Unit A51: Operation and Testing of Vehicle Electronic Ignition Systems

Pearson BTEC Level 3 AME (Development Technical Knowledge)

Unit A51 Introduction
Electronic ignition systems have developed in line with the advancement of engine technology and engine management systems. Modern electronic ignition systems have improved vehicle reliability, performance and efficiency of operation. Recent advances in spark plug design, manufacture, operation and longer working life have also improved electronic ignition systems. It is important that all motor vehicle technicians are aware of these systems and are able to recognise and confirm faults. This unit will enable learners to understand the fundamental operating principles of electronic ignition systems and will give them the knowledge and understanding needed to carry out accurate diagnosis and repair. Learners will develop an understanding of the main components of vehicle electronic ignition systems and their relationship to the efficient operation of the engine unit and sub-systems. Note that the use of ‘e.g. ’ in the content is to give an indication and illustration of the breadth and depth of the area or topic. As such, not all content that follows an ‘e.g. ’ needs to be taught or assessed.

Unit content
1 Understand the function and operation of conventional ignition systems
and their components

Ignition system operation: ignition timing (static and dynamic); dwell (angle, time, variation); ignition scope patterns, e.g. spark kV, primary circuit, secondary circuit, dwell, coil output
Ignition system components: circuits (diagrams, primary, secondary); contact breaker; coil; leads; distributor and cap; rotor arm; spark plugs; mechanisms (mechanical advance, retard, vacuum advance)
2 Understand the operation of programmed electronic ignition and
distributorless ignition system
Programmed electronic ignition: components, functions and operation;
electronic control unit; sensors, e.g. manifold absolute pressure, crankshaft,
camshaft, engine temperature, knock, air temperature; ignition coil; distributor; ignition switch; reluctor disc; discharge, e.g. capacitor, inductive
Distributorless ignition system: components, functions and operation;
transformer; capacitor; ignition coil(s), e.g. waste spark, direct acting; spark
plug; sensor, e.g. manifold pressure, crankshaft, camshaft, knock; primary
current switching modules, waste spark, direct acting
3 Know about the function and operation of pulse generators and control

Generators: Hall effect, e.g. Hall voltage, Hall integrated circuit (IC), vanes,
magnet, control module; inductive pick-up, e.g. permanent magnet, inductive windings, trigger wheel; optical pulse, e.g. light-emitting diode (LED), phototransistor
Transistor assisted contacts: transistor operation; Darlington pair; advantages of breakerless systems
Control modules: e.g. pulse shaping, dwell period control, voltage stabilisation, primary switching, pulse processing, secondary output control, ignition amplifier, air gap, electronic spark advance, spark advance map, read-only memory (ROM), erasable programmable read-only memory (EPROM), knock control
4 Be able to undertake tests on electronic ignition system to verify
system faults

Testing: equipment, e.g. on-board diagnostics (OBD), test instruments, voltage drop tester, electronic control unit tester; spark advance and retard tester; safe working practice; components and circuits, e.g. fuses, wiring, connectors, coil, spark plug, leads, rotor arm, distributor cap, pulse generator, sensors (such as crankshaft, camshaft, knock), break out box, ignition switch, reluctor air gap; checking for faults, e.g. moisture, dirt, corrosion, fault code reading, gap, data link connection, output and resistance, spark plug leads condition and resistance, rotor arm condition and leakage, distributor cap condition and leakage, dwell angle, spark plug condition, pulse generator module resistance, ignition timing, sensor output, sensor operation