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Ignition System Faults 1

Ignites the petrol engine in such a way, that, if possible, knocking doesen't take place.

The electric ignition system is, at the moment, the last remaining sure sign that it is a petrol driven engine. It has the job of igniting the fuel air-mixture under all operating conditions in such a way that the pressure increase occurs shortly after TDC. Although the ignition should take place as early as possible but, under no circumstances, too early, otherwise spontaneous combustion can take place, causing knocking. Nowadays, the ignition timing is mostly electronically regulated for any working condition by the stored values (characteristics map), or through supervision, e.g., by the knocking sensor.

The energy comes from the battery or the generator.

The production of an electric arc in the spark-plug is called induced ignition. This is made possible by converting 12V-DC into, generally more than 10.000V of high-tension. The energy (see figure) comes either from the battery (starting), the generator (engine running) or from a permanent magnet. To achieve the high tension, a transformer (mostly in stand-by mode) is also necessary. In multi-cylinder engines, there is an exactly determined firing order, which depends, not only on the number of cylinders, but also on how they are arranged. Modern ignition coils are connected either, one for each individual cylinder or one for every two cylinders.

The ignition is fully intergrated into the engine management.

It's predecessors are the glow-pipe-, the buzzer and the magneto ignition, of which only the latter has survived. The electronic ignition helps in the decontamination of exhaust gases and in the avoidance of CO2 emission. It has become an intergrative component of the engine management. From the outside, only components like the ignition and the spark-plugs can be recognised. In the meantime, even this is being used as a sensor for the overall system and thus, replaces, e.g., the knocking sensor.

Induction: an electric conductor intersects a magnetic field.

To generate an electric arc, a much higher tension than the battery can supply is necessary. This is achieved through induction. Induction occurs at the ends of a conductor then, when one moves it through a magnetically or electrically built up field. The word itself comes from the Latin verb 'inducere', and means roughly, 'to lead in'. Apart from the ignition, one can observe induction in any relay, the inductive sensor and also in an electric motor or generator.

Either the magnetic field or the electric conductor moves.

Rolled up, mutually isolated wire is called a coil, and it doesn't matter at all, whether the coil-, or the permanent magnet does the moving. One can also move a coil with a current-flow past one where no current is flowing, tension is always measurable on the latter, whose plus-/minus-alignment depends on the direction of the movement through the force-field.

Important error indication through the ignition firing line

The oscilloscope display of the secondary circuit is almost more important today than it was before, it takes no time at all to connect up and be ready for analysing. In this case e.g., a divergent high tension is immediately obvious. It is also called the ignition firing line. If, e.g., it is lower than that of the other cylinders, then either the spark plug gap is too big or the mixture is too lean. This of course, also applies if the spark plug gap is too small. It is also important to ensure that the individual cylinders are shown in the firing order. 03/12

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