Isuzu N-Series. Manual - part 308

00-44 SERVICE INFORMATION

3. Apply a thin coat of engine oil to the O-rings.

4. Install the filter assemblies.

Carefully turn each assembly clockwise until the O-
ring is fitted against the filter cover sealing face.

5. Use the filter wrench to turn in each filter assembly

an additional 1/3 to 2/3 of turn.

6. Operate the priming pump on the fuel filter to bleed

the fuel system.
Refer to “AIR BLEEDING” for more detailed infor-
mation.

Pre-fuel Filter Water Draining Procedure

The indicator light will come on when the water level in
the water separator exceeds the specified level.
Drain the water and foreign material from the water sep-
arator with the following procedure.

1. Place the end of a vinyl hose (beneath the drain

plug) in a container.

2. Loosen the air intake plug and drain plug, then

drain water.

3. After draining, securely tighten the drain plug and

air intake plug.

4. Then, operate the priming pump on the injection

pump to bleed the fuel system.

5. After starting the engine, check to see that no fuel

leaks from the drain plug.

Injection Nozzle

Pressure and Spray Condition Check

1. Use a nozzle tester to check the injection nozzle

opening pressure.
If the opening pressure is above or below the spec-
ified value, the injection nozzle must be replaced or
adjusted.
Refer to “Adjustment.”

N6A0024E

N6A0014E

N6A0026E

N6A0027E

SERVICE INFORMATION 00-45

2. Check the spray condition.

Refer to the illustration.
Spray Condition 

1) Correct
2) Incorrect (Restrictions in orifice)
3) Incorrect (Dripping)
If the spray condition is bad, the injection nozzle
must be replaced or adjusted.
Refer to “6C FUEL SYSTEM”.

Adjustment

1. Clamp the injection nozzle holder (1) in a vise (2).
2. Use a wrench to remove the injection nozzle retain-

ing nut (3).

3. Remove the injection nozzle holder from the vise.
4. Remove the injection nozzle (4), the spacer (5), the

spring seat (6) the spring (7) and the adjusting
shim (8).

5. Install the new adjusting shim, the spring, the

spring seat, the spacer, the injection nozzle, and
the retaining nut.

6. Clamp the injection nozzle holder in the vise.
7. Tighten the injection nozzle holder retaining nut to

the specified torque.

Tighten:
Injection nozzle holder retaining nut to 34 N

⋅m (3.5 kg⋅m/

25 lb

⋅ft)

8. Remove the injection nozzle holder from the vise.

Injection Nozzle Opening Pressure

Mpa (kg/cm

2

/psi)

4HF1/4HF1-2/4HG1

18.14 (185/2,631)

4HE1-TC

21.57 (220/3,128)

4HG1-T 

1st: 18.1 (185/2,631)

2nd: 21.1 (215/3,057)

N6A0028E

N6A0029E

N6A0030E

N6A0031E

00-46 SERVICE INFORMATION

9. Attach the injection nozzle holder to the injection

nozzle tester.

10. 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 speci-
fied pressure, install or remove the appropriate
number or adjusting shims to adjust it.
Removing or installing one shim will increase or
decrease the nozzle opening pressure approxi-
mately 370 kPa (3.77 kg/cm

2

 / 53.6 psi).

Air Bleeding (Except 4HF1-2 model only)
Above works refer to “FUEL SYSTEM” in this section.
Air Bleeding (4HF1-2 model only)

1. Actuate the priming pump (1) to send the air in the

fuel system to the injection pump.

2. Loosen the sedimenter air bleeding plug (2) and

operate the priming pump until no bubbles appear.

3. Tighten the air bleeding plug (2) completely.

4. Try to start the engine. If the engine is not started

within 10 seconds, air bleeding should be conduct-
ed once again.

5. Check that there is no fuel leak, and then tighten

the priming pump completely.

Water Drain
If more water than specified has collected, the warning
light is lit. Under this condition, follow the following water
drain procedure:

1. Place a container (Approximately 0.2 liters capaci-

ty) beneath the drain plug on the separator.

2. Loosen the drain plug and air bleeding plug.
3. After draining, tighten the drain plug.

4. Operate the priming pump several times again and

check for fuel leak.

5. Tighten the air bleeding plug.
6. Make sure that the warning light in the instrument

panel is off. (Except 4HE1-TC model)

Cooling System

Coolant Level

Check the coolant level and replenish the radiator re-
serve tank if necessary.
If the coolant level falls below the “MIN” line, carefully
check the cooling system for leakage. Then add enough 
coolant to bring the level up to the “MAX” line.

Notice:
Do not overfill the reserve tank.
Remove the radiator filler cap only when absolutely nec-
essary.
Always check the coolant level when the engine is cold.
Always refer to the chart at the left to determine the cor-
rect cooling water to antifreeze solution mixing 
ratio.

Adjust Shim Arailability

mm (in)

Range

0.5 — 1.5 (0.02 — 0.06)

Increment

0.025 (0.001)

Total Number of Shims

41

N6A0032E

N6A0033E

SERVICE INFORMATION 00-47

Cooling System Leakage Inspection

Clog up the reserver tank hose carefully and check the
cooling system for leakage with a radiator cap tester by
applying an air pressure of 196 kPa (2 kg/cm

2

/28 psi)

from filler neck to inside the radiator.
As the radiator upper tank is provided with a valve, the
pressure fails to rise higher than the valve opening pres-
sure unless the hose is clogged up.

Radiator Valve Inspection

Apply air pressure from filler neck using radiator cap
tester and check the opening pressure of radiator valve.
If the valve opening pressure is out of the standard value
range, replace with a new radiator valve.

Remove the radiator valve and check a negative pres-
sure valve as the center of the valve seat side. If the
negative pressure valve does not work smoothly, clean
or replace the radiator valve.

Tighten:
Radiator valve fixing to 6 N

⋅m (0.6 kg⋅m/4 lb⋅ft)

Conduct cooling system leakage check after reinstalling
the radiator valve.
Thermostat Operating Test

1. Completely submerge the thermostat in water.
2. Heat the water.

Stir the water constantly to avoid direct heat being 
applied to the thermostat.

3. Check the valve initial opening temperature.

4. Check the valve lift full opening temperature.

Legend

1. Good quality ethylene glycol anti-freeze
2. Freezing point
3. Mixing ratio

N6A1613E

N6A0035E

Radiator valve opening pressure 

kPa (kg/cm

2

/psi)

93 — 123 (0.95 — 1.25/13.5 — 17.8)

Valve Initial Opening Temperature

°C (°F)

Standard

without
jiggle
valve

Primary valve

83 — 87 (181 — 189)

Secondary
valve

80 — 84 (176 — 183)

with jiggle valve

83.5 — 86.5 (182 — 188)

Valve Lift Full Opening Temperature

°C (°F)

Standard

without jiggle valve

95 (203)

with jiggle valve

100 (212)

N6A0036E