2. OBJECTIVES
After studying Chapter 18, the reader should be able to:
Prepare for ASE Electrical/Electronic Systems (A6) certification test content area “C” (Starting System Diagnosis and Repair).
Describe how the cranking circuit works.
Discuss how a starter motor converts electrical power into mechanical power.
Describe the hold-in and pull-in windings of a starter solenoid.

3. CRANKING CIRCUIT
For any engine to start, it must first be rotated, using an external power source.
It is the purpose and function of the cranking circuit to create the necessary power and transfer it from the battery to the starter motor that rotates the engine.

4. CRANKING CIRCUIT Modern cranking circuits include the following:
Starter motor.
Battery.
Starter solenoid or relay.
Starter drive.
Ignition switch.
FIGURE 18-1 A typical solenoid-operated starter.

5. CRANKING CIRCUIT
FIGURE 18-2 Some column-mounted ignition switches act directly on the contact points, whereas others use a link from the lock cylinder to the ignition switch.

6. CRANKING CIRCUIT Control Circuit
Many automobile manufacturers use an electric switch called a neutral safety switch that opens the circuit between the ignition switch and the starter to prevent starter motor operation unless the gear selector is in neutral or park.
FIGURE 18-3 A typical wiring diagram of a starter circuit.

7. COMPUTER-CONTROLLED STARTING
The ignition switch start position on the push-to-start button is used as an input signal to the powertrain control module (PCM).
Before the PCM cranks the engine, the following conditions must be met.
The brake pedal is depressed.
The gear selector is in park or neutral.
The correct key fob (code) is present in the vehicle.

8. COMPUTER-CONTROLLED STARTING
Computer-controlled starting is almost always part of the system if a push button start is used.
FIGURE 18-4 Instead of an ignition key to start the engine, some vehicles are using a start button which is also used to stop the engine, as shown on this Jaguar.

9. COMPUTER-CONTROLLED STARTING
This feature allows the heater or air conditioning system to start before the driver arrives.
FIGURE 18-5 The top button on this key fob is the remote start button.

10. HOW THE STARTER MOTOR WORKS
A starter consists of the main structural support of a starter called the main field housing, one end of which is called a commutator-end (or brush-end) housing and the other end a drive-end housing.

11. HOW THE STARTER MOTOR WORKS
The commutator-end plate supports the end containing the starter brushes.
Through bolts hold the three components together.
FIGURE 18-6 A typical starter motor.

12. HOW THE STARTER MOTOR WORKS
The starter uses four brushes—two brushes to transfer the current from the field coils to the armature, and two brushes to provide the ground return path for the current that flows through the armature.
FIGURE 18-7 This series-wound electric motor shows the basic operation with only two brushes: one hot brush and one ground brush. The current flows through both field coils, then through the hot brush and through the loop winding of the armature before reaching ground through the ground brush.

13. HOW MAGNETIC FIELDS TURN AN ARMATURE
One basic principle of electromagnetism is that a magnetic field surrounds every conductor carrying a current.
Inside the starter housing is a strong magnetic field created by the field coil magnets.

14. HOW THE STARTER MOTOR WORKS
Inside the starter housing is a strong magnetic field created by the field coil magnets.
FIGURE 18-8 The interaction of the magnetic fields of the armature loops and field coils creates a stronger magnetic field on the right side of the conductor, causing the armature loop to move toward the left.

15. HOW THE STARTER MOTOR WORKS
FIGURE 18-9 The armature loops rotate due to the difference in the
strength of the magnetic field. The loops move from a strong magnetic field
strength toward a weaker magnetic field strength.

16. HOW THE STARTER MOTOR WORKS
The magnetic field of the starter motor is provided by two or more pole shoes and field windings.
The pole shoes are made of iron and are attached to the frame with large screws.
FIGURE Pole shoes and field windings installed in the housing.

17. HOW THE STARTER MOTOR WORKS
Paths of magnetic flux lines within a four-pole motor.
FIGURE Magnetic lines of force in a four-pole motor.

18. HOW THE STARTER MOTOR WORKS
The field windings are usually made of a heavy copper ribbon to increase their current-carrying capacity and electromagnetic field strength.
FIGURE A pole shoe and field winding.

19. TYPES OF STARTER MOTORS
Starter motors must provide high power at low starter motor speeds to crank an automotive engine at all temperatures and at the cranking speed required for the engine to start (60 to 250 engine RPM).
Many starter motors are series wound, which means that the current flows first through the field coils, then in series through the armature, and finally to a ground through the ground brushes.
FIGURE This wiring diagram illustrates the construction of a
series-wound electric motor. Notice that all current flows through the field coils,
then through the armature (in series) before reaching ground.

20. TYPES OF STARTER MOTORS Series Motors
A series motor develops its maximum torque at the initial start (0 RPM) and develops less torque as the speed increases.
Because the power (torque) of the starter depends on the strength of the magnetic fields, the torque of the starter decreases as the starter speed increases.

