Isuzu engine 4j series. Manual - part 22

6A – 24

  GENERAL ENGINE MECHANICAL

ROCKER ARM ASSEMBLY

DISASSEMBLY

1. Rocker Arm Shaft Assembly

2. Rocker Arm Shaft Snap Ring

3. Rocker Arm

4. Rocker Arm Shaft Bracket

5. Rocker Arm

6. Rocker Arm Shaft Spring

7. Rocker Arm Shaft

INSPECTION AND REPAIR

Make the necessary adjustment, repairs, and part
replacements if excessive wear or damage is discovered
during inspection.

Use a micrometer to measure the rocker shaft outside
diameter at the point where the rocker arm moves on the
rocker shaft.
Replace the rocker shaft if the diameter exceeds the
specified limit.

mm (in)

Standard

Limit

18.98 - 19.00

(0.7472 - 0.7480)

18.9 (0.744)

6A-24-1.tif

6A-24-2.tif

GENERAL ENGINE MECHANICAL   6A – 25

Oil Clearance

1. Use either a vernier caliper or a dial indicator to

measure the rocker arm inside diameter.

Rocker Arm Inside Diameter

mm (in)

Standard

Limit

19.036 - 19.060

(0.7494 - 0.7503)

19.100 (0.7519)

2. Measure the rocker arm shaft outside diameter.

If the measured value exceeds the specified limit,
replace either the rocker arm or the rocker arm shaft.

Rocker Arm and
Rocker Shaft Clearance

mm (in)

Standard

Limit

0.06 - 0.08

(0.0024 - 0.0031)

0.10 (0.0039)

3. Check that the rocker arm oil port is free is

obstructions.
If necessary, use compressed air to clean the rocker
arm oil port.

Rocker Arm Correction

Inspection the rocker arm valve stem contact surface for
step wear 

! 

and scoring 

"

.

If the contact surfaces have light step wear or scoring,
they may be honed with an oil stone.
If the step wear or scoring is severe, the rocker arm must
be replaced.

6A-25-1.tif

6A-25-2.tif

6A-25-3.tif

6A – 26

  GENERAL ENGINE MECHANICAL

Rocker Arm Shaft Run-Out

1. Place the rocker arm shaft on a V-block.
2. Use a dial indicator to measure the rocker arm shaft

central portion run-out.
If the run-out is very slight, correct the rocker arm shaft
run-out with a bench press. The rocker arm must be at
cold condition.
If the measured rocker arm shaft run-out exceeds the
specified limit, the rocker arm shaft must be replaced.

Rocker Arm Shaft Run-Out

mm (in)

Limit

4JB1 / 4JB1T / 4JB1TC

4JG2

0.2 (0.008)

REASSEMBLY

7. Rocker Arm Shaft

•

Apply a light coat of engine oil to the rocker arm
shafts.

•

Position the rocker arm shaft with the large oil hole
(4ø) facing the front of the engine.

•

Install the rocker shaft together with the rocker arm,
the rocker arm shaft bracket, and the spring.

6. Rocker Arm Shaft Spring

5. Rocker Arm

4. Rocker Arm Shaft Bracket

3. Rocker Arm

2. Rocker Arm Shaft Snap Ring

1. Rocker Arm Shaft Assembly

•

Install the rocker arm shaft assembly in cylinder head.

•

Tighten the rocker arm shaft fixing bolts to the
specified torque.

6A-26-1.tif

6A-26-2.tif

6A-26-3.tif

GENERAL ENGINE MECHANICAL   6A – 27

OIL PUMP

DISASSEMBLY

1. Vacuum Pump Oil Hose

•

Remove the oil hose 

!

 from oil pan.

2. Stifner & Space Rubber

•

Remove the stiffener from of the oil pan left & right
side.

•

Take out space rubber.

3. Oil Pan Assembly

6A-27-2.tif

6A-27-1.tif

Disassembly steps

1. Vacuum pump oil hose
2. Stiffener and space rubber
3. Oil pan Assembly
4. Oil pump Assembly
5. Strainer
6. Pump cover
7. Driven gear
8. Oil pump body