Chapter 31 POWERPOINT

Use the textbook to define these Technical Terms:

1. battery cable connection test

2. no-crank problem

3. slow-cranking condition

4. starter current draw test

5. starter ground circuit test

6. starter shims

7. voltage drop tests

Use the textbook to answer these discussion questions:

1. List some typical procedures for basic 12-volt starting system repairs.

Read the chapter summary below:

Summary

■ In a no-crank problem, the engine crankshaft does not rotate properly with the ignition key at start. The most common causes are a dead battery, poor electrical connection, or faulty system component.

■ A solenoid buzzing or clicking sound, without cranking, is commonly due to a discharged battery or poor battery cable connections.

■ A starting system humming sound, after momentary engine cranking, may be due to a bad starter overrunning clutch or a worn pinion gear unit.

■ A starter metallic grinding noise may be caused by broken flywheel teeth or pinion gear teeth wear.

■ A dead or discharged battery is one of the most common reasons the starting system fails to crank the engine properly.

■ A starter current draw test measures the current used by the starting system. This will tell you about the condition of the starting motor and other system parts.

■ Voltage drop tests will quickly locate a part with higher-than-normal resistance.

■ An insulated circuit resistance test checks all parts between the positive battery terminal and the starting motor for excess resistance.

■ A starter ground circuit test checks the circuit be- tween the starting motor ground and the negative battery terminal.

■ A battery cable problem can produce symptoms similar to a dead battery, bad solenoid, or weak starting motor.

■ A bad starter solenoid can cause a range of symptoms, including no cranking (with or without a click) or slow cranking. It can also keep the engine or starting motor from shutting off.

■ A bad ignition switch (starter feed section of switch) can prevent the starter solenoid from working normally.

■ A misadjusted or bad neutral safety switch can keep the engine from cranking when the key is turned to start.

■ If the battery, cables, solenoid, and other starting system parts are good but the engine does not crank properly, the starter may be bad. A current draw test and other tests will help determine whether the starting motor requires further inspection and testing.

■ Starter shims may be used to adjust the space between the pinion gear and the flywheel ring gear. During starter removal, always check for shims.

■ A starting motor rebuild typically involves disassembly of starting motor cleaning and inspection for part wear or damage replacement of brushes, bushings, and any other worn or damaged parts polishing or turning of commutator lubrication, reassembly, testing, and installation of starting motor.

■ OBD systems will indicate problems with hybrid components, including the motor-generator, HV power control module, and battery stack. Stored trouble codes will usually indicate which circuit is not functioning normally.

■ You must use high-voltage, high-current tests to pinpoint the problem when a hybrid engine fails to crank and start.

■ Motor-generator clutch problems can keep the HV motor from cranking the engine, even if the motor is functioning normally.