Ignition System

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

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

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

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

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

Parts Battery Ignition switch Bypass circuit Resistance circuit Primary circuit

Parts Secondary circuit Ignition coil Spark plugs Ignition system wires

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

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

Primary circuit Low voltage Does not exceed 12.5 volts Conventional wires

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

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

Resistance circuit A resistor or resistor wire that makes sure the system can not exceed 9.5 10.5 Volts

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

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

Spark plug wires Cary high voltage from distributor to spark plugs 1000 -4000 ohms resistance per foot

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

Ignition coil A transformer Creates short bursts of high voltage

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

Ignition coil Newer vehicles Leaner fuel mixture Larger spark plug gap Voltage ranges from 4000 – 30 000 volts Average of 15 000 volts

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

Primary Windings Several hundred turns of heavy gage wire

Secondary windings Several thousand turns of light gauge wire

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

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

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