21. TYPES OF STARTER MOTORS Shunt Motors
Shunt-type electric motors have the field coils in parallel (or shunt) across the armature.
FIGURE This wiring diagram illustrates the construction of a shunt-type
electric motor. Shunt-type electric motors have the field coils in parallel
(or shunt) across the armature as shown.

22. TYPES OF STARTER MOTORS Compound Motors
A compound-wound, or compound, motor has the operating characteristics of a series motor and a shunt-type motor, because some of the field coils are connected to the armature in series and some (usually only one) are connected directly to the battery in parallel (shunt) with the armature.
FIGURE A compound motor is a combination of series and shunt
types, using part of the field coils connected electrically in series with the
armature and some in parallel (shunt).

23. ARMATURE AND COMMUTATOR ASSEMBLY
The motor armature has a laminated core.
FIGURE A typical starter motor armature.

24. ARMATURE AND COMMUTATOR ASSEMBLY
Motor armatures are connected to the commutator in one of two ways.
In a lap winding, the two ends of each conductor are attached to two adjacent commutator bars.
FIGURE An armature lap winding.

25. ARMATURE AND COMMUTATOR ASSEMBLY
The armature core, windings, and commutator are assembled on a long armature shaft.
This shaft also carries the pinion gear that meshes with the engine flywheel ring gear.
FIGURE The pinion gear meshes with the flywheel ring gear.

26. ARMATURE AND COMMUTATOR ASSEMBLY
Most automotive starters have two grounded and two insulated brushes, which are held against the commutator by spring force.
FIGURE A cutaway of a typical starter motor.

27. PERMANENT-MAGNET FIELDS
The permanent-magnet, planetary-drive starter motor is the first significant advance in starter design in decades.
This eliminates the motor field circuit, which in turn eliminates the potential for field wire-to-frame shorts, field coil welding, and other electrical problems.

28. DON’T HIT THAT STARTER!
If struck with a heavy tool, the magnets could be broken with parts of the magnet falling onto the armature and into the bearing pockets, making the starter impossible to repair or rebuild.
FIGURE This starter permanent-magnet field housing was ruined when someone used a hammer on the field housing in an attempt to “fix” a starter that would not work. A total replacement is the only solution in this case.

29. GEAR-REDUCTION STARTERS
The purpose of the gear reduction (typically 2:1 to 4:1) is to increase starter motor speed and provide the torque multiplication necessary to crank an engine.
FIGURE Many gear-reduction starters use a planetary gear reduction assembly similar to that used in an automatic transmission.
FIGURE Chrysler was one of the first vehicle manufacturers to
use a gear-reduction starter.

30. STARTER DRIVES
A starter drive includes a small pinion gear that meshes with and rotates the larger gear on the engine for starting.
The ends of the starter pinion gear are tapered to help the teeth mesh more easily without damaging the flywheel ring gear teeth.
FIGURE A cutaway of a typical starter drive.

31. STARTER DRIVES
If the engine starts and is accelerated to 2000 RPM (normal cold engine speed), the starter will be destroyed by the high speed (36,000 RPM) if the starter was not disengaged from the engine.
FIGURE The ring gear to pinion gear ratio is usually 15:1 to 20:1.

32. A BIT OF HISTORY A Bendix Drive Is Now Called a Starter Drive
Older-model starters often used a Bendix drive mechanism, which used inertia to engage the starter pinion with the engine flywheel gear.
The overrunning clutch, which is built in as a part of the starter drive unit, uses steel balls or rollers installed in tapered notches.
FIGURE Operation of the overrunning clutch. (A) Starter motor is driving the starter pinion and cranking the engine. The rollers are wedged against spring force into their slots. (B) The engine has started and is rotating faster than the starter armature. Spring force pushes the rollers so they
can rotate freely.

33. A BIT OF HISTORY A Bendix Drive Is Now Called a Starter Drive
The spring between the drive tang or pulley and the overrunning clutch and pinion is called a mesh spring and it helps to cushion and control the engagement of the starter drive pinion with the engine flywheel gear.
FIGURE Cutaway of a solenoid-activated starter showing the solenoid, shift lever, and starter drive assembly that includes the starter pinion and overrunning clutch with a mesh spring in one unit.

34. STARTER DRIVE OPERATION
A starter drive is generally a dependable unit and does not require replacement unless defective or worn.
Intermittent starter drive failure (starter whine) is often most noticeable during cold weather.

35. POSITIVE-ENGAGEMENT STARTERS
Positive-engagement starters, used on many older Ford engines, utilize the shunt coil winding and a movable pole shoe to engage the starter drive.
FIGURE A Ford movable-pole-shoe starter.

36. POSITIVE-ENGAGEMENT STARTERS
The movable pole shoe is held down (which keeps the starter drive engaged) by a smaller coil on the inside of the main drive coil.
FIGURE A circuit diagram of a Ford system using a movable-pole-shoe starter.

