Starter Inspection SD Series

Notice: Do not clean the starter motor parts in a degreasing tank. Soaking parts will dissolve the permanent lubrication and may damage the electrical insulation. This will shorten starter motor life.

1. Clean all parts by wiping with a clean cloth.
2. Inspect the bushing or armature bearing fit in the drive end frame, the lever housing, and the drive end frame housing. If the bushings or bearings are damaged or worn, replace them.

•	Lubricate the bushings before assembling the starter motor. Avoid excessive lubrication.

•	Do not lubricate the roller bearings. They are permanently lubricated.

3. Inspect the armature for runout or scoring. Replace the armature assembly if the condition of the armature shaft is questionable.
4. Inspect the commutator for discolored or uneven conductors.

•	Do not turn the commutator

•	Do not undercut the insulation

•	Clean the commutator with 240 grit emery cloth. Blow away any copper dust present. If the commutator cannot be cleaned, replace the armature.




5. Inspect the armature for short circuits.

•	Rotate the armature in a growler with a steel strip such as a hacksaw blade. Hold the blade on the armature parallel to the shaft. The steel strip will vibrate when it finds the short circuit.

•	Shorts between the commutator bars are sometimes produced by brush dust or copper dust.

6. Inspect armature for opens.

•	Look for loose connections where the conductors join the commutator bars.

•	Poor connections cause arcing and burning of the commutator.




7. Inspect the armature for grounds using a self powered test lamp. If the test lamp lights when one test probe is placed on the commutator and the other test lamp probe is placed on the armature core shaft, the armature is grounded. Replace the armature.
8. Inspect the brushes for wear. If the brushes are worn to half the size of a new brush, replace the assembly.
9. Inspect the brush holders for dirt or damage. Make sure that the brushes are not binding in the holders.
10. Inspect the brush springs for distortion or discoloring. If the springs are weak, bent, or discolored, replace the frame and field assembly.
11. Inspect the field coils.

•	Look for burned or damaged insulation, damaged connections or loose poles.

•	If the conditions of the coils is doubtful, replace the field and frame assembly.

12. Inspect the field coils for grounds.

•	Connect a self-powered test lamp between the field frame and the field connector. Make sure the brush ends do not contact the field frame.

•	If the test lamp lights, the field coils are grounded. Replace the field and frame assembly.

13. Inspect the field coils for opens.

•	Connect a self-powered lamp between the field connector and each of the brushes.

•	If the test lamp does not light at both brushes, the field coils are open. Replace the frame and field assembly

14. Inspect for field coils for shorts.

•	Shorts are indicated by poor motor performance after everything else has been checked out.

•	The coils cannot be replaced separately because of the integral frame construction. The frame and field assembly must be replaced.

15. Inspect the drive assembly (clutch) by turning the drive pinion in the cranking direction. If the drive pinion turns or slips in the cranking direction, replace the over-running clutch assembly.



16. Inspect the solenoid for grounds using a self-powered 12 volt test lamp.

16.1.

Connect the test lamp between the BAT terminal and the case. The lamp should not light (terminal should not be grounded).

16.2.

Connect the test lamp between the S terminal and the case. Then connect the test lamp between the M terminal and the S terminal or between the M terminal and the case. The lamp should turn on.

16.3.

If the solenoid does not pass these checks, replace it.

Notice: To prevent overheating of the solenoid pull-in winding, do not leave the winding energized for more than 15 seconds. The current draw will decrease as the winding temperature increases.




17. Inspect the hold-in winding and the pull-in winding.

17.1.

If the solenoid is not removed from the starter motor, the field lead must be removed from the terminal on the solenoid before making these tests.

17.2.

To check both windings, connect an ammeter in series with a 12 volt battery and the switch terminal on the solenoid. Connect a carbon pile across the battery. Ground the solenoid motor terminal. Adjust the voltage to 10 volts and note the ammeter reading. It should be 60 to 85 amperes.

17.3.

Note the ampere reading. A high reading indicates a shorted or grounded winding, and a low reading indicates excessive resistance.

•	The resistance of the windings can be read directly using a digital ohmmeter that can measure tenths of an ohm.

•	Coil resistance can be determined by dividing the voltage by the current (amperes).

Starter Inspection 28-MT Series

Notice: Do not clean the starter motor parts in a degreasing tank. Soaking parts will dissolve the permanent lubrication and may damage the electrical insulation. This will shorten starter motor life.

Clean

Clean all starter motor parts with a clean soft cloth prior to testing.

Inspection of the following steps refer to visual inspection of the starter motor parts and assemblies to determine their serviceability.

1. Inspect all parts for cracks, distortion, or other structural damage. Replace parts or assemblies that are cracked, bent or otherwise damaged.
2. Inspect threaded parts for stripped, crossed, or otherwise damaged threads. Replace the parts with thread damage that cannot be cleaned up using a suitable tap or die. Replace any items that have damaged threads.
3. Inspect the solenoid assembly for cut or torn boot. If the boot is damaged, replace the solenoid assembly.
4. Inspect the clutch drive assembly. Replace the assembly if the following conditions exist:

•	The pinion gear turns roughly or turns in both directions

•	The pinion gear teeth that are broken or show evidence of step wear

•	The shift lever collar shows deep scoring or other damage

5. Inspect the brush holder assembly for loose riveted joints and cracked or broken insulation. Replace if damaged.
6. Inspect the brushes for excessive wear. The minimum allowable brush length is 12 mm (0.472 inch). Replace excessively worn brushes in sets.
7. Inspect the drive end housing bushing for scoring or other damage. Replace the damaged bushing.
8. Inspect the ball bearings in the following way:

•	Hold the armature or driveshaft and slowly rotate the outer bearing race by hand

•	Check that the bearing turns freely without binding or the feel of flat spots

•	Replace damaged bearings

9. Inspect the armature assembly for the following conditions:

•	Gear teeth that are broken, or that show evidence of step wear or root interference.

•	A rough commutator surface. Polish with 400 grit polishing cloth if necessary. Thoroughly clean metal dusts from between the commutator bars. If the commutator surface cannot be repaired in this manner, replace the armature assembly. Do not turn the commutator in a lathe.

•	A worn commutator. Replace the armature assembly if the commutator outer diameter is less than 36 mm (1.378 inch) or if the undercut depth at any point is less than 0.2 mm (0.008 inch). Do not undercut the insulation.

10. Inspect the driveshaft for the following conditions and replace if necessary.

•	Scored or damaged shaft where it turns inside the bushing

•	Internal gear with teeth broken or showing evidence of step wear

•	A damaged spline. The clutch drive assembly must slide smoothly and easily over the full length the spline.