1. Ignition System

2. Purpose
Distribute high voltage pulses to spark plugs in correct sequence.

3. Basic operation Ignition switch on Switching device closed
Piston moves close to TDC
Ignition trigger device opens
Ignition coil charges

4. Basic operation Current stops going to ignition coil
Lack of current causes a high voltage surge, ignition coil discharges

5. Basic operation Surge flows across spark plug gap, creating an arc
Arc ignites air/fuel mixture

6. Basic operation Ignition trigger device closes, recharging coil
Electricity flows to the coil
High voltage surge stops

7. Parts Battery Ignition switch Bypass circuit Resistance circuit
Primary circuit

8. Parts Secondary circuit Ignition coil Spark plugs
Ignition system wires

10. Battery-Supply voltage
Battery supplies voltage at start up
Battery and alternator supply voltage during operation

13. Ignition switch
Hot Switch, one side is connected to the battery and the other side is connected to the ignition system

15. Primary circuit Low voltage Does not exceed 12.5 volts
Conventional wires

16. Secondary circuit High Voltage 4000 – 30 000 volts
Heavy wire that prevents electrical leakage

17. Bypass circuit Makes sure there is enough voltage for start up
Starts engine using a lot of voltage

18. Resistance circuit
A resistor or resistor wire that makes sure the system can not exceed Volts

19. Resistance circuit
Newer computer control cars have computer controlled voltage regulators
Resistor circuit not needed today

20. Distributor Sends voltage to appropriate spark plugs
Tells magnetic field inside of coil when to collapse

21. Spark plug wires Cary high voltage from distributor to spark plugs
ohms resistance per foot

23. Spark plugs Provide a spark for ignition
Is a ground for primary circuit
Insulated to stop electrical leakage

25. Ignition coil
A transformer
Creates short bursts of high voltage

27. Ignition coil Older vehicles Small spark plug gaps
Less voltage 4000 – 8000 volts

28. Ignition coil Newer vehicles Leaner fuel mixture Larger spark plug gap
Voltage ranges from 4000 – volts
Average of volts

29. Ignition coil parts 2 sets of windings
2 Primary terminals (low voltage)
Iron core inside of windings
1 High voltage out put connection

30. Primary Windings
Several hundred turns of heavy gage wire

31. Secondary windings
Several thousand turns of light gauge wire

32. Ignition coil operation
Current from the battery flows through the secondary windings, creating a magnetic field.

33. Ignition coil operation
When current flow is interrupted the magnetic field collapses And sends its current through the secondary windings.

34. Ignition coil operation
Because of the high number of secondary windings voltage is increased and current is decreased