Isuzu N-Series. Manual - part 309

00-48 SERVICE INFORMATION

Fan Belt

Check the drive belt tension.
Depress the drive belt mid-portion with a 98 N (10 kg/22
lb) force.

Check the drive belt for cracking and other damage.

• Crankshaft damper pulley
• Generator pulley
• Cooling fan pulley

Fan Belt Adjustment
Fan belt tension is adjusted by moving the generator.

Tighten:
Bolt 1 to 40 N

⋅m (4.1 kg⋅m/30 lb⋅ft)

Bolt 2 to 24 N

⋅m (2.4 kg⋅m/17 lb⋅ft)

Bolt 3 to 46 N

⋅m (4.7 kg⋅m/34 lb⋅ft)

If equipped with A/C compressor, loosen the A/C drive
belt tension pulley adjust bolt and lock nut. Then free the
A/C drive belt. When finishing the fan belt adjustment,
adjust the A/C drive belt and check the belt tension.

Air Conditioning (A/C) Compressor Drive Belt

Check the drive belt tension.

• Depress the drive belt mid-portion with a 98 N (10

kg/22 lb) force.

Check the drive belt for cracking and other damage.
A/C compressor drive belt tension is adjusted by moving 
the tension pulley.
When finishing the fan drive belt, then adjust the A/C
drive belt.

Tighten:
Locking nut to 27 N

⋅m (2.8 kg⋅m/20 lb⋅ft) 

Legend

1. Thermometer
2. Aditating rod
3. Wooden piece
4. Thermostat
5. Heat

Drive Belt Deflection

mm (in)

8 — 12 (0.31 — 0.47) ... New belt

10 — 14 (0.39 — 0.55) ... Reuse belt

N6A0037E

Drive Belt Deflection

mm (in)

16 — 20 (0.63 — 0.79) ... New belt

18 — 22 (0.71 — 0.87) ... Reuse belt

N6A0038E

N6A0039E

SERVICE INFORMATION 00-49

Engine Control

Idling Speed Inspection

1. Set the vehicle parking brake and chock the drive

wheels.

2. Place the transmission in neutral.
3. Start the engine and allow it to warm up.
4. Check that the idling control knob is in the engine

idling position.

5. Set a tachometer to the engine.
6. Check the engine idling speed.

Engine idling speed should be as below.

If the engine idling speed is outside the specified
range, it must be adjusted.

Idling Speed Adjustment

1. Loosen the idling set bolt lock nut on the injection

pump.

2. Adjust the idling speed with the idling set bolt.
3. Tighten the lock nut.

Idling Speed Check & Adjustment (4HF1-2 mod-
el only)

1. Warm up the engine.
2. Measure idling speed by means of tachometer.
3. If idling speed is out of the standard, adjust with an

idling adjust bolt (indicated by an arrow mark).
Idling speed: 575 — 625 rpm

Accelerator Control

Accelerator Control Cable Adjustment

1. Loosen the accelerator cable clamp bolt (1).
2. Check that the idling control knob is in the engine

idling position.

3. Hold the accelerator lever (2) in the fully closed po-

sition and stretch the control cable (3) in the direc-
tion indicated by the arrow to remove any slack.

Legend

1. A/C compressor pulley
2. Tension pulley
3. Generator pulley
4. Crankshaft damper pulley
5. Tension pulley lock nut

Engine Idling Speed

rpm

4HF1

M/T

550 — 625

4HF1-2

M/T

575 — 625

4HG1

M/T

550 — 600

4HG1-T

M/T

600 — 650

4HE1-TC 

(4HE1-TC-XS, 

XN) 98EPA

M/T

775 — 825

4HE1-TC 

(4HE1-TC-XS, 

XN) SPEC. 

EURO3

M/T

775 — 825

N6A0040E

N6A0041E

00-50 SERVICE INFORMATION

Engine Stop Control

Adjustment

1. Check that the key switch is either in the “LOCK”

position or removed from the engine.

2. Loosen the bolt (1).
3. Pull the fuel cut lever (2) as far as possible and hold

it.

4. Remove cable slackness (A) by pulling the cable in

the direction of the arrow in the illustration.

5. Tighten the bolt (1).

Accelerator Pedal Adjustment

1. Press the accelerator pedal to the floorboard and

hold it.

2. Use the stopper bolt (2) to adjust the clearance be-

tween the stopper bolt end and the accelerator
pedal (3) lower face.

Valve Clearance Adjustment

1. Bring the piston in either the No.1 cylinder or the

No.4 cylinder to TDC on the compression stroke by
turning the crankshaft until the crankshaft damper
pulley timing mark is aligned with the TDC notched
line.

Notice:
If there are two marks on the crank pulley, the front side
of mark is for setting BTDC 49

° and the rear side of mark

is for setting TDC.

2. Tighten the rocker arm shaft bracket nuts and bolts

to the specified torque in numerical order a little at
a time as shown in the illustration.

Accelerator Pedal Clearance

mm (in)

0 — 2 (0 — 0.079)

N6A1614E

N6A0043E

Legend

1. Full stroke 0 — 2 mm (0 — 0.079 in)
2. Stopper bolt
3. Accelerator pedal

N6A0044E

N6A0045E

SERVICE INFORMATION 00-51

Tighten:
Rocker arm shaft bracket nut and bolt to

• Nut (A) 27 N

⋅m (2.8 kg⋅m/20 lb⋅ft)

• Bolt (B) 56 N

⋅m (5.7 kg⋅m/41 lb⋅ft)

• Bolt (C) 27 N

⋅m (2.8 kg⋅m/20 lb⋅ft)

• Apply engine oil to the threaded portion of the

nuts marked with “A” and the bolts with
“B”shown in the illustration, and then tighten
them to the specified torque.

3. Check for play in the No.1 intake and exhaust valve

rocker arms.
If the No.1 cylinder intake and exhaust valve rocker
arms have play, the No.1 piston is at TDC on the
compression stroke.
If the No.1 cylinder intake and exhaust valve rocker
arms are depressed, the No.4 piston is at TDC on
the compression stroke.

Adjust the No.1 or the No.4 cylinder valve clear-
ance while their respective cylinders are at TDC on
the compression stroke.

4. Loosen each valve clearance adjusting screw as

shown in the illustration.

5. Insert a feeler gauge of the appropriate thickness

between the rocker arm and the valve stem end.

6. Turn the valve clearance adjusting screw until a

slight drag can be felt on the feeler gauge.

7. Tighten the lock nut securely.
8. Rotate the crankshaft 360 degrees.
9. Realign the crankshaft damper pulley timing mark

with the TDC notched line.

10. Adjust the clearance for the remaining valves as

shown in the illustration.

N6A0046E

N6A0047E

Valve Clearance

mm (in)

At cold

0.40 (0.016)

N6A0048E

N6A0049E