Ignition

Spark plugs 1 Construction Electrodes Tutor notes Ask learners the purpose of spark plugs and roughly how many volts are required to make electricity jump the gap. Confirmation: to initiate combustion, around 8,000 volts. Explain how electrode shape affects the spark produced. Construction Electrodes

Spark plugs 2 Cold Hot Dimensions Heat range Tutor notes Describe the dimensions used in spark plug design and the differences between hot and cold running spark plugs. Dimensions Heat range

Ignition systems 1 Ignition coil Distributor Tutor notes Describe the process of the ignition coil, used as a step-up transformer. Show how mutual inductance is able to take battery voltage and turn it into many thousands of volts. Ask learners the purpose of the distributor. Confirmation: to distribute the high-tension electricity to the correct spark plug in the correct order. Ignition coil Distributor

Ignition systems 2 Conventional ignition system Tutor notes Show how a conventional ignition system is able to switch the primary circuit of the ignition coil using contact breakers.

Electronic ignition 1 Hall effect OPUS Tutor notes Describe the process of other types of electronic ignition systems to include Hall effect and optical pickup system (OPUS). Hall effect OPUS

Electronic ignition 2 Distributorless ignition system Tutor notes Also describe the process of the distributorless ignition system (DIS).

Wasted spark Tutor notes Describe the process of wasted spark ignition systems: Wasted spark works on the principle that if a spark is provided to both companion cylinders at the same time, the one which is on its compression stroke will ignite the fuel and start the power stroke while the one on the exhaust stroke will be wasted. The next time around, after 360 degrees of crankshaft revolution, the other cylinder will be on its compression stroke and ignite the air/fuel mixture, while the companion cylinder will be on its exhaust stroke and the spark will be wasted. State how two companion spark plugs are operated at the same time, with one on the compression stroke and one on the exhaust stroke. The spark on the compression stroke will be the ‘event spark’. The spark on the exhaust stroke will be the ‘wasted spark’. Show how the cylinder head completes the circuit: giving one spark plug a positive spark and one spark plug a negative spark.

Ignition timing and torque Tutor notes Explain the process of ignition timing. Describe how the spark has to occur before top dead centre so that pressure build-up occurs on the piston crown at approximately 10 degrees after top dead centre. If the spark occurs too early (advanced), engine turning effort may be lost due to lack of leverage through the connecting rod. If the spark occurs too late (retarded), engine turning effort may be lost as the maximum leverage is passed. If possible, show learners timing marks using a strobe light. Ensure that none of your learners have light-sensitive epilepsy. 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. Next >

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. Next >

Question 1 Which of the following is NOT an advantage of a EI system? A) Fewer moving parts B) Cheaper to produce Correct Answer = B 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. Next >

Question 2 What is the compression stroke cylinder called when it is fired by the DIS secondary circuit? A) Event cylinder B) Home cylinder Correct Answer = A 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. Next >

DIS Primary Circuit Crankshaft sensor Other sensors Primary winding connected between 12V and ECU output. 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). Next >

Question 3 In an EI system, what directly causes the secondary circuit to fire? A) The crankshaft rotation B) The induction coil switching on Correct Answer = D 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. Next >

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. Next >

Question 4 How many coils will there be in a typical Ford 4 cylinder system? Enter your answer and press SEND. Correct Answer = 2

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. Correct Answer = 2

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. Next >

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 Correct Answer = C 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. Spark plug Coil Advantages: No spark plug leads, therefore no RFI. No mechanical wear due to moving parts. Compact packaging. Next >

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. Next >

Question 7 How many coils will there be in a six cylinder direct ignition system? Enter your answer and press SEND. Correct Answer = 6

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. CDI module and coil Discharge time = 150 - 500μs. Modern CDI systems produce multiple sparks to overcome poor combustion problems with lean mixtures. Saab have fitted CDI as part of their direct ignition system. Next >

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. Next >

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 Correct Answer = B 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 End >

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. Next >

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. Next >

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 Correct Answer = B 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. Next >

Question 2 How does an EODB system warn of a critical fault? A) It turns off the engine B) It sounds a warning buzzer Correct Answer = C 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 Correct Answer = D C) Near the fusebox D) On the dashboard

Diagnostic Trouble Code (DTC) Retrieval OBD DTC retrieval methods are manufacturer dependent. Wire link DLC DTCs may be accessed via data link connector (DLC), triggered by ECU switch, or by pressing buttons. MIL lamp DTCs may be displayed by: MIL lamp. Analogue voltmeter. Analogue voltmeter Light emitting diodes (LEDs) on an ECU. Some OBD and all EOBD DTCs can be retrieved by using a scan tool. Next >

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’. Next >

Cartridges Most scan tools use plug-in 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. Next >

Question 4 Scan tools use plug in cartridges that are vehicle specific. Is this true or false? Answer True or False. Correct Answer = F

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. Next >

Question 5 An EOBD scan tool diagnostic connector will be found in the passenger compartment. Is this true or false? Answer True or False. Correct Answer = T

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. Next >

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. Next >

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. Next >

Question 6 How many letters and numbers will be found in a standard EOBD trouble code? Enter your answer and press SEND. Correct Answer = 5

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. Next >

Diagnosis - Wiggle Test Corroded, loose or dirty connections cause hard to find faults. Wiggle connection to see if intermittent change displayed on scan tool. Next >

Summary You should be aware of: OBD and EOBD systems Fault Code Types, Retrieval and Display Scan Tools End >