IGNITION SYSTEMS
What is Ignition System ???
The system in an internal-combustion
engine that produces the spark
to ignite the mixture of fuel and air:
includes the battery, ignition coil,
distributor, spark plugs, and associated
switches and wiring.
IGNITION FUNCTION
Produces 30,000 volt spark across spark plug
Distributes high voltage spark to each spark plug in
correct sequence
Times the spark so it occurs as piston is nearing top dead
center
Varies spark timing with load, speed, and other conditions
BASIC IGNITION SYSTEM
COMPONENTS
BATTERY
IGNITION SWITCH
IGNITION COIL
SWITCHING DEVICE
SPARK PLUG
IGNITION SYSTEM WIRES
BASIC IGNITION SYSTEM
Battery supplies power to
entire system
Ignition Switch turns
engine on or off
Coil transforms volts
Switching device triggers
ignition coil
Spark Plug and wires
distribute spark
IGNITION COIL
Transformer
2 sets of windings
Primary windings
Secondary windings
Iron core
Produces magnetic
field
IGNITION SYSTEM TYPES
Battery ignition system
Magneto ignition system
Distributor less ignition system
BATTERY IGNITION SYSTEM
A battery ignition system has a 6- or 12-volt battery
charged by an engine-driven generator to supply
electricity, an ignition coil to increase the voltage, a
device to interrupt current from the coil, a distributor to
direct current to the correct cylinder, and a spark plug
projecting into each cylinder.
Current goes from the battery through the primary
winding of the coil, through the interrupting device, and
back to the battery.
The primary circuit consist of the battery, ammeter, ignition
switch, primary coil winding, capacitor, and breaker points.
The function of these components are :
Battery – Provides the power to run the system
Ignition switch – allows the driver to turn the system on
and off
Primary coil – produces the magnetic field to create the
high voltage in the secondary coil.
Breaker points – a mechanical switch that acts as the
triggering mechanism
Capacitor – protects the points from burning out.
The Secondary circuit converts magnetic induction into high
voltage electricity to jump across the spark plug gap, firing
the mixture at the right time. The function of the components
are –
secondary coil – the part of the coil that creats the high
voltage electricity.
Rotor – spin around on the top of the distributor shaft, and
distributes the spark to the right spark plug.
spark plug – Take the electricity from the wires and give it
an air gap in the combustion chamber to jump across to light
the mixture.
MAGNETO IGNITION SYSTEM
The simplest form of spark ignition is that using
a magneto.
An ignition magneto, or high tension magneto, is
a magneto that provides current for the ignition system of
a spark-ignition engine, such as a petrol engine.
The engine spins a magnet inside a coil, or, in the earlier
designs, a coil inside a fixed magnet, and also operates
a contact breaker, interrupting the current and causing the
voltage to be increased sufficiently to jump a small gap.
The spark plugs are connected directly from
the magneto output.
Rotor Arm
Magneto Unit
Spark Generation
Condenser
Power
Generation
Coil
Distribution
Contact
Magneto
Breaker
Ignition
Switch
IGNITION SYSTEM – Magneto System
Typical Vacuum Advance
Distributor
Diaphragm Adjustable
Vacuum Plate
Chamber
Cap
‘Points’
Body Inlet
Pressure Cam Adjuster
Centrifugal
Advance
Input
Shaft Centrifugal
Weights
IGNITION SYSTEM – Distributor
Cap Connector
Ceramic Body
Hexagon
Outer Casing
Copper Sealing Gasket
Securing Thread
Gap
Outer
Electrode
IGNITION SYSTEM – Spark Plug
Distributorless Ignition Systems
• Operation
• Developments
• Testing
Distributorless Ignition Systems
The principles of operation are basically no different than
those for distributor equipped electronic ignition systems that
began appearing on American automobiles in 1972.
There are 2 obvious differences:
• A DI system does not have a mechanical distributor.
• Most DI systems use one coil for every two spark plugs
(however some systems have one coil per cylinder i.e.
BMW).
Distributorless Ignition Systems
In operation the only major difference is that DI systems fire
all of the engines spark plugs in ONE crankshaft revolution,
whereas the old mechanical distributor type fires all plugs every
TWO crankshaft revolutions.
On all four stroke engines, equipped with or with out distributors
require TWO crankshaft revolutions (720° travel) for the
combustion to occur on each cylinder.
On engines with an even number of cylinders, combustion occurs
in half of the cylinders in the first revolution (360°) and in the
other half in the second half of the revolution. Each cylinder that
has combustion in the first revolution has a companion cylinder
that fires 360° apart from it during the second revolution.
Layout +
ECU
Primary
ECU
Secondary
Primary
Secondary
NGK
NGK NGK NGK
CONTACT POINT SYSTEM
Distributor turns 1/2
engine rpm
Distributor Cam
Contact Points
Condenser
Point Dwell (Cam
angle)
Basis for all Systems
IGNITION SYSTEM TROUBLESHOOTING
Problem Possible causes and/or solutions
No spark out of the coil Possible open in the ignition switch
circuit
Possible defective ignition module
(if electronic ignition coil)
Possible shorted condenser
Weak spark out of the coil Possible high-resistance coil wire or
spark plug wire
Possible poor ground between the
distributor or module and the
engine block
Engine missing Possible defective (open) spark plug
wire Possible
worn or fouled spark plugs
Possible defective pickup coil
Possible defective module
Possible poor electrical connections
at the pickup coil and/or module
