1. Starting and Motor Systems
Chapter 18
Starting and
Motor Systems

2. Types of Electric Motors
Electric motors are used to start the engine
In hybrid electric vehicles (HEVs), electric motors can used to propel the vehicle
Smaller electric motors are DC
Traction or drive motors are AC

3. Basics of Electromagnetism

4. Electromagnets Natural magnets from magnetite
Artificial magnets rearrange molecules to align along North and South poles
Artificial magnets can be temporary or permanent
Current carrying wire generates a magnetic field

6. Coils

7. Magnetic Circuits and Reluctance
Lines of flux can only occupy a closed magnetic circuit
The resistance to the passage of flux lines is called reluctance
Inserting an iron core into a coil increases the strength of the magnetic field

9. Magnetic Circuits and Reluctance (Cont.)
Electromagnetic field is directly proportional to the number of turns and current flow
The number of magnetic lines is proportional to the ampere-turns divided by the reluctance

10. Magnetic Field Strength
Magnetic polarity depends on the direction of current flow
Field strength increases if current increases
Field strength increases if coil turns increase
If reluctance increases, field strength decreases

11. Motors Convert electric energy into mechanical energy
Use interactions of magnetic fields
An electromagnet is fitted to a shaft
Shaft surrounded by stationary fields
Polarity of fields are switched
Shaft rotation can do work

12. Basic Motor

13. Starting Motors Great amounts of torque for short periods
All starting motors of same basic design
Housing or frame contains internal parts
Field coils produce strong stationary fields
Polarity switching fields from rotating armature
Brushes and commutator switch polarity
End frame supports armature

14. Housing

15. Field Coils

16. Armature

17. Brushes and End Frame

18. Knowledge Check
Describe the basic operating principles of a DC electric motor.
The interaction between stationary magnetic fields and magnetic fields around the armature cause the armature to spin. The fields generated around the armature switch polarity to keep the interaction with the stationary fields attracting and repelling to keep the rotation going.

19. Operating Principles

20. Operating Principles (Cont.)
Many armature segments are used
The number of coils and brushes differ between models
Three styles of motor windings:
Series motors
Parallel or shunt motors
Compound or combination motors

22. Operating Principles (Cont.)
Series motors develop maximum torque at start-up
Shunt motors develop less start-up torque but maintain constant speed under load
Compound motors have good starting torque with constant speed
Shunt coils are used to limit free speed

23. Permanent Magnet Motors
Replaces field coils with permanent magnets
Current supplied directly to armature
Function same as other motor designs
Use planetary gear assembly for gear reduction
Gear reduction increases torque

25. Gear Reduction Starter

26. Counter EMF Starter motor torque dependant on: Current draw
The slower the armature turns the more current it will draw
More torque needed to crank a difficult engine

27. Counter EMF (Cont.)
CEMF is produced when armature loops pass through magnetic fields
This voltage opposes battery supplied voltage
The faster the spin, the more voltage is induced

28. Brushless Motors Removes brush contacts and wear
Use permanent magnet motor and electromagnet field windings
Used in some HEVs

29. Starting System
Turns the crank until the engine can operate under its own power
Starter motor engages and spins flywheel
Only purpose is to crank engine fast enough to start

30. Starting System Components
Battery
Ignition switch
Cable and wires
Starter solenoid or relay
Starter motor
Starter safety switch

31. Typical Starting System

32. Starter Circuit Carries the high current flow within the system
Supplies power for engine cranking
Components are:
Battery and battery cables
Magnetic switch or solenoid
Starter motor

33. Battery and Cables
Starter circuit requires two or more heavy-gauge cables
Negative cable connects to engine or transmission
Positive cable connects to starter solenoid or relay

34. Magnetic Switches
Enables control circuit to open and close starter circuit
Can be either a solenoid or a relay:
Solenoid is most common
Relays is similar to a solenoid but does not mesh starter drive gear with flywheel

35. Solenoids Meshes drive gear with flywheel
Energizes starter motor through contacts

36. Starter Relay Used as an electrical relay to the starter
Provides an alternate electrical path for ignition coil during cranking
Some vehicles use both a relay and a starter solenoid to reduce current through the ignition switch

37. Ford Starter Relay

38. Knowledge Check What are the functions of the starter solenoid?
The solenoid connects the battery to the starter motor and engages the drive gear with the flywheel.

