Air Fuel Ratio Meters
The ignition system of an internal combustion engine is an essential part of the overall engine system. It generates a spark or a very high voltage to ignite a fuel-air mixture in the engine's combustion chamber. The system also controls the timing of the spark/voltage to ensure it occurs at the right time and is sent to the correct cylinder. These systems are made of two circuits which work together to create an electric spark at the spark plugs. These circuits are:
The ignition circuits are made of various components designed to achieve specific functions on the system. These components are:
Battery – the battery provides electric power for the circuit.
Ignition switch – this component is normally mounted on the dashboard or steering column. It controls the current flowing through the battery and the ignition.
The ignition coil - the coil features a metal casing containing two sets of wires on a central iron core. This electromagnetic device converts battery voltage into high-tension current (30,000 volts and greater).
The distributor – this unit directs the flow of high-voltage current from the coil and sends it to each spark plug. It has a metal bowl that contains a central shaft which is often driven by the camshaft. The bowl houses the capacitor, distributor cap, contact-breaker points, and rotator arm.
Spark plugs – these devices provide an air gap in the combustion chamber for an electric arc. The high-tension current from the distributor flows through the spark plug then generates a spark as it passes through the air gap to the side electrode. The spark then flows through the spark plug body and the engine, then back to the coil, completing the circuit.
Automotive ignitions have evolved over the years to deliver improved and more powerful performance. Today, there are three main types of automotive ignitions and despite their differences in components and technology, they operate on the same basic principle.
Here's an overview of the three types of systems:
In this type of ignition, the distributor cam and shaft rotate when the ignition switch is turned on causing the distributor cam to close and open the contact points. Since contact points of this ignition are connected to the primary windings, they make and break the primary circuit. When the contact breakers are closed, the current produces a magnetic field in the coil's core. When the points open, the current stops flowing causing the magnetic fields generated in the coil to collapse. The change of magnetic flux produces a high voltage in the secondary windings that causes the gap in the spark plug to arc and ignite the fuel.
The biggest drawback of breaker-point systems is that they require regular maintenance to compensate for wear and tear.
The main difference between the breaker-point ignition and the electronic ignition is in the primary circuit. The primary circuit in a breaker-point system is open and closed by contact breakers while that of the electronic ignition is open and closed by an electronic ignition control module.
This type of system is maintenance-free as it doesn't have moving parts, has more power output and is more fuel efficient. Types of the electronic ignition include capacitance discharge ignition (CDI), piezo-electric ignition, the Texaco system, and transistorized system.
This type of system is common in modern engines. It doesn't have a distributor but instead has an ignition coil mounted on top of the spark plug. The timing of the spark plug is controlled directly by the engine control computer or by an ignition module.
The major components of the distributorless system are an electronic control module, a magnetic sensor, coil packs, and a crankshaft reluctor ring.
These systems degrade with age and mileage, resulting in inconsistent spark delivery or misfires. Ignition problems can also cause a rough idle, loss in power and acceleration, reduced fuel economy and even stalling.
Upgrading the system with high-quality components will deliver a more powerful spark, resulting in increased engine efficiency and performance.
The cost of repairing an ignition system varies *wildly* depending on the problem and your vehicle. A simple spark plug replacement might run you $100-$300, while replacing an ignition coil could be $150-$400 per coil (and some engines have multiple).
More complex issues like a faulty distributor or electronic control module can easily exceed $500-$800 in parts and labor. Diagnosing the problem usually involves an hourly rate of around $100-$150 at most shops.
Don’t automatically assume the worst! A good mechanic will provide a detailed estimate *before* starting any work, outlining all costs involved. If you're comfortable with DIY repairs, many ignition components are relatively easy to replace yourself – saving you significant labor costs.
Several components can fail in an ignition system. Spark plugs are often the first to go, wearing down over time and reducing spark intensity. Ignition coils can also fail, leading to weak or no spark at all.
The distributor (in older cars) is prone to wear and tear on its cap, rotor, and internal components. Sensors like the crankshaft position sensor can malfunction, sending incorrect timing signals to the engine control unit. Worn wires and corroded connections are also common culprits.
Diagnosing ignition problems often involves checking for spark at each cylinder, testing coil resistance, and inspecting wiring harnesses. A scan tool can help identify issues with sensors or electronic modules.
The biggest difference lies in how they control the spark. Older cars used a breaker-point system, relying on physical contact points that open and close to interrupt the electrical circuit. These require regular adjustment and wear out over time.
Electronic ignition replaces those mechanical points with an electronic module. This means no more maintenance, more consistent spark, and improved reliability. It also allows for finer control of timing. Think of it like upgrading from a manual typewriter to a computer – both get the job done, but one is far more precise and efficient.
Modern engines almost exclusively use distributorless (or direct) ignition systems which are even more advanced, eliminating the distributor entirely for better performance and fewer moving parts.
Several symptoms can indicate a problem with your ignition system. The most common is a difficult start – the engine cranks but doesn’t fire up easily. You might also experience misfires, where the engine runs rough or feels like it's losing power intermittently.
Other signs include a check engine light (often with codes related to misfires), reduced fuel economy, and noticeable hesitation during acceleration. In more severe cases, the engine may stall completely while driving. A consistent clicking sound when trying to start the car can also point to ignition issues.
It’s best to have it diagnosed by a mechanic if you suspect an issue; ignoring it can lead to further damage. Simple tests like checking spark plug condition are easy DIY, but pinpointing the exact cause often requires specialized tools.
