Download Ignition Systems File - Totton College

Ignition
Spark plugs 1
•
Construction
Electrodes
Spark plugs 2
Cold
Dimensions
Heat range
Hot
Ignition systems 1
Ignition coil
Distributor
Ignition systems 2
•Conventional ignition system
•
Electronic ignition 1
Hall effect
OPUS
Electronic ignition 2
•
Distributorless ignition system
Wasted spark
Ignition timing and torque
Turning effort created by
downwards pressure
Why the spark occurs
before TDC
Electronic Ignition (EI) Systems
Topics covered in this presentation:
 DIS Primary and Secondary Circuits
 Typical Distributorless Ignition Systems
 Direct Ignition and Capacitor Discharge Systems
EI / DIS Systems
Ignition systems were improved to
minimize exhaust emissions.
The distributor was replaced with an electronic system to
determine which spark plug should receive a spark.
Known as Electronic (EI) or Distributorless (DIS) Ignition systems.
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Typical DIS System Components
The components of a typical DIS system are:
 Ignition module.
 Ignition coils.
 Crankshaft sensor.
 Trigger wheel.
The advantages of a DIS system are:
 Fewer moving parts.
 No mechanical timing.
 Less maintenance.
 No mechanical load on engine.
 Increased coil saturation.
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Question 1
Which of the following is NOT an advantage of a EI system?
A) Fewer moving parts
B) Cheaper to produce
C) No mechanical load on engine
D) Less maintenance required
DIS Secondary Circuit
A spark plug is attached to each
end of secondary winding.
The two plugs are in cylinders whose
pistons reach top dead centre (TDC) at
the same time, but on different strokes.
The compression stroke
cylinder is the "event" cylinder.
The exhaust stroke cylinder
is the "waste" cylinder.
The cylinder head acts as a conductor
to complete the secondary circuit.
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Question 2
What is the compression stroke cylinder called when it is fired by the
DIS secondary circuit?
A) Event cylinder
B) Home cylinder
C) Waste cylinder
D) Lead cylinder
‘Waste Spark’
A voltage is produced across both
spark plugs at the same time.
The compression stroke spark
ignites the air and fuel mixture.
The exhaust stroke spark is
'wasted’ and has no affect on
engine operation.
The theoretical output voltages
should be equal in magnitude, but
of opposite polarity. In practice, the
waste spark voltage is smaller (the
reason why is covered later).
One plug fires using a positive
voltage, the other fires using a
negative voltage.
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DIS Primary Circuit
Primary winding connected
between 12V and ECU output.
Crankshaft sensor
Other sensors
Output on, current flows in primary
winding, building up magnetic field.
Spark required, output off,
magnetic field collapses, producing
very high secondary voltages.
As both plugs fire, system does not
need a method of determining which
plug requires a spark, it just needs
to know ‘when’ (crankshaft sensor).
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Question 3
In an EI system, what directly causes the secondary circuit to fire?
A) The crankshaft rotation
B) The induction coil switching on
C) Switching the power supply on
D) The ECU turning the primary winding off
DIS Voltage Waveforms
The diagram
shows primary
and secondary
coil voltages.
Typically, the event
spark = 20000V.
Typically, the waste
spark = 1000V.
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Typical Ford Distributorless Ignition System
This system has a coil for
each pair of spark plugs.
The ICM fires two spark plugs
at once, on the compression
and exhaust strokes.
The ICM is mounted
on a bulkhead, away
from coil pack.
It adjusts ignition timing by
monitoring engine speed,
load and temperature.
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Question 4
How many coils will there be in a typical Ford 4 cylinder system?
Enter your answer and press SEND.
Question 5
In a 4 cylinder system, how many times will the crankshaft turn before
the same event cylinder fires again as an event cylinder?
Enter your answer and press SEND.
Typical GM Distributorless Ignition System
This system uses an
ECU and an electronic
coil module (ECM).
The ECU monitors
sensors and sends
timing pulses to
the ECM.
When the ECM
receives correct signals
from crank / cam
sensors and the ECU, it
fires the appropriate
ignition coil.
The camshaft sensor replaces
the function of the distributor
cap and rotor arm.
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Question 6
In a typical GM distributorless ignition system, where does the
camshaft sensor send its signal?
A) To the crankshaft sensor
B) To the electronic control unit
C) To the electronic coil module
D) To the ignition coil
Direct Ignition Systems
System uses one ignition coil per spark plug.
Coils are mounted directly on top of spark plugs.
A ‘cassette’ assembly can be used to house multiple coils.
Coil
Advantages:
 No spark plug leads, therefore no RFI.
 No mechanical wear due to moving parts.
 Compact packaging.
Spark
plug
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Direct Ignition System Operation
This system is wired so that two coils
are switched by one ECU output.
It functions using the
‘waste spark’ principle.
The ECU controls ignition
timing using crankshaft and
other sensor information.
This system is wired so that coils are
switched by individual ECU outputs.
The ECU has to know the
position of cylinder 1.
It controls ignition timing using camshaft,
crankshaft and other sensor information.
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Question 7
How many coils will there be in a six cylinder direct ignition system?
Enter your answer and press SEND.
Capacitor Discharge Ignition (CDI) Systems
Widely used in racing for high RPM operation.
Uses a capacitor to store energy
that is discharged through a coil,
at the required firing time.
