Isuzu KB P190. Service manual — part 223
ENGINE MECHANICAL 6A – 87
3. Use a feeler gauge to measure the piston ring gap.
If the measured value exceeds the specified limit, the
piston ring must be replaced.
Piston Ring Gap
mm (in)
4JA1T (L), 4JA1TC
Standard
Limit
1st Compression Ring
2nd Compression Ring
0.3-0.3
(0.0118-0.0197)
Oil Ring
0.250-0.450
(0.0098-0.0177)
1.5
(0.059)
4JH1TC
Standard
Limit
1st Compression Ring
2nd Compression Ring
0.3-0.5
(0.0118-0.0197)
Oil Ring
0.250-0.450
(0.0098-0.0177)
1.5
(0.059)
Piston Ring and Piston Ring Groove Clearance
Use a feeler gauge to measure the clearance between the
piston ring and the piston ring groove at several points around
the piston.
If the clearance between the piston ring and the piston ring
groove exceeds the specified limit, the piston ring must be
replaced.
Piston Ring and Piston Ring Groove Clearance
mm (in)
4JA1T (L), 4JA1TC
Standard
Limit
1st Compression Ring
0.09-0.125
(0.0035-0.0049)
2nd Compression Ring
0.05-0.085
(0.0020-0.0033)
Oil Ring
0.03-0.070
(0.0012-0.0028)
0.15
(0.0059)
4JH1TC
Standard
Limit
1st Compression Ring
0.09-0.130
(0.0035-0.0051)
2nd Compression Ring
0.05-0.090
(0.0020-0.0035)
Oil Ring
0.03-0.070
(0.0012-0.0028)
0.15
(0.0059)
015RY00021
015LX025
6A – 88 ENGINE MECHANICAL
4. Visually inspect the piston rings.
If a piston ring groove is damaged or distorted, the piston
must be replaced.
Piston Pin Diameter
Use a micrometer to measure the piston pin diameter at
several points.
If the measured value is less than the specified limit, the piston
pin must be replaced.
Piston Pin Diameter
mm
(in)
Standard
Limit
30.995-31.000
(1.2202-1.2204)
30.97
(1.2193)
Piston Pin and Piston Clearance
Use and inside dial indicator to measure the piston pin hole (in
the piston).
Piston Pin Hole
mm
(in)
4JA1T (L)
31.002-31.010 (1.2206-1.2208)
4JA1TC, 4JH1TC
31.005-31.013 (1.2207-1.2210)
Piston Pin and Piston Pin Hole Clearance
mm (in)
4JA1T (L)
0.002-0.015 (0.00008-0.0006)
4JA1TC, 4JH1TC
0.005-0.018 (0.0002-0.0007)
CYLINDER HEAD GASKET SELECTION
Cylinder head gasket is determined by the piston head
projection from the cylinder body upper surface, in order to
improve engine performance.
Three types of gasket are provided by the difference of
thickness. Select the adequet one out of three grades of
gasket, according to the following procedure.
Before measurement, clear off carbon from the piston head
and cylinder body surface and also clean the place where a
gasket was installed.
015LX026
015RW048
011LX011
ENGINE MECHANICAL 6A – 89
RTW36ASH001701
Piston Head Projection Measuring Point
1. Use a dial indicator to measure the piston projection
amount.
2. Refer to the illustration for the piston head projection
measuring positions.
All measuring positions should be as close as possible to
the cylinder liner.
3. Measure the points 1, 2, 3, 4 and obtain two differences 1-
2 and 3-4 on each cylinder.
Calculate the average value of the piston head projection
on each cylinder.
4. Obtain the maximum value in the four cylinders.
5. Determine the gasket grade required to the maximum
value described above in accordance with the following
table.
Cylinder Head Gasket Combination
mm (in)
Cylinder Head Gasket Combination
4JA1T (L), 4JA1TC
mm (in)
Gasket Grade Mark Piston Projection
Gasket Thickness
(Reference)
A
0.718-0.773
(0.0283-0.0304)
1.6
(0.0630)
B
0.773-0.819
(0.0304-0.0322)
1.65
(0.0650)
C
0.819-0.874
(0.0322-0.0344)
1.70
(0.0669)
4JH1TC mm
(in)
Gasket Grade Mark Piston Projection
Gasket Thickness
(Reference)
A
0.215-0.265
(0.0085-0.0104)
1.3
(0.5118)
B
0.265-0.315
(0.0104-0.0124)
1.35
(0.5315)
C
0.315-0.365
(0.0124-0.0144)
1.4
(0.5512)
NOTE:
Difference of the each piston projection and must be
equal or within 0.1 mm (0.004 in).
011RY00027
011RY00030
6A – 90 ENGINE MECHANICAL
CONNECTING ROD
Connecting Rod Alignment
Use a connecting rod aligner to measure the distortion and the
parallelism between the connecting rod big end hole and the
connecting rod small end hole.
If either the measured distortion or parallelism exceed the
specified limit, the connecting rod must be replaced.
Connecting Rod Alignment Per Length of 100 mm (3.94 in)
mm (in)
Standard
Limit
Distortion
0.08 (0.003) or Less
0.20 (0.008)
Parallelism
0.05 (0.002) or Less
0.15 (0.006)
Connecting Rod Side Face Clearance
1. Install the connecting rod to the crankpin.
2. Use a feeler gauge to measure the clearance between the
connecting rod big end side face and the crankpin side
face.
If the measured value exceeds the specified limit, the
connecting rod must be replaced.
Connecting Rod Big End and Crankpin Side Face Clearance
mm (in)
Standard
Limit
0.23 (0.009)
0.35 (0.014)
Piston Pin and Connecting Rod Small End
Bushing Clearance
Use a caliper calibrator and a dial indicator to measure the
piston pin and connecting rod small end bushing clearance.
If the clearance between the piston pin and the connecting rod
small end bushing exceeds the specified limit, replace the
piston pin and/or the connecting rod.
Piston Pin and Connecting Rod Small End
Bushing Clearance
mm (in)
Standard
Limit
4JA1T (L)
0.008-0.020
(0.003-0.0008)
0.050 (0.002)
4JA1TC,
4JH1TC
0.005-0.018
(0.0002-0.0007)
0.050 (0.002)
015LX034
011RY00029
015LX028
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