Isuzu N-Series. Manual — part 614
6C-26 ENGINE FUEL
Notice:
The inline pressure will decrease and needle valve lift
(as indicated on the dial gauge) will also decrease a lit-
tle.
2. Read the needle valve lift ‘liter’ from the dial gauge
indication (once the needle valve has descended
when the second spring has stopped operating).
Refer to the pre-lift measuring point for ‘liter’.
Pre-Lift Measuring Point:
Read the dial gauge at first nozzle opening pressure
+approx 1 MPa (10 kg/cm
2
).
Notice:
This point can be found while the pressure is decreas-
ing.
3. Confirm that pre-lift ‘liter’ is as specified.
4. If pre-lift is not specified, replace the pins, lift piece,
spacer and nozzle assembly with the service kit.
Service kit:
8-9720-3470-1
Legend
A. Inline pressure
1. Needle valve lift
N6A3421E
N6A3422E
Legend
A. Inline pressure
1. Needle valve lift
2. First nozzle opening pressure
3. Measuring point of pre-lift
Pre-lift
mm (in)
0.04 (0.002)
Legend
1. Push rod
2. Spring seat
3. Spacer
4. Second spring
5. Adjusting shim
6. Lift piece
7. Needle valve
N6A3423E
ENGINE FUEL 6C-27
Second Nozzle Opening Pressure Confirmation
1. After pre-lift confirmation, operate the nozzle tester
to increase inline pressure to 34.3 — 44.1 MPa
(350 — 450 kg/cm
2
) so that the nozzle’s needle
valve moves through its full lift.
2. Release the nozzle tester handle so that inline
pressure decreases.
Notice:
The inline pressure will decrease and needle valve lift
(as indicated on the dial gauge) will also decrease a lit-
tle.
3. Then, read the pressure gauge indication (second
nozzle opening pressure) the instant that the dial
gauge indicates the specified needle valve lift (usu-
ally pre-lift liter + 0.05 mm).
Legend
1. Lift piece
2. Nozzle assembly
3. Pin
4. Spacer
5. Capsule
Legend
1. Nozzle holder
2. Nozzle tester
N6A3424E
N6A3411E
Legend
A. Inline pressure
1. Needle
2. Second nozzle opening pressure
Legend
1. When needle valve lift is L + 0.05 mm
2. Full needle valve lift
3. Dial gauge
N6A3794E
N6A3425E
6C-28 ENGINE FUEL
Second Nozzle Opening Pressure Adjustment
If the second nozzle opening pressure is not as speci-
fied, disassemble the nozzle from the nozzle holder and
replace the shim until the pressure is as specified.
Caution:
• Because the second opening pressure changes
when the first opening pressure changes, the sec-
ond opening pressure must be adjusted when the
first opening pressure changes.
• Use a micrometer to measure shim thickness.
• Second nozzle opening pressure adjusting shims
Final Inspection
1. Remove the dial gauge (1), nut (2) and dial gauge
holder (3).
Legend
1. Pressure gauge
N6A3795E
N6A3406E
Legend
1. Second nozzle opening pressure adjusting
shim
2. Second spring
3. Collar
4. Push rod
5. Spring seat
Part No.
Thickness (mm)
8-9711-6034-0
0.40
8-9711-6035-0
0.50
8-9711-6037-0
0.52
8-9711-6039-0
0.54
8-9711-6041-0
0.56
8-9711-6043-0
0.58
8-9711-6044-0
0.59
N6A3412E
ENGINE FUEL 6C-29
2. Remove the adjustment retaining nut and gasket.
3. Install the original retaining nut, confirm that the
pins are inserted fully into the nozzle, and then
hand-tighten the retaining nut. Then, tighten the
original retaining nut to the specified torque.
Torque: 59 — 79 N
⋅m (6.0 — 8.0 kg⋅m/43.5 — 58.2
lb
⋅ft)
4. Set the nozzle holder to the nozzle tester and
check first nozzle opening pressure, spray condi-
tion, seat oil tightness and each part for oil leaks.
5. When replacing the nozzle, replace the nozzle, lift
piece, pins and spacer as a set with the nozzle ser-
vice kit.
Caution:
Pre-lift will not be as specified if only the nozzle is re-
placed.
Disassembly (4JB1 Engine)
1. Retaining Nut (1)
2. Injection Nozzle (2)
1) Remove the nozzle assemblies from the nozzle
holders.
Tag the nozzle assemblies and the nozzle
holders to ensure that they are reinstalled in
their original positions.
The nozzle assembly and nozzle holder combi-
nations must not be interchanged.
2) Immerse the injection nozzle in a tool tray filled
with clean diesel oil to protect them from dust.
3. Spacer (3)
4. Spring Seat (4)
5. Spring (5)
6. Adjusting Shim (6)
7. Nozzle Holder (7)
Legend
1. Torque wrench
2. Retaining nut (Special tool)
N6A3426E
N6A3410E
Legend
1. Nozzle holder
2. Nozzle tester
N6A3411E
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