Opening Pressure Test

TM 5-2420-224-34

FUEL INJECTOR NOZZLE TEST AND REPAIR (CONT)

Opening Pressure Test

Work pump lever slowly until nozzle begins to spray; read opening pressure. Opening pressure should

read 2610 psi (180 bar).

If opening pressure is too high or too low, disassemble, clean, and adjust injector nozzle.

NOTE

To lower pressure, use thinner washers. To raise pressure, use thicker washers. Use no

more than two washers in any injector nozzle. If more than two washers are needed,

replace pressure spring.

If necessary, replace injector nozzle.

Leak Test

Work pump Iever slowly until pressure gage reads 2320 psi (160 bar). Nozzle does not leak if drops

do not appear at nozzle mouth within 10 seconds. If injector nozzle leaks, disassemble and clean.

CAUTION

I n c r e a s e pressure slowly and release pressure slowly, to avoid damaging test

set.

If nozzle still leaks after cleaning nozzle body and needle, replace both nozzle body and needle.

Spray Pattern and Chatter Behavior

Spray Pattern: To use test set correctly, gently depress lever several times until resistance is felt on

each stroke. Then apply one full stroke slowly and observe the spray. At very low test pressure, spray

pattern should be spread with rough atomization. in the chatterless range, spray pattern should be

tighter but anatomized. As the pressure increases, spray pattern should become complete and finely

atomized.

Chatter Behavior: Good chatter during fast and slow lever motion; short chatterless ranges can occur

in between.

If spray pattern or chatter is not as described above, disassemble, clean, and adjust injector nozzle. If

necessary, replace injector nozzle.

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