Coil replacement

What are coils? I did replace my sparkplugs, and they said one coil was gone, and I replaced all three in the back. What do they do

Coils are electrical transformers, basically, that take the 12 volt battery current and transform it into high-voltage current to make the spark. Without the coil, the 12 volt current would not be strong enough to generate a spark. No coil = no spark.

They enable the engine to send high voltage pulses to the sparkplugs using only 12VDC as a source. They’re what’s called “inductive devices”. A 12VDC wire is wound around an iron core and current is sent through it. The current creates a magnetic field. When it’s time for the spark plug to fire, the 12VDC circuit is disconnected (disenabled) and when the current stops flowing the magnetic field collapses into the iron core, sending a high voltage spike through the core. That spike is sent directly to the center electrode of the spark plug, it creates a large difference in charge between the center electrode and the ground electrode, and the charge discharges across the sparkplug gap to ground, the arc igniting the fuel in the cylinder.

In days of old cars had one “coil” and a “distributor”. The coil “primary” circuit was turned on and off by mechanically operated contacts called “points” and the “distributor” distributed the spark to the correct spark plug. The “points” and the distributor’s “rotor” were turned by the cam shaft, keeping the spark in time with the cylinders.

In modern cars, each individual spark plug has its own coil. That eliminates the losses inherant in spark plug wires.

Hey, thanks so much for this enlightment! Guess the coils are very important…glad I had them replaced.