Isuzu engine 4j series. Manual - part 69

6C - 20  ENGINE FUEL

Pre-lift confirmation

1.  With the needle valve at full lift, release the nozzle

tester handle.

Note:

The in-line pressure will decrease and needle
valve lift (as indicated on the dial gauge) will also
decrease a little.

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

).

Note:
This point can be found while the pressure is
decreasing.

3. Confirm that pre-lift ‘liter’ is as specified.
Pre-lift

mm

                                                                                                                   

0.04

                                                                                                                   

4. If pre-lift is not as specified, replace the pins, lift piece,

spacer and nozzle assembly as a set with the service
kit.

Service kit:

                                                                                                                   

8-9720-3470-1

                                                                                                                   

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ENGINE FUEL  6C - 21

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

) so that the nozzle’s needle valve moves

through its full lift.

2. Release the nozzle tester handle so that in-line

pressure decreases.
Note:

The in-line pressure will decrease and needle
valve lift (as indicated on the dial gauge) will also
decrease a little.

3. Then, read the pressure gauge indication (second

nozzle opening pressure) the instant that the dial
gauge indicates the specified needle valve lift (usually
pre-lift liter

 

+ 0.05 mm).

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6C - 22  ENGINE FUEL

Second nozzle opening pressure adjustment
If the second nozzle opening pressure is not as specified,
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
second opening pressure must be adjusted when
the first opening pressure changes.

•

Use a micrometer to measure shim thickness.

•

Second nozzle opening pressure adjusting shims

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

Final inspection
1. Remove the dial gauge, nut and dial gauge holder.

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)

4. Set the nozzle holder to the nozzle tester and check

first nozzle opening pressure, spray condition, 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 service
kit.

CAUTION:

Pre-lift will not be as specified if only the nozzle is
replaced.

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ENGINE FUEL  6C - 23

DISASSEMBLY (4JBI/4JB1T Engine)

1. Retaining Nut

2. Injection Nozzle

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 combinations
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

4. Spring Seat

5. Spring

6. Adjusting Shim

7. Nozzle Holder

INSPECTION AND REPAIR (4JB1/4JB1 T
Engine)

Make the necessary adjustments, repairs, and part
replacements if excessive wear or damage is discovered
during inspection.

Inspection Nozzle Needle Inspection

1. Remove the needle from the nozzle body.
2. Carefully wash the nozzle needle and the nozzle body

in clean diesel fuel.

3. Check that the nozzle needle moves smoothly inside

the injection nozzle body.
If the nozzle needle does not move smoothly, it must
be repaired (See "Nozzle Lapping Procedure" belows).

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