Isuzu KB P190. Manual — part 402

6D-20 ENGINE ELECTRICAL (4JK1/4JJ1)

Inspection and Repair

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

Armature

1.

Measure the commutator run-out.

Replace the commutator if the measured run-out

exceeds the specified limit.

Commutator Run-Out

mm (in)

Standard Limit

0.05 (0.002)

0.25 (0.010)

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2.

Check the commutator mica segments for

excessive wear.

3. Measure the mica segment depth.

Mica Segment Depth

mm (in)

Standard Limit

0.5 - 0.8 (0.020 - 0.030)

0.2 (0.008)

If the mica segment depth is less than the

standard but more than the limit, the commutator

may be reground.

If the mica segment depth is less than the limit, the

commutator must be replaced.

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Legend

1. Insulator

2. 0.5 - 0.8 mm (0.020 - 0.030 in)

3. Commutator

Segments

4. Correct

5. Incorrect

4. Measure the commutator outside diameter.

Commutator Outside Diameter

mm (in)

Standard Limit

36.5 (1.44)

35.5 (1.40)

If the measured outside diameter is less than the

specified limit, the commutator must be replaced.

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ENGINE ELECTRICAL (4JK1/4JJ1) 6D-21

5. Use a circuit tester to check the armature for

grounding.

1) Hold one probe of the circuit tester against the

commutator segment.

2) Hold the other circuit tester probe against the

armature core.

If the circuit tester indicates continuity, the

armature is grounded.

The armature must be replaced.

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6. Use the circuit tester to check the armature for

continuity.

1) Hold the circuit tester probes against two

commutator segments.

2) Repair Step 1 at different segments of the

armature core.

There should be continuity between all segments

of the commutator.

If there is not, the armature must be replaced.

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Yoke

1. Use a circuit tester to check the field winding

ground.

1) Hold one circuit tester probe against the field

winding end or brush.

2) Hold the other circuit tester probe against the

bare surface of the yoke body.

There should be no continuity. If there is

continuity, the field coil is grounded. The yoke

must be replaced.

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2. Use the circuit tester to check the field winding

continuity.

1) Hold one circuit tester probe against the “M”

terminal lead wire.

2) Hold the other circuit tester probe against the

field winding brush.

There should be continuity.If there is no continuity,

the yoke must be replaced.

6D-22 ENGINE ELECTRICAL (4JK1/4JJ1)

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Brush and Brush Holder

1. Use a vernier caliper to measure the brush length

(four brushes).

Replace the brushes as a set if one or more of the

brush lengths is less than the specified limit.

Brush Length

mm (in)

Standard Limit

15 (0.59)

12 (0.47)

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2. Use a circuit tester to check the brush holder

insulation.

Touch one probe to the holder plate and the other

probe to the positive brush holder.

There should be no continuity.

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3. Inspect the brushes for excessive wear.

If the negative brushes have excessive wear, the

entire brush holder assembly must be replaced.

If the positive brushes have excessive wear, the

entire yoke must be replaced.

Overrunning Clutch

1. Inspect the overrunning clutch gear teeth for

excessive wear and damage.

Replace the overrunning clutch if necessary.

2. Rotate the pinion clockwise.

It should turn smoothly.

3. Try to rotate the pinion in the opposite direction.

The pinion should lock.

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ENGINE ELECTRICAL (4JK1/4JJ1) 6D-23

Bearing

Inspect the bearings for excessive wear and damage.

Replace the bearings if necessary.

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