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Ignition System Service - Houston's Premier Auto Repair Facility

The ignition system creates the spark that ignites fuel and air in a gas engine. The ignition coil increases the 12 volts supplied by the battery to around 20,000 volts. Although older vehicles used a single ignition coil and a mechanical distributor to send the high voltage to each spark plug, most vehicles now have a smaller ignition coil for each cylinder of the engine.

The engine computer determines when the spark should happen by the signal it receives from the crankshaft position sensor. The timing is further fine-tuned according to readings from other sensors such as the knock sensor, which listens for the noise created when the spark happens too early, the throttle position sensor, and the mass air flow or manifold pressure sensors. A variety of sensors are used to ensure proper timing of the engine spark.

When the engine computer activates the coil, the high voltage jumps the gap between the electrode and group strap on the spark plug, igniting the compressed fuel and air in the cylinder to create an explosion that pushes the piston downwards.

Failed or worn ignition system components cause misfires -- where the fuel is not burned correctly in the cylinder. This causes rough running, loss of power, and increased fuel consumption.

The ignition coil and spark plug are the primary elements of the ignition system, providing the voltage to create a spark. 

What parts make up the ignition system?

  • Spark plug: An electrical device that is connected to a high voltage source. The high voltage travels down an electrode inside the spark plug and arcs across an air gap, thereby creating the spark that starts the combustion process in the combustion chamber.

  • Spark plug wire set: They transfer the spark from the distributor or ignition coil to the spark plugs that ignite the air-fuel mixture. 
  • Ignition coil: Transfers the low 12-volt battery ignition primary current into the high voltage secondary current that fires the spark in the plugs. The current through the primary coil windings builds up an electromagnetic field around the ferrous core of the coil. When the current is suddenly shut off, the electromagnetic field collapses and generates the high voltage in the secondary windings. 

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