39. Starter Drives Meshes armature to flywheel
Pinion meshes with flywheel before the armature spins
An overrunning clutch is used to prevent starter damage when the engine starts

40. Pinion gear is locked to the armature shaft in one direction

41. Pinion freewheels when turned opposite drive direction by the flywheel

42. Gear Reduction Drives

43. Control Circuit
Allows a small amount of current to control the high current starter circuit
Consists of ignition switch, safety switch, and starter solenoid or relay
Starting safety switch
Prevents vehicle from starting unless in park or neutral or with clutch disengaged

45. Starting Safety Switch
Neutral safety or clutch safety switch
Prevents starter operation if transmission is not in Park or Neutral of if clutch pedal is not fully depressed

46. Starting System Testing
Do not crank the engine for longer than 15 seconds
Allow at least two minutes in between cranking cycles for starter to cool

47. Preliminary Checks Check the battery and charge as needed
Check wiring and cable connections
Check to make sure the cables are the correct size
Check any fusible links in the wiring
Ensure engine has correct weight oil

48. Preliminary Checks (Cont.)

49. Safety Precautions Starting tests performed with engine cranking
Bypass ignition to prevent engine from starting
Make sure transmission is out of gear and parking brake is set

50. No-Crank Problems Verify battery and cable condition.
Test for voltage at solenoid S terminal
May need to connect scan tool to check starter circuit signal and anti-theft system

51. Starter Solenoid Problems
Typical complaint is a clicking noise when attempting to start the engine
Anything that reduces current flow will affect solenoid operation
Solenoids can often be replaced separately or as a starter assembly

52. Starting Safety Switches
Can be checked with a voltmeter or ohmmeter
With transmission in park or clutch depressed, switch should be closed
May need adjusted if not closing circuit

53. Battery Load Test
Slow cranking is often caused by insufficient battery current
The battery must be able to crank engine under all load conditions

54. Cranking Tests
Cranking voltage test measures available voltage during cranking
Refer to service manual for voltage specifications, normally at least 9.6 volts
Cranking current test measures starter current draw during cranking
Watch voltage and amperage and compare to specifications

56. Insulated Circuit Resistance Tests
Insulated circuit contains all high current cables and connections
Disable or bypass the ignition
Typical reading specifications volts
Higher readings indicated resistance in either the insulated positive or negative circuits

58. Starter Relay Bypass Test
Simple way to determine if relay is operational
Disable the ignition
Connect a heavy jumper between the battery positive terminal and relay’s starter terminal

59. Control Circuit Voltage Drop
High resistance in solenoid switch circuit reduces current flow through solenoid windings
Disable the ignition system
Test between battery positive and starter switch terminal on solenoid or relay
Normally less than 0.5 volts

60. Control Circuit Voltage Drop (Cont.)

61. Starter Drive Test Checks for a slipping starter drive
Bypass or disable the ignition
Crank engine for several seconds
Repeat at least three times
If engine stops cranking but starter is still spinning, the starter drive is slipping

62. Knowledge Check
Technician A says a faulty Park/Neutral switch can cause a no-crank complaint. Technician B says a poor battery cable connection can cause a no-crank condition. Who is correct?
Both Technicians A and B

63. Removing the Starter Motor
Disconnect battery negative cable
Disconnect solenoid wiring and mark as necessary
Loosen starter mounting bolts
Support the starter and remove bolts
Lift starter away from flywheel

64. Free Speed (No-Load) Test
Every starter should be bench tested when removed and before being installed
Firmly clamp starter in a vice
Connect ammeter to battery cable and starter to a battery
Check current draw and motor speed

65. No-Load Testing

66. Starter Motor Service Field coil tests Refer to a wiring diagram
Check for opens and shorts in coil feeds

67. Starter Motor Service (Cont.)
Armature tests
Inspect commutator
Check for continuity between commutator segments

68. Starter Motor Service (Cont.)
Brush inspection
Ohm check brush holder
Measure brush length
Bearings and bushings
Check for loose, tight, or rough bearings and bushings

69. Starter Motor Service (Cont.)
Starter drives and clutches
Inspect teeth on drive gear
Check flywheel teeth
Check operation of overrunning clutch

70. Starter Motor Reassembly
Reverse disassembly procedures
Lubricate splines on armature shaft that the drive gear rides on
Lubricate bearings and/or bushings with high-temperature grease
Apply sealant to solenoid flange
Check pinion depth clearance
Perform a no-load bench test

71. Installation Sand paint from mounting point
Check starter clearance on starters that use shims