Ignition Systems And Starter Motors Flashcards
What is a typical ignition system composed of?
- Source of high voltage - usually two mags
- Distributer for each mag
- Connecting cables, between the distributors and the spark plugs, called high-tension leads
What is a magneto?
- Self-contained, engine-driven electrical generator that produces high voltage to ignite the fuel-air mixture in the combustion chamber.
- Operates independently of the electrical system
- Consists of a rotating magnet, 2 copper wire coils, breaker points, and a capacitor
- Directly geared to the engine - makes the magnet rotate at crankshaft speed within an iron core.
What is a distributor?
A rotating switch mechanically driven by the engine that receives the high tension current from the magneto and direct it to each of the cylinders .
- Geared to rotate at 1/2 the crankshaft speed.
- Situated in the magneto casing.
What are high tension leads?
Transfer the current from the distributor to each individual spark plugs.
What are spark plugs?
Deliver the electrical spark to ignite the fuel-air mixture in the combustion chamber.
- Creates a gap in the secondary circuit.
Includes:
- Centre electrode, ground electrode, and metal shell
What is spark plug fouling?
When a spark plug’s electrodes become covered with oil or carbon, it affects its ability to ignite the charge correctly.
- They often foul due to the mix of low engine temperatures and high led content.
How do you clear spark plug fouling?
Increase engine power to 2000RPM for 60 seconds.
What are impulse couplings?
A device that generates enough speed to create a spark on startup.
- Stores energy inside S soiled spring from the early phase of the magnetos rotation and releasing it slight later than the normal operation to create an acceleration.
Provides enough voltage to induce a spark.
- Only one mag, usually the left one, is fitted with an impulse coupling.
What is the ignition switch?
- OFF: Both mags are earthed via the p-leads
- R: Right mag is active and left is earthed
- L: Left mag is active and the right is earthed
- Both: Both mags are live (normal operation)
- Start: Activates the starter motor and grounds the right mag (without impulse coupling)
What does the insulator in a spark plug do?
Stops spark from deviating.
What does the metal shell in the spark plug do?
Provides ground connection to the engine block.
What does the central electrode do in a spark plug?
Conduct the electrical current from the ignition system to the ga between the centre and ground electrodes.
What is the ground electrode in the spark plugs?
Attached to a metal shell - serves as the return path for the electrical current and helps create the spark.
What is a magnetos check?
- To check if the mags are earthed.
- Live cut check - briefly turning the key switch to off - engine should start to fail.
If this does not happen, it is likely due to a faulty p-lead.
- Dead cut check - done in run ups
What is solid state ignition?
Used to reduce maintenance by removing all moving parts and contact breakers present in a magneto.
What is a solid state ignition composed of?
TDC sensor, RPM sensor, manifold pressure sensor, a coil pack, and an electronic control unit (ECU), external power source (battery).
Explain the operation of the SSI.
- Uses power from the battery to induce a high voltage current in the coil pack at the right time for each cylinder.
- Timing is achieved by receiving information from the RPM sensor, TDC sensor, and the manifold pressure sensor.
- Depending on the RPM, an SSI can retard or advance the spark for starting or for more efficient burn in the combustion chamber.
As RPM increases, the spark mist be advanced due to the time it takes for the combustion to reach its peak pressure.
What systems are used if the battery runs out of energy?
- Back-up battery - Is not charged by the engine.
- SSI directly connected to the generator
- Own power supply
What does a SSI integrity check do?
To verify the proper functioning of the ignition system components and detect any potential issues that may lead to engine performance degradation or failure.
