Isuzu N-Series. Manual - part 615

6C-30 ENGINE FUEL

Inspection and Repair (4JB1 Engine)

Make the necessary adjustments, repairs, and part re-
placements 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 in-

side the injection nozzle body.
If the nozzle needle does not move smoothly, it
must be repaired (See “Nozzle Lapping Proce-
dure”).

Nozzle Lapping Procedure

1. Lap the nozzle needle (1) and the nozzle body (2)

by applying a compound of oxidized chrome and
animal oil (3).

Notice:
Do not apply an excessive amount of the oxidized
chrome and animal oil compound to the injection needle
valve seat area. Applying too much compound will
cause the injection nozzle needle and the injection noz-
zle body cavity to wear excessively.

2. Carefully wash the needle valve and the nozzle

body in clean diesel fuel after lapping.

Nozzle Body and Needle Valve Inspection
Check the nozzle body and the needle valve for damage
and deformation.
The nozzle and body assembly must be replaced if ei-
ther of these two conditions are discovered during in-
spection.

N6A3430E

N6A3431E

N6A3431E

N6A3432E

ENGINE FUEL 6C-31

Reassembly

1. Nozzle Holder
2. Adjusting Shim
3. Spring
4. Spring Seat
5. Spacer
6. Injection Nozzle
7. Retaining Nut

Tighten:
Retaining nut to 34 N

⋅m (3.5 kg⋅m/25 lb⋅ft)

Injection Nozzle Adjustment

1. Attach the injection nozzle holder to the injection

nozzle tester.

2. Apply pressure to the nozzle tester to check that

the injection nozzle opens at the specified pres-
sure.

If the injection nozzle does not open at the specified
pressure, install or remove the appropriate number of
adjusting shims to adjust it.

Removing or installing one shim will increase or de-
crease the nozzle opening pressure approximately
369.46 kPa (3.77 kg/cm

2

 /53.6 psi).

Warning:

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

Installation (4JB1/4JH1-TC Engine)

1. Injection Nozzle

1) Install the injection nozzle gasket (1) and the O-

ring (2) to the injection nozzle holder (3).
Be sure that the O-ring fits snugly in the injec-
tion nozzle groove.

2) Apply engine oil to the cylinder head nozzle

holder hole.

3) Install the nozzle holder together with the noz-

zle holder bracket (4) to the cylinder head.

Tighten:
37 N

⋅m (3.8 kg⋅m/27 lb⋅ft)

N6A3433E

N6A3434E

kPa (kg/cm

2

 /psi)

18,142 (185/2630)

Adjusting Shim Availability

mm (in)

Range

0.50 — 1.50 (0.02 — 

0.06)

Increment

0.025 (0.001)

Total number of Shims

40

N6A3435E

6C-32 ENGINE FUEL

2. Leak Off Hose
3. Injection Pipe

Legend

A. 4JH1-TC

N6A3436E

N6A3437E

ENGINE FUEL 6C-33

INJECTION PUMP ASSEMBLY (4JB1/4JG2, Gear Drive Type)

Component

4JB1/4JG2

Legend

1. Cooling fan assembly

8. Air intake duct

2. Fan Shroud

9. Injection pump control cable

3. Power steering pump drive belt

10. Fuel hose

4. A/C compressor drive belt

11. CSD water hose

5. AC generator drive belt

12. Injection pump harness

6. Noise shield cover

13. Injection pipe

7. Noise cover spacer

14. Injection pump assembly

N6A3438E