Discharge time = 150 - 500μs.
Modern CDI systems produce multiple
sparks to overcome poor combustion
problems with lean mixtures.
CDI module and coil
Saab have fitted CDI as part of
their direct ignition system.
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Typical CDI (DIS) System Operation
Power supply
converts 12V DC
into 400V, to
charge the
capacitor.
When a spark is
required, the
capacitor is
discharged
through a
primary winding.
This produces a high
voltage pulse across
a secondary winding
(typically 50,000V).
Charging and discharging timing is controlled by the computer.
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Question 8
Where does the capacitor discharge to in order to produce a
spark in a typical CDI system?
A) To the secondary winding
B) To the primary winding
C) To the relay
D) To the spark plug
Summary
You should now be aware of:
 DIS Primary and Secondary Circuits
 Typical Distributorless Ignition Systems
 Direct Ignition and Capacitor
Discharge Systems
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Self Diagnosis and Trouble Codes
Topics covered in this presentation:
OBD and EOBD systems
Fault Code Types, Retrieval and Display
Scan Tools
On-board Diagnostics (OBD)
Modern vehicles have complex computers to control systems.
Diagnostic systems developed to help technician diagnose faults.
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Types of On-board Diagnostic (OBD)
Early OBD systems detect out-of-range sensors and actuators and store a
diagnostic trouble code when a fault occurs.
EOBD also monitors systems to
detect potential problems
before they occur.
Diagnostic monitors run at
specified time intervals to check
vehicle operation.
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Question 1
Which of the following is a major difference between ODB and EODB
systems?
A) EODB gets the data faster
B) EODB can detect potential problems
C) EODB ONLY runs at specified time intervals
D) EODB does not detect out of range sensors and actuators
Malfunction Indicator Lamp
Dashboard mounted malfunction
indicator lamp (MIL) indicates
presence of fault.
MIL
(CHECK ENGINE)
On OBD systems, MIL illuminates if
fault occurs.
On EOBD systems, MIL also illuminates if
emission limits are going to be
exceeded.
Continuous illuminated MIL
represents non-critical fault.
Flashing MIL represents critical fault.
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Question 2
How does an EODB system warn of a critical fault?
A) It turns off the engine
B) It sounds a warning buzzer
C) It flashes a warning light
D) It illuminates a warning light
Question 3
Where on an EOBD system, would a malfunction indicator lamp normally
be mounted?
A) On the ECU
B) In the engine compartment
C) Near the fusebox
D) On the dashboard
Diagnostic Trouble Code (DTC) Retrieval
OBD DTC retrieval methods are
manufacturer dependent.
DTCs may be accessed via data link
connector (DLC), triggered by ECU
switch, or by pressing buttons.
Wire link
DLC
DTCs may be displayed by:
MIL lamp.
Analogue voltmeter.
MIL lamp
Light emitting diodes (LEDs) on an ECU.
Some OBD and all EOBD DTCs can be
retrieved by using a scan tool.
Analogue voltmeter
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Scan Tool
Scan tool accesses and retrieves stored
trouble codes.
On OBD systems, scan tool retrieves, displays
and clears codes, via DLC.
On EOBD systems, scan tool also displays ‘live’ data
and engine condition ‘snap shots’.
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Cartridges
Most scan tools use plugin cartridges.
Cartridges contain data that
is manufacturer(s) specific,
for example:
Ford Cartridge.
GM Cartridge.
US Domestic Cartridge (Ford, GM,
Chrysler, Jeep).
Cartridges can be updated as
vehicles change.
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Question 4
Scan tools use plug in cartridges that are vehicle specific. Is this
true or false?
Answer True or False.
Connecting the Scan Tool
Scan tool connects to DLC or diagnostic connector.
OBD DLC may be under dashboard or hood.
EOBD diagnostic connector has to be in passenger compartment.
EOBD has standard 16 pin
diagnostic connector.
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Question 5
An EOBD scan tool diagnostic connector will be found in the passenger
compartment. Is this true or false?
Answer True or False.
Using the Scan Tool
Consult handbook before using scan
tool. Easy to operate, with on-screen
instructions.
May require vehicle identification
number (VIN) code for vehicle
information.
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Using the Scan Tool
Capable of many functions:
Circuit and sensor information.
Fault description.
Run tests.
Record of failures from start up.
Help to rectify problems.
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Trouble Code ID
OBD systems have 3 or 5 digit codes.
EOBD systems have standardized codes.
EOBD codes conform to the format below:
P 0 1 1 6 = Engine coolant temperature circuit range problem.
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Question 6
How many letters and numbers will be found in a standard EOBD trouble code?
Enter your answer and press SEND.
Diagnosis - Example Procedure
Ensure scan tool has correct cartridge.
Connect scan tool to vehicle.
Switch on ignition.
Enter vehicle details.
Retrieve information from ECU.
Correctly diagnose and repair
fault.
Ensure stored codes are cleared.
Road test vehicle, ensure fault has been corrected (check
for fault codes).
Disconnect scan tool.
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Diagnosis - Wiggle Test
Corroded, loose or dirty connections cause hard to find faults.
Wiggle connection to see if intermittent change displayed on scan tool.
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Summary
You should be aware of:
OBD and EOBD systems
Fault Code Types, Retrieval and Display
Scan Tools
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