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Ignition system - Tips on check-up, common defects and replacement
The ignition system is used to ignite the fuel-air mixture in the combustion chamber. It triggers the explosion which pushes the piston in the desired direction and unfolds in this way the whole power in the engine.
From spark plug to the alternator
The ignition system is based on the sudden discharge of a high voltage electricity. The quality of the ignition relies on the power of the spark, its duration and its size. The stronger a spark is, the more precise the combustion of the air-fuel mixture is.
The path of the voltage
The alternator produces the electricity for the ignition system. Then, the generators fixed on the engine provide - depending on the vehicle - a voltage of 3-24 volts. Small motorcycles often still have 3 volt circuits, while heavy duty trucks have up to 18-24 Volt wiring systems. Cars typically have a 12-volt system, but due to the always increasing number of electrical consumers in newer cars, the default will soon be 18 volts. An effective ignition requires however far more than 24 volts. That’s why the voltage must be stepped up. This is the task of the ignition coil. The ignition coil is a simple transformer which is firmly fixed on to the body of the car. When the ignition voltage leaves the transformer it has tens of thousands of volts. Due to the low current, this voltage is not life threatening. Nevertheless, it is not pleasant to touch an operating ignition cable. The stepped-up voltage passes through the breaker, which in modern vehicles is controlled completely electronically. Older vehicles usually have a mechanical switch, which is no longer used today because of its susceptibility to failure. From the breaker the voltage goes into the distributor. This always directs the ignition voltage to the correct combustion chamber. To date, the system of the distributor rotor arm and the ignition wire connected to the cap has proven to be very effective. The voltage goes from the distributor into the ignition cable, which consist solely of a thick cable and the appropriate connectors. Finally, the ignition voltage arrives at the spark plug, which is firmly fixed on the motor.
How to detect damage to the ignition system
At a car with a faulty ignition system, two things can happen: Either the car drives with turbulences or it doesn’t drive at all. If the car has difficulties at starting or if the engine goes out while driving, the cause is most likely a faulty ignition system. In the first place you should check whether all cables are still in place and plugged in. For the drive to continue is often enough to plug an unplugged ignition cable back again. From spark plug to distributor, all components are low-priced consumables. The maintenance manual of the vehicle has fixed replacement intervals for the spark plugs. It is useful to check the distributor at each spark plug replacement. To check it, you have to unplug it and look inside of it. If strong burn marks have formed on the the four to eight contacts (always exactly as many as the number of cylinders), you should replace them. As gap measure you can freely scratch the contacts with a screwdriver. However, once you have the opportunity to buy a new one, you should replace the cap. Should the ignition cable lose its insulation, the voltage will no longer reach the spark plug. You can detect this, for example, by running the vehicle in the dark with the hood open. The defective ignition cable will produce a flash. Do NEVER do this test in a closed space (such as a garage) !!! Exhaust gases are VERY poisonous and can lead to death within a short time! Better wait for the night and run this test outside.
It is recommended to replace the ignition cable always entirely. Even if just one cable is damaged by martens, for example, if you buy a new set of ignition cables you bring your ignition system back in a defined state, on which you can rely.
At the replacement of the spark plugs, it is very important to choose the exact models approved for your car model by the manufacturer. The spark plug has numerous specific values such as: length of the thread, heat value and permissible voltage. Each of these values must match exactly for your vehicle model, otherwise you risk a fatal engine damage.
In our online shop you will find all the components of the ignition system in a car. We sell only approved, high-quality products, which support a long engine life.