Isuzu N-Series. Manual - part 384

6C-14 FUEL SYSTEM

INJECTION NOZZLE ASSEMBLY

Component

Legend

1. Nozzle cover

3. Injection pipe

2. Leak off pipe

4. Injection nozzle assembly

N6A0839E

FUEL SYSTEM 6C-15

4HE1-TC (Engine)

Removal

Preparation

• Disconnect battery ground cable.
• Tilt the cab.

1. Nozzle Cover
2. Leak-Off Pipe
3. Fuel Injection

1) Loosen the injection pipe sleeve nuts (1).

Do not apply excessive force to the injection
pipes (4).

2) Loosen the injection pipes clips (2).
3) Remove the injection pipe assembly.

Plug the delivery valve holder ports and nozzle
holder (3) ports with caps to prevent the entry
of foreign material.

Legend

1. Nozzle cover

3. Injection pipe

2. Leak off pipe

4. Injection nozzle assembly

N6A0840E

6C-16 FUEL SYSTEM

4. Injection Nozzle Assembly

Mark the nozzle holder assemblies fitting positions
by tagging each nozzle holder assembly with the
cylinder number from which it was removed.

Inspection

Before disassembling the injection nozzle assembly,
check nozzle opening pressure, spray pattern, chatter
and oil leakage.
Opening Pressure
Use a nozzle tester to check the injection nozzle open-
ing pressure.
If the opening pressure is above or below the specified
value, the injection nozzle must be replaced or adjusted.

Spray Pattern
Check the spray pattern
Refer to the illustration.
Spray Condition

• Correct (1)
• Incorrect (Restrictions in orifice) (2)
• Incorrect (Dripping) (3)

If the spray condition is bad, the injection nozzle must be
replaced or adjusted.

N6A0841E

N6A0842E

Injection Nozzle Opening 
Pressure

MPa (kg/cm

2

/psi)

4HF1/4HF1-2/4HG1

18.1 (185/2,631)

4HE1-TC

21.6 (220/3,128)

4HG1-T

1st

18.1 (185/2,631)

2nd

21.1 (215/3,057)

N6A0843E

N6A0029E

FUEL SYSTEM 6C-17

Leakage
Hold the tester handle to about 2,070 kPa (21 kg/cm

2

/

300 psi) below the opening pressure. If no drops of fuel
fall from the nozzle tip within 10 seconds, the nozzle is
not leaking.
Chatter
An easily audible chatter at all pump lever speeds
should be heard.

Warning:

WARNING:
TEST FLUID FROM THE INJECTION NOZZLE WILL
SPRAY OUT UNDER GREAT PRESSURE. IT CAN
EASILY PUNCTURE A PERSON’S SKIN. KEEP
YOUR HANDS AWAY FROM THE INJECTION NOZ-
ZLE TESTER AT ALL TIMES.

Disassembly

Clamp the injection nozzle holder in a vice.

1. Flange
2. Retaining Nut

Use a wrench to remove the injection nozzle retain-
er nut.

3. Injection Nozzle

Keep the nozzle along with the needle valve sepa-
rately to maintain the original nozzle to needle
valve combination.

4. Spacer
5. Spring Seat
6. Nozzle Spring
7. Adjusting Shim

Keep the adjusting shims in the original groups to
hold the initial shim to nozzle spring combination.

8. Nozzle Holder Body

Caution:

• Wash all the parts removed and arrange them on a

cylinder basis, care should be taken not to miss
any parts.

• Soak the nozzle assembly in a parts receptacle

filled with light oil.

• Care should be taken not to miss shim, if used.

Legend

1. Flange
2. Retaining nut
3. Injection nozzle
4. Spacer
5. Spring seat
6. Nozzle spring
7. Adjusting shim
8. Nozzle holder body

N6A0845E

N6A0846E

N6A0847E