Isuzu engine 4j series. Manual - part 47

6A1 – 56  4JB1/4JB1T/4JB1TC/4JG2 - ENGINE

6. Piston and Connecting Rod Assembly

1) Remove carbon deposits from the upper portion of the

cylinder wall with a scraper before removing the piston
and connecting rod.

2) Move the piston to the top of the cylinder and tap it

with a hammer grip or similar object from the
connecting rod lower side to drive it out.

3) If the connecting rod upper bearings are to be

reinstalled, mark their fitting positions by tagging each
bearing with the cylinder number from which it was
removed.

4) Clamp the connecting rod in a vise.

Take care not to damage the connecting rod.
Use a piston ring replacer to remove the piston rings.
Piston Ring Replacer
Do not attempt to use some other tool to remove the
piston rings.  Piston ring stretching will result in
reduced piston ring tension.

5) Use a pair of pliers to remove the piston pin snap

rings.

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6) Tap the piston pin out with a hammer and a brass bar.

If the pistons and piston pins are to be reinstalled,
mark their installation positions by tagging each piston
and piston pin with the cylinder number from which it
was removed.

INSTALLATION

6. Piston and Connecting Rod Assembly

1) 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 is held
within the specified limits.

g(oz)

Variance in weight

Less than

after assembly

3(0.1058)

2) Clamp the connecting rod in a vise.

Take care not to damage the connecting rod.

3) Use a pair of pliers to install the piston pin snap ring to

the piston.

NOTE:

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

4) Install the piston to the connecting rod.

The piston head front mark 

!

 and the connecting rod

"ISUZU" casting mark 

"

 must be facing the same

direction.

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6A1 – 58  4JB1/4JB1T/4JB1TC/4JG2 - ENGINE

5) Apply a coat of engine oil to the piston pin and the

piston pin hole.
Use your fingers to force the piston pin into the piston
until it makes contact with the snap ring.

6) Use your fingers to force the piston pin snap ring into

the piston snap ring groove.
Check that the connecting rod moves smoothly on the
piston pin.

7) Install the piston rings with the piston ring expander.

The compression ring must be set with the 1N, 2N
mark facing up.
Discrimination mark is painted as shown in the
illustration.

8) Use a piston ring replacer to install the three piston

rings.
Piston Ring Replacer
Install the piston rings in the numerical order shown in
the illustration.

!

Oil ring

"

2nd compression ring

#

1st compression ring

NOTE:

Install the compression rings with the stamped side
facing up.

Insert the expander coil into the oil ring groove so that
there is no gap on either side of the expander coil
before installing the oil ring.

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4JB1/4JB1T/4JB1TC/4JG2 – ENGINE  6A1 – 59

9) Apply engine oil to the piston ring surfaces.
10) Check that the piston rings rotate smoothly in the

piston ring grooves.

11) Position the piston ring gaps as shown in the

illustration.

12) Carefully wipe any oil or other foreign material from the

connecting rod bearing back face and the connecting
rod bearing fitting surface.

13) Apply a coat of engine oil to the upper bearing

surfaces.
Apply a coat of engine oil the cylinder wall.

14) Position the piston head front mark so that it is facing

the front of the engine.
Use the piston ring compressor to compress the piston
rings.
Piston Ring Compressor: 5-8840-9018-0(J-8037)

15) Use a hammer grip to push the piston in until the

connecting rod makes contact with the crankpin.
At the same time, rotate the crankshaft until the
crankpin is at BDC.

5. Connecting Rod Bearing Cap

1) Position the bearing cap front mark so that it is facing

the front of the engine.

2) Install the connecting rod bearing caps.

Align the bearing cap cylinder number marks and the
connecting rod cylinder number marks.

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