TM 5-3810-300-24&P-3
Fuel Injector
2.1.1
the spray tip and needle valve assembly should be
replaced.
5. Reassemble the injector as outlined under Assemble
Injector and check the injector output with calibrator J
22410.
Needle Valve Tip Test (Using Auxiliary Tester J
22640)
1. Connect the pipe from auxiliary tester J 22640 to the
rear of the J 23010 tester at the connection located near
the bottom of the tester (Fig.17).
2. Assemble cleaned injector parts, including the check
valve cage, spring, spring seat, spring cage and spray tip
assembly, on the auxiliary tester J 22640 (Fig. 18).
3. Carefully pilot the injector nut over the spray tip and
Fig. 16 - Checking Needle Valve Lift
valve parts and thread it on the auxiliary tester.
4. Tighten the injector nut.
a. Actuate pump lever I several times and hold the
5. Open the valve on the auxiliary tester and place lever
pressure at 1500 psi for 15 seconds.
4 in the up (horizontal) position.
6. Install the shield on the auxiliary tester and operate
b. Inspect the spray tip for leakage. There should
pump lever I until the needle' valve has opened several
be no fuel droplets, although a slight wetting at
times to purge the air from the system.
the spray tip is permissible.
7. Operate pump lever I with smooth, even strokes and
note the pressure on gage I when the needle valve
Needle Valve Lift Test
opens. The valve should open between 2300 and 3300
psi. The opening and closing action should be sharp and
To measure the needle valve lift, use tool J 9462-01 (Fig.
produce a finely atomized spray.
16) as follows:
If the valve opening pressure is below 2300 psi and/or
1. Zero the indicator by placing the bottom surface of the
atomization is poor, the cause is usually a weak valve
plunger assembly on a flat surface and zero the indicator
spring or poor needle valve seat.
dial.
If the valve opening pressure is within 2300-3300 psi,
2. Place the spray tip and needle valve assembly tight
proceed to check for spray tip leakage as follows:
against the bottom of the gage with the quill of the needle
valve in the hole in the plunger.
a. Actuate the pump lever several times and hold
the pressure at 1500 psi for 15 seconds.
3.
While holding the spray tip and needle valve
assembly tight against the gage, read the needle valve
b. Inspect the spray tip for leakage. There should
lift on the indicator. The lift should be .008" to .018" .
be no fuel droplets although a slight wetting at
the spray tip is permissible.
If it exceeds .018", the tip assembly must be replaced.
Perform the needle valve lift test.
If it is less than .008", inspect for foreign material
between the needle valve and the tip seat.
Fuel Output Test
4. If the needle valve lift is within limits, install a new
Perform the injector fuel output test in calibrator J 22410.
needle valve spring and recheck the valve opening
pressure and valve action. Low valve opening pressure
When injectors are removed from an engine for fuel
or poor atomization with a new spring and seat indicates
output testing and, if satisfactory, reinstalled without
disassembly, extreme care should be taken to avoid
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