Isuzu N-Series. Manual — part 387
6C-26 FUEL SYSTEM
Caution:
• Secure the dial gauge so that a stroke of 2 mm
(0.08 in) can be measured.
• Do not over-tighten the nut as the dial gauge shaft
may jam. (Confirm from the dial gauge that the
shaft moves smoothly.)
6. Set the nozzle holder (1) to the nozzle tester (2)
and put needle to zero on the dial gauge.
7. Operate the nozzle tester to bleed any air from in-
side the retaining nut and to confirm that no fuel
leaks.
8. Operate the nozzle tester and increase the in-line
pressure to 34.3 — 44.1 MPa (350 — 450 kg/cm
2
/ 4,975 — 6,396 psi) so that the nozzle’s needle
valve moves through its full lift.
Record full lift ‘L’. (Read dial gauge)
Notice:
The above operation is used to determine whether the
nozzle seat is worn and whether the nozzle assembly is
in good condition.
Legend
1. Dial gauge
2. Nut
3. Holder
4. Pin
5. Nozzle holder
6. First spring seat
N6A0873E
Nozzle Full Lift
mm (in)
0.30 (0.0118)
Legend
1. Needle valve
2. First nozzle opening pressure 34.3 — 44.1
MPa (350 — 450 kg/cm
2
/ 4,975 — 6,396 psi)
3. In line pressure
N6A0867E
N6A0875E
FUEL SYSTEM 6C-27
Pre-lift Confirmation
1. With the needle valve at full lift, release the nozzle
tester handle.
Notice:
The in-line 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 ‘l’ from the dial gauge in-
dication (once the needle valve has descended
when the second spring has stopped operating).
Refer to the pre-lift measuring point for ‘l’.
Pre-lift measuring point:
Read the dial gauge at first nozzle opening pressure
+approx 1 MPa (10 kg/cm
2
/ 145 psi).
Notice:
This point can be found while the pressure is decreas-
ing.
3. Confirm that pre-lift ‘l’ is as specified.
Legend
1. Pressure gauge
Legend
1. Needle valve lift
2. In line pressure
N6A0876E
N6A1650E
Pre-lift
Engine
Pressure MPa (kg/cm
2
/
psi)
Lift mm (in)
4HG1-T
19.1 (195/2,770)
0.04 (0.0016)
Legend
1. Needle valve lift
2. Measuring point of prelift
3. First nozzle opening pressure
N6A0878E
N6A0879E
6C-28 FUEL SYSTEM
4. If pre-lift is not as specified, replace the pins, lift
piece, spacer and nozzle assembly as a set with
the service kit.
Second Nozzle Opening Pressure Confirmation
1. After pre-lift confirmation, operate the nozzle tester
to increase in-line pressure to 34.3 — 44.1 MPa
(350 — 450 kg/cm
2
/ 4,975 — 6,396 psi) so that the
nozzle’s needle valve moves through its full lift.
2. Release the nozzle tester handle so that in-line
pressure decreases.
Notice:
The in-line 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
Legend
1. Push rod
2. Spring seat
3. Spacer
4. Second spring
5. Adjusting shim
6. Lift piece
7. Needle valve
Service kit:
4HG1-T
897313-8970
Legend
1. Lift piece
2. Nozzle assembly
3. Pin
4. Spacer
5. Capsule
N6A0880E
Legend
1. Nozzle holder
2. Nozzle tester
Legend
1. Needle valve lift
2. Second nozzle opening pressure 34.3 — 44.1
MPa (350 — 450 kg/cm
2
/ 4,975 — 6,396 psi)
3. In line pressure
N6A0867E
N6A1651E
FUEL SYSTEM 6C-29
gauge indicates the specified needle valve lift (usu-
ally pre-lift l + 0.05 mm (0.0020 in).
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.
• Use some combination of 3 adjusting shims to ad-
just the pressure.
• Second nozzle opening pressure adjusting shims
Second Nozzle Opening Pressure
Lift mm (in)
Pressure MPa (kg/cm
2
/psi)
4HG1-T
0.09
(0.0035)
22.1 — 23.0 (225 — 235/
3,200 — 3,342)
Legend
1. When needle valve lift is l + 0.05 mm (0.0020
in)
2. Dial gauge
3. Full needle valve lift
Part No. (ISUZU)
Thickness mm (in)
897116-0290
0.10 (0.0039)
897116-0320
0.20 (0.0079)
897116-0330
0.30 (0.0118)
897116-0340
0.40 (0.0157)
897116-0350
0.50 (0.0197)
897116-0360
0.51 (0.0201)
N6A0883E
897116-0370
0.52 (0.0205)
897116-0380
0.53 (0.0209)
897116-0390
0.54 (0.0213)
897116-0400
0.55 (0.0217)
897116-0410
0.56 (0.0220)
897116-0420
0.57 (0.0224)
897116-0430
0.58 (0.0228)
897116-0440
0.59 (0.0232)
Legend
1. Second nozzle opening pressure adjusting
shim
2. Second spring
3. Collar
4. Push rod
5. Spring seat
Part No. (ISUZU)
Thickness mm (in)
N6A0862E
N6A1652E
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