Isuzu N-Series. Manual - part 556

SERVICE INFORMATION 00-39

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

1. Crankshaft damper pulley (1)
2. Oil pump pulley (2)
3. Compressor pulley or idler pulley (3)

Engine Control

Idling Speed Inspection

1. Set the vehicle parking brake and choke the drive

wheels.

2. Place the transmission in neutral.
3. Start the engine and allow it to warm up.
4. Disconnect the engine control cable from the con-

trol lever.

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

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

Idling Speed Adjustment

(4JB1/4JB1-TC/4JG2 only)

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

pump idling set bolt.

2. Adjust the idling speed to the specified range by

turning the idling set bolt.

3. Lock the idling set bolt with the idling set bolt lock

nut.

4. Check that the idling control cable is tight (free of

slack).
If required, remove the slack from the cable.

Accelerator Control Cable Adjustment

(4JB1/4JB1-TC/4JG2 Only)

1. Loosen the accelerator cable clamp bolt.
2. Check that the idling control knob on the instru-

ment panel is in the engine idling position.

3. Hold the accelerator lever in the fully closed posi-

tion and stretch the control cable in the direction in-
dicated by the arrow to remove any slack.

Accelerator Pedal Adjustment

LHD

1. Loosen the lock nut.
2. Adjust bolt height from floor.

Belt Deflection

mm (in)

8 — 12 (0.32 — 0.47)

Engine Idling Speed

rpm

4JB1 / 4JB1-TC

750 — 790

4JG2

700 — 740

4JH1-TC

675 — 725

N6A3022E

Adjust Bolt Height (A)

mm (in)

18 — 28 (0.71 — 1.1)

N6A3779E

N6A3024E

00-40 SERVICE INFORMATION

3. Check to see if the accelerator pedal play is in the

range of 5 to 10mm above the pedal pad.

4. Press down on the accelerator pedal fully and

check to see if the engine rotates at its maximum
speed with each of the linkage in the smooth oper-
ation.

5. In the operating range of accelerator pedal and the

injection pump lever returns to their respective
original positions without fail.

RHD

1. Hold the accelerator pedal pad securely by hand,

and give it a full stroke.

2. Adjust the stopper bolt so that the clearance be-

tween the pad stopper bolt and the rear side of the
pad becomes the specified length.

3. Check to see if the accelerator pedal play is in the

range of 5 to 10mm above the pedal pad.

4. Press down on the accelerator pedal fully and

check to see if the engine rotates at its maximum
speed with each of the linkage in the smooth oper-
ation.

5. In the operating range of accelerator pedal and the

injection pump lever returns to their respective
original positions without fail.

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 TDC line is aligned with the timing
pointer.

2. Check the rocker arm shaft bracket nuts for loose-

ness.
Tighten any loose rocker arm shaft bracket nuts
before adjusting the valve clearance.

Tighten:

• Rocker arm shaft bracket nut to 54 N

⋅m (5.5 kg⋅m / 40

lb

⋅ft)

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

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

mm (in)

0 — 2 (0 — 0.079)

N6A3025E

N6A3026E

N6A3027E

SERVICE INFORMATION 00-41

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.

• No.1 Cylinder T.D.C. (Compression stroke)

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

°.

9. Realign the crankshaft damper pulley TDC

notched line with the timing pointer.

10. Adjust the clearance for the remaining valves as

shown in the illustration.

• No.4 Cylinder T.D.C. (Compression stroke)

Injection Timing Adjustment

(4JB1/4JB1-TC/4JG2 Only)

1. Check that the notched line on the injection pump

flange is aligned with the front plate or the timing
gear case notched line.

2. Bring the piston in the No. (1) cylinder to TDC 1 on

the compression stroke by turning the crankshaft
until the crankshaft pulley TDC line is aligned with
the timing mark (2).

Valve Clearance (At Cold)

mm (in)

0.4 (0.016)

N6A3028E

N6A3029E

N6A3030E

N6A3031E

00-42 SERVICE INFORMATION

Notice:
Check for play in the No. 1 intake and exhaust valve
push rods.
If the No. 1 cylinder intake and exhaust valve push rods
have play, the No. 1 piston is at TDC on the compres-
sion stroke.

3. Disconnect the injection pipe from the injection

pump.

4. Remove one bolt from the distributor head.
5. Insert a screwdriver into a hole in the fast idle lever

and turn the lever to release the W-C.S.D. function.
(If so equipped)

6. Install the static timing gauge (3).

The probe of the gauge should be depressed in-
ward approximately 2 mm (0.079 in).
Static Timing Gauge: 5-8840-0145-0 (J-28827)

7. Rotate the crankshaft to bring the piston in the No.

1 cylinder to a point 30 — 40

° BTDC.

8. Set the timing gauge needle to zero.

9. Move the crankshaft pulley slightly in both direc-

tions to check that the gauge indication is stable.

10. Turn the crankshaft clockwise and read the gauge

indication when the crankshaft pulley timing mark
is aligned with the pointer.

If the injection timing is outside the specified range,
continue with the following steps.

11. Loosen the injection pump fixing nuts and bracket

bolts.

12. Adjust the injection pump setting angle.

N6A3032E

N6A3033E

4JB1

BTDC 14

°

4JB1-TC

BTDC 4

°

4JG2

ATDC 2

°

Standard Reading

mm (in)

0.5 (0.02)

N6A3034E

N6A3035E