Ignition Coil – Coil Types – Failure Symptom Warning Signs

Ignition Coil
Ignition Coil

The ignition coil’s job is to produce a high voltage from a low voltage.

The high voltage from your ignition coil is needed to ignite the fuel and start the engine.

So, Inside the ignition coil are two sets of windings.

The primary coil windings contain hundreds of turns of heavy wire.

While the secondary side contains thousands of turns of fine wire.

In older vehicles, a single coil would service all the spark plugs and use a distributor.

In modern systems, the distributor is omitted and the ignition coil is electronically controlled.

And, With all this new technology come new issue to solve.

Failure Symptoms

The severity of the symptoms vary according to which of the ignition coils are failing.
  • Backfiring
  • Fuel Economy
  • Vehicle Stalling
  • Engine Jerking, Rough idling, Poor Power
  • Engine does not start
  • Vehicle misfires
  • Poor acceleration or loss of power
  • Engine control unit switches to limp-home mode
  • Engine fault codes

If the coil malfunction is causing misfiring, this will allow raw fuel to enter and permanently damage the catalytic converter.

Catalytic Converter
Catalytic Converter

Taking steps to check for oil leaks, moisture, and spark plug issues will prevent serious engine damage.

The most likely cause is a oil leak from the valve cover gasket. On many COP-style engines the spark plug and ignition coil are mounted inside a spark plug tube. This tube seals in place around part of the valve cover.

Overtime the seal between the valve cover and that spark plug tube can fail. Consequently, Causing oil to leak in and fill up around the spark plug and ignition coil. This in turn can lead to spark plug and ignition coil failure.

Ignition Coil Types

There are basically four main types of ignition coils:


Conventional Ignition Coil
Conventional Ignition Coil

So, With the conventional breaker point-type ignition system the primary circuit receives power from the battery through a resistor. Current flows through the winding’s of the primary coil, creating a magnetic field. When the points are opened the current’s electrical circuit is broken, collapsing the magnetic field.

The force from the collapse crosses the winding’s of the secondary coil and creates an electrical current within them.

The current flows into the distributor cap and eventually into the spark plugs, all in a split second. But, These early, fully mechanical distributor systems had their shortcomings. The ignition points would break down and change spark timing, messing up engine efficiency. As a result, Requiring replacement as often as every 12,000 miles.


Electronic Ignition Coil
Electronic Ignition Coil

So, This type of ignition is very similar to the conventional system. But instead of a distributor cam and points, the electronic system uses a pickup coil to signal the control module.

Doing so increased reliability, but the solid-state switches still took their marching orders from the distributor shaft.

Distributor shafts would tend to develop a certain amount of “lash” or slop after 120,000 or so miles. Since gear wear would always be an impediment to proper spark timing, mechanical ignition systems had to evolve.


Distributorless Ignition Coil
Distributorless Ignition Coil

So, In a distributorless ignition system, its design allowed more energy to be available from multiple coils. Also, There are three or more mounted together in a coil pack.

This system uses a magnetic triggering device to determine engine speed and crankshaft position. This system determines spark timing based on two shaft position sensors and a computer.

The Crankshaft Position Sensor (CKP) and the Camshaft Position Sensor (CMP). These sensors continually monitor both shafts’ positions and feed that information into a computer.


Coil-on-Plug Ignition
Coil-on-Plug Ignition

So, The coil-on-plug (COP) ignition system incorporates all the electronic controls found in a DIS ignition system. But instead of two cylinders sharing a single coil, each COP coil services just one cylinder.

As a result, some COP car ignition systems generate as much as 50,000 volts and much hotter, stronger sparks.

Since the coil mounts directly on top of the spark plug, spark plug wires were eliminated.


So, Heat and vibration can damage the coil’s windings and insulation. As a result, Causing shorts or open circuts in the primary or secondary windings.

Finally, The Top Failure Reasons:

  • Bad spark plugs. …
  • Bad plug wires. …
  • Voltage overload. …

Consequently, New spark plugs will help ignition coils last longer.

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