressure at
1600 to 2000 psi by actuating the pump handle. Then
shipping caps to prevent dirt from entering
the injector. Also cover the fuel pipes and
inspect for leaks at the injector f ilter cap gaskets, body
connectors to prevent entry ofdirt or foreign
plugs and injector nut seal ring.
material.
NOTE
(3) Crank the engine with the starting motor to
If there is excessive clearance between the
plunger and bushing, pressure beyond the
bring the push rod ends, outer ends of the injector and
normal valve opening pressure cannot be ob
the valve rocker arms in line horizontally.
(4) Remove the rocker arm shaft bracket bolts and
tained. Replacement of the plunger and bush-
fuel injector clamp as illustrated in figure 3-31. Pivot
ing assembly is then required.
rocker arms back as shown.
(5) Remove the injector as illustrated in figure
It is normal for fuel to seep out around the
c. Fuel Injector Testing.
rack due to high pressure fuel being applied
(1) General. If inspection does not reveal any ex-
to a normally low pressure area in the injec-
tor assembly. However, fuel droplets at the
ternal damage, make a series of tests to determine the
rack indicate excessive leakage.
condition of the injector to avoid unnecessary repair.
(e) Relieve test pressure slowly to prevent dam-
An injector that passes all the tests outlined below is
age to test gage.
considered satisfactory for service. Test the fuel injec-
(4) Injector Holding Pressure Test.
tor as follows:
(a) Operate pump handle to bring pressure up to
(2) Control Rack and Plunger Movement.
(a) Place the fuel injector in a tester, with the
approximately 450 psi (fig. 3-34).
(b) Close fuel shut-off valve and note pressure
dowel in the underside of the injector located in the
proper slot or hole in the adapter plate. Position the
drop. The time for a pressure drop from 450 psi to 250
psi should be not less than 40 seconds.
handle support to proper height (fig. 3-33).
(c) If injector pressure drops from 450 psi to
CAUTION
When testing an injector just removed from
250 psi in less than 40 seconds, inspect injector for
an engine, the flow of fuel through the injec-
leaks as follows:
1. Thoroughly dry injector with compressed
tor on the tester should be the same as in the
engine. Connections on the test head of the
air.
2. Open tester fuel valve and operate the
tester may be changed to obtain the correct
direction of flow.
pump handle to maintain testing pressure (fig. 3-34).
(b) Place handle on top of injector follower then
3. Check for a leak at injector rack opening. A
leak indicates a poor bushing-to-body fit.
close inlet and outlet clamps to hold injector in tester.
4. A leak around the spray tip or seal ring usu-
With injector control rack held in the NO FUEL posi-
ally is caused by a loose injector nut, a damaged seal
tion, push handle down and depress follower to bottom
ring, or a brinelled surface on injector nut or spray tip.
of its stroke. Slowly release pressure on handle while
5. A leak at filter cap indicates a loose filter
moving control rack back and forth, as shown in figure
3-33 until the follower reaches top of its travel. If the
cap or a damaged filter cap gasket.
6. A "dribble" at spray tip orifices indicates a
rack does not move freely it indicates that internal
leaking valve assembly due to a damaged surface or
parts of the injector are misalined, damaged or dirty.
(3) High Pressure Test.
dirt.
(5) Spray Pattern Test.
(a) Install injector in test stand as shown in
CAUTION
(b) Thoroughly dry the injector with com-
To prevent damage to pressure gage, do not
pressed air.
exceed 250 psi.
(c) Check the fuel connections for leaks. If leaks
(a) After completing injector holding pressure
have occurred, tighten the connections, dry the injec-
test, open fuel shut-off valve, then place injector rack
tor and recheck.
in full-fuel position and operate injector several times
CAUTION
in succession by operating tester popping handle at ap-
Do not permit the pressure in the injector
proximately 40 strokes per minute as shown in figure
tester to equal or exceed the capacity of the
3-34. Observe the spray pattern to see that all spray
orifices are open and injecting evenly. The beginning
(d) With the injector rack in the full-fuel posi-
3-27

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