Isuzu engine 4j series. Manual - part 39

6A1 – 24  4JB1/4JB1T/4JB1TC/4JG2 - ENGINE

7. Noise Cover Spacer

8. Timing Gear Case Cover

9. Oil Pipe

10. Idler Gear

1) Measure the camshaft timing gear backlash and the

crankshaft timing gear backlash before removing the
idler gear.

2) Measure the idler gear end play before removing the

idler gear.

NOTE:

Refer to the following items for details on the
backlash and end play measurement procedures.

Timing Gear Backlash Measurement

1) Set a dial indicator to the timing gear to measured.

Hold both the gear to be checked and the adjoining
gear stationary.

2) Move the gear to be checked as far as possible to

both the right and the left.
Take the dial indicator reading.
If the measured value exceeds the specified limit, the
timing gear must be replaced.

Timing Gear Backlash

mm (in)

Standard

Limit

0.10-0.17 (0.0039-0.0067)

0.30 (0.012)

Idler Gear "A" End Play Measurement

Insert a feeler gauge between the idler gear and the thrust
collar to measure the gap and determine the idler gear
end play.
If the measured value exceeds the specified limit, the
thrust collar must be replaced.
Idle Gear End Play

mm (in)

Standard

Limit

0.07 (0.0028)

0.2 (0.0079)

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11. Idle Gear

12. Injection Pump

1) Remove the six injection pump bracket bolts 

!

 from

the timing gear case.

2) Remove the injection pump rear bracket bolts 

"

 from

the injection pump bracket 

#

.

3) Remove the injection pump rear bracket bolts 

$

 and

the bracket 

%

 from the cylinder body.

4) Pull the injection pump along with the injection pump

timing gear free toward the rear of the engine.

NOTE:

Plug the injection pump delivery holder ports with the
shipping caps (or the equivalent) to prevent the entry
of foreign material.

13. Camshaft Timing Gear

1) Use a dial indicator to measure the camshaft end play.

This must be done before removing the camshaft
gear.
If the camshaft end play exceeds the specified limit,
the thrust plate must be replaced.

Camshaft End Play

mm (in)

Standard

Limit

0.050-0.114

(0.002-0.0044)

0.2 (0.008)

2) Remove the camshaft timing gear bolt from the

camshaft.

NOTE:

Hold the camshaft stationary to prevent the camshaft
from turning.
3) Use the universal puller 

!

 to pull out the camshaft

timing gear 

"

.

Universal Puller: 5-8521-0002-0

4) Remove the thrust plate 

#

.

14. Crankshaft Gear

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6A1 – 26  4JB1/4JB1T/4JB1TC/4JG2 - ENGINE

INSTALLATION

14 Crankshaft Gear

1) Install the crankshaft gear.
2) Use the crankshaft gear installer 

!

 to install the

crankshaft gear 

"

.

The crankshaft gear timing mark ("X-X") must be
facing outward.
Crankshaft Gear Installer: 9-8522-0020-0

13. Camshaft Timing Gear

1) Install the thrust plate to the cylinder body.
2) Tighten the thrust plate bolts to the specified torque.

N∙m (kg∙m/lb∙ft)

                                                                                                                   

18 (1.8/13)

                                                                                                                   

3) Install the camshaft timing gear to the camshaft.

The timing gear mark ("Y-Y") must be facing outward.

4) Tighten the timing gear to the specified torque.

N∙m (kg∙m/lb∙ft)

                                                                                                                   

64 (6.5/47)

                                                                                                                   

12. Injection Pump

1) Install the O-ring 

!

 to the injection pump flange 

"

.

2) Install the injection pump to the timing gear case.

Align the idler gear "B" 

#

 "V-V" mark with the injection

pump timing gear 

$

 "V" mark.

3) Temporarily tighten the six injection pump nuts 

%

.

The injection pump nuts will be finally tightened after
the injection pump rear bracket bolts.

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4JB1/4JB1T/4JB1TC/4JG2 – ENGINE  6A1 – 27

4) Install the injection pump rear bracket 

&

 and the rear

bracket bolts 

'

 to the cylinder body.

5) Install the rear bracket bolts 

(

 to the injection pump

bracket 

)

.

Do not tighten the bolts.
The rear bracket bolts 

'

 and 

(

 will be finally

tightened to the specified torque after tighten the
injection pump nuts.

6)  Tighten the injection pump nuts to the specified torque.

N∙m (kg∙m/lb∙ft)

                                                                                                                   

19 (1.9/14)

                                                                                                                   

7) Tighten the injection pump bracket bolts to the

specified torque.

N∙m (kg∙m/lb∙ft)

                                                                                                                   

19 (1.9/14)

                                                                                                                   

11. Idler Gear

1) Apply engine oil to the idler gear and the idler gear

shaft.
The idler gear shaft oil hole must be facing up.

2) Position the idler gear setting marks "X" and "Y" so

that they are facing the front of the engine.

3) Align the idler gear "X" setting mark with the

crankshaft timing gear 

!

 "X-X" setting mark.

4) Align the idler gear "Y" setting mark with the camshaft

timing gear 

"

 "Y-Y" setting mark.

5) Install the thrust collar and bolts to the cylinder body

through the shaft.
The thrust collar oil hole must be facing up, and the
thrust collar chamfered must be outward.

6) Tighten the idler gear bolt to the specified torque.

N∙m (kg∙m/lb∙ft)

                                                                                                                   

19 (1.9/14)

                                                                                                                   

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