37. SOLENOID-OPERATED STARTERS
A starter solenoid is an electromagnetic switch containing two separate, but connected, electromagnetic windings.
FIGURE Wiring diagram of a typical starter solenoid. Notice that both the pull-in winding and the hold-in winding are energized when the ignition switch is first turned to the “start” position. As soon as the solenoid contact disk makes electrical contact with both the B and M terminals, the battery current is conducted to the starter motor and electrically neutralizes the pull-in winding.

38. HOW ARE STARTERS MADE SO SMALL?
A starter can be constructed smaller due to the use of gear reduction to achieve the same cranking torque as a straight drive starter, but using much smaller components.
FIGURE A palm-sized starter armature.

39. SUMMARY
All starter motors use the principle of magnetic interaction between the field coils attached to the housing and the magnetic field of the armature.
The control circuit includes the ignition switch, neutral safety (clutch) switch, and solenoid.
The power circuit includes the battery, battery cables, solenoid, and starter motor.
The parts of a typical starter include the main field housing, commutator-end (or brush-end) housing, drive-end housing, brushes, armature, and starter drive.

40. REVIEW QUESTIONS
What parts are included in the starter control circuit?
List the parts of a typical starter.
Explain why a gear-reduction unit reduces the amount of current required by the starter motor.
Describe the symptoms of a defective starter drive.

41. CHAPTER QUIZ Starter motors operate on the principle that _____.
The field coils rotate in the opposite direction from the armature
Opposite magnetic poles repel
Like magnetic poles repel
The armature rotates from a strong magnetic field toward a weaker magnetic field

42. CHAPTER QUIZ Starter motors operate on the principle that _____.
The field coils rotate in the opposite direction from the armature
Opposite magnetic poles repel
Like magnetic poles repel
The armature rotates from a strong magnetic field toward a weaker magnetic field

43. CHAPTER QUIZ 2. Series-wound electric motors _____.
Produce electrical power
Produce maximum power at 0 RPM
Produce maximum power at high RPM
Use a shunt coil

44. CHAPTER QUIZ 2. Series-wound electric motors _____.
Produce electrical power
Produce maximum power at 0 RPM
Produce maximum power at high RPM
Use a shunt coil

45. CHAPTER QUIZ
3. Technician A says that a defective solenoid can cause a starter whine. Technician B says that a defective starter drive can cause a starter whining noise. Which technician is correct?
Technician A only
Technician B only
Both Technicians A and B
Neither Technician A nor B

46. CHAPTER QUIZ
3. Technician A says that a defective solenoid can cause a starter whine. Technician B says that a defective starter drive can cause a starter whining noise. Which technician is correct?
Technician A only
Technician B only
Both Technicians A and B
Neither Technician A nor B

47. CHAPTER QUIZ 4. The neutral safety switch is located _____.
Between the starter solenoid and the starter motor
Inside the ignition switch itself
Between the ignition switch and the starter solenoid
In the battery cable between the battery and the starter solenoid

48. CHAPTER QUIZ 4. The neutral safety switch is located _____.
Between the starter solenoid and the starter motor
Inside the ignition switch itself
Between the ignition switch and the starter solenoid
In the battery cable between the battery and the starter solenoid

49. CHAPTER QUIZ
5. The brushes are used to transfer electrical power between _____.
Field coils and the armature
The commutator segments
The solenoid and the field coils
The armature and the solenoid

50. CHAPTER QUIZ
5. The brushes are used to transfer electrical power between _____.
Field coils and the armature
The commutator segments
The solenoid and the field coils
The armature and the solenoid

51. CHAPTER QUIZ 6. The faster a starter motor rotates _____.
The more current it draws from the battery
The less CEMF is generated
The less current it draws from the battery
The greater the amount of torque produced

52. CHAPTER QUIZ 6. The faster a starter motor rotates _____.
The more current it draws from the battery
The less CEMF is generated
The less current it draws from the battery
The greater the amount of torque produced

53. CHAPTER QUIZ 7. Normal cranking speed of the engine is about _____.
2000 RPM
1500 RPM
1000 RPM
200 RPM

54. CHAPTER QUIZ 7. Normal cranking speed of the engine is about _____.
2000 RPM
1500 RPM
1000 RPM
200 RPM

55. CHAPTER QUIZ
8. A starter motor rotates about _____ times faster than the engine. 18 10 5 2

56. CHAPTER QUIZ
8. A starter motor rotates about _____ times faster than the engine. 18 10 5 2

57. CHAPTER QUIZ
9. Permanent magnets are commonly used for what part of the starter?
Armature
Solenoid
Field coils
Commutator

58. CHAPTER QUIZ
9. Permanent magnets are commonly used for what part of the starter?
Armature
Solenoid
Field coils
Commutator

59. CHAPTER QUIZ
10. What unit contains a hold-in winding and a pull-in winding?
Field coil
Starter solenoid
Armature
Ignition switch

60. CHAPTER QUIZ
10. What unit contains a hold-in winding and a pull-in winding?
Field coil
Starter solenoid
Armature
Ignition switch

61. END