Isuzu engine 4j series. Manual — part 29

6A – 52

GENERAL ENGINE MECHANICAL

Bushing replacement

Removal:

Use a suitable bar and bench press or
hammer.

Installation: Use a suitable bar and bench press.

NOTE:

Align the bushing with the connecting rod oil port.

After installing a new bushing, finish the bushing bore
with a pin hole grinder.

Connecting rods

1. Check the connecting rod alignment with a connecting

rod aligner.
If either the bend or the twist exceeds the specified
limit, the connecting rod must be replaced.

mm (in)

Standard

Limit

Bend per 100 (3.94) 0.08 (0.0031) or less 0.20 (0.0079)

Twist per 100 (3.94) 0.05 (0.0020) or less 0.15 (0.0059)

2. Measure the connecting rod thrust clearance.

Use a feeler gauge to measure the thrust clearance at
the big end of the connecting rod.
If the clearance exceeds the specified limit, the
connecting rod must be replaced.

Thrust Clearance

mm (in)

Standard

Limit

0.230 (0.0091)

0.350 (0.0138)

3. Measure the oil clearance between the connecting rod

and the crankshaft by:
1) Remove the connecting rod cap nuts and the rod

caps.
Arrange the removed rod caps in the cylinder
number order.

2) Clean the rod bearings and the crankshaft pins.
3) Carefully check the rod bearings.

If even one bearing is found to be damaged or
badly worn, the entire bearing assembly must be
replaced as a set. Reinstall the bearings in their
original positions.
Apply plastigage to the crank pin.

4) Reinstall the rod caps to their original positions

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GENERAL ENGINE MECHANICAL 6A – 53

5) Tighten the cap nuts in 2 steps, using angular

tightening method as shown in the following
specifications. (4JG2)

4JG2

N∙m (kg∙m/lb∙ft)

1st Steps

2nd Step

29 (3.0/22)

45° - 75°

4JA1, 4JB1, 4JB1TC

N∙m (kg∙m/lb∙ft)

83 (8.5/61)

NOTE:

Do not allow the crankshaft to rotate.

6) Remove the rod caps.
7) Measure the width of the plastigage and determine

the oil clearance. If the oil clearance exceeds the
limit, replace the rod bearings as a set.

8) Clean the plastigage from the bearings and the

crankshaft pins.

Crankshaft Journal and Bearing Clearance

mm (in)

Standard

Limit

4JB1 /

4JB1T /

4JB1TC

0.029 - 0.066

(0.0011 - 0.0026)

4JG2

0.029 - 0.083

(0.0011 - 0.0033)

0.100 (0.0039)

REASSEMBLY

11. Connecting Rod

10. Piston

9. Piston Pin

Apply a cost of engine oil to the piston pin and the piston
pin hole.

8. Piston Pin Snap Ring

Apply a thin coat of engine oil to the piston pin.
Try to insert the piston pin into the piston pin hole with
normal finger pressure.
Weigh each piston and connecting rod assembly.
Select piston and connecting rod combinations so that the
weight variation of the different assemblies a held within
the specified limits.

g (oz)

Variance in weight

after assembly

Less than 3

(0.1058)

NOTE:

When changing piston/connecting rod combinations,
do not change the piston/piston pin combination

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6A – 54

GENERAL ENGINE MECHANICAL

•

Attach the piston to the connecting rod with the piston
front mark and the connecting rod ISUZU mark on the
same side.

7. Piston Ring

•

Install the piston rings with the piston ring expander.
The compression ring must be set with the 1N, 2N
mark (4JG2) facing up.

•

Discrimination mark is painted as shown in the
illustration.

•

Install piston rings in the following sequence.

1) Oil ring

!

Expander ring

"

Upper side rail

#

Lower side rail

2) 2nd compression ring

3) 1st compression ring

•

The compression ring must be set with the 1N or 2N
mark (4JG2) facing up.

•

1st compression ring: 1N (4JG2), N (4JB1)

•

2nd compression ring: 2N (4JG2), N (4JB1)

•

After installation, apply engine oil to the entire
circumference of the piston rings.
Check to see that all the rings rotate smoothly.

•

Insert the bearings into the connecting rods and caps.
Apply new engine oil to the bearing faces.
Cap side bearings have no oil hole.
Conn rod side bearings oil hole should be aligned with
oil hole on the conn rod.

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GENERAL ENGINE MECHANICAL 6A – 55

6. Piston and Connecting Rod

•

Apply engine oil to the cylinder bores, the connecting
rod bearings and the crankshaft pins.

•

Check to see that the piston ring end gaps are
correctly positioned.

•

Insert the piston/connecting rod assemblies into each
cylinder with the piston ring compressor.

•

The front marks must be facing the front of the engine.

5. Connecting Rod Bearing Cap

•

Tighten the cap nuts in 2 steps, using angular
tightening method as shown in the following
specifications.

4JG2

N∙m (kg∙m/lb∙ft)

1st Steps

2nd Step

29 (3.0/22)

45° - 75°

4JA1, 4JB1, 4JB1TC

N∙m (kg∙m/lb∙ft)

83 (8.5/61)

After tightening the cap nuts, check to see that the
crankshaft rotates smoothly.

4. Piston Cooling Oil Pipe

•

Install the piston cooling oil pipe to the cylinder body.

•

Tighten the oil pipe bolts and relief valve to the
specified torque.

Oil Pipe Bolt Torque

N∙m (kg∙m/lb∙ft)

(1) M8 x 1.25

19 (1.9/14)

N∙m (kg∙m/lb∙in)

(2) M6 x 1.00

8 (0.8/69)

Oil Pressure Regulating
Valve Torque

N∙m (kg∙m/lb∙ft)

(3) M16 x 1.5

29 (3.0/22)

NOTE:
Check that there is no interference between the piston
and the oiling jet pipe by slowly rotating the
crankshaft.

3. Oil Pump Assembly

2. Oil Pan Assembly

Above works refer to “OIL PUMP” Section in this manual.

1. Cylinder Head Assembly

•

Piston Head Projection Measurement Point

•

Cylinder Head ASM

•

Push Rod

•

Rocker Arm Shaft ASM

Valve clearance adjustment.
Above works refer to “CYLINDER BLOCK” Section in this
manual.

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