How To Test The Coil Pack (Ford 3.0L, 3.8L, 4.0L, 4.2L)

In this article I'll shed some light on how to test and diagnose a Ford (and Mercury) V-6 ignition coil pack. You'll learn how to test it on the car and without using a scan tool.

The tests are fast and easy and I'll take you thru' the whole process step by step with photos, by explaining the do's and don'ts, and by teaching you some basic working theory all in plain English. Also and just as important, these tests will help you save money by correctly diagnosing the Ford coil pack as bad or eliminating it as the source of the problem (misfire or no-start).

You can find this tutorial in Spanish here: Cómo Probar la Bobina de Encendido (Ford 3.0L, 3.8L, 4.0L, 4.2L) (at:

There are two other ignition system test articles that might be of interest: If you need to test the 1.9L/2.0L 4 cylinder Ford coil packs, click here: How To Test FORD 4 Cylinder Coil Packs. Or if you need to test the 4.6L/5.4L V8 Coil-on-Plug Ford ignition coils, click here: How To Test Ford Coil-On-Plug (COP) Ignition Coils.

Symptoms Of A Bad Ford Ignition Coil Pack

The following are the most common symptoms of a bad Ford ignition coil pack but not limited to:

  1. The check engine light is on:
    1. Due to misfire codes (P0300, P0301, P0302, P0303, P0304, P0305, P0306).
    2. Or due to other ignition system malfunction codes.
  2. Rough idle.
  3. Bad gas mileage.
  4. Excessive tail-pipe emissions (pollution).
  5. A "rotten egg" smell coming from the tailpipe.
    1. This smell is caused by unburned gasoline from the misfiring cylinder overloading the catalytic converter's oxidation process.
  6. Engine misfires under load. In other words; as you accelerate the car (or truck) and it starts to move, the engine starts to miss.

The Two Types Of The Ford V-6 Ignition Coil Pack

How To Test The Coil Pack (Ford 3.0L, 3.8L, 4.0L, 4.2L)

Ford uses two types of coil packs for the Ford and Mercury models that have a V-6.

The differences between both types can be summed up as: Early design (Type 1) and late design coil pack (Type 2 -the late design coil pack is also known as the Series 5 coil pack in Ford technical speak). Both types are tested in the exact same way because their circuits and the cylinders they feed (with spark) are identical!

If you're wondering what these two look like, the photo above is of the early design (type 1) and the illustration below is of the late design (type 2) ignition coil pack.

Also, even tho' many Ford and Mercury models use the exact same coil pack, the type of connector and the color of the wires used vary a lot! Once, again, these differences don't make a lick of difference. The circuits and their descriptions and more importantly their tests are the same regardless of the color of the wires, or the shape of the connector or the year or the angle, etc.

How To Test The Coil Pack (Ford 3.0L, 3.8L, 4.0L, 4.2L)

What Tools Do I Need To Test The Ford V-6 Ignition Coil Pack?

You'll test and diagnose the Ford coil pack on the car or truck with some very basic tools. You'll need:

  1. A test light.
  2. A multimeter.
    1. You can use a digital multimeter or an analog multimeter.
    2. If you need to buy one or are looking to upgrade, check out my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
  3. An HEI spark tester.
    1. This inexpensive spark tester is a MUST have tool to be able to correctly diagnose the ignition coil pack on your Ford (or Mercury or Mazda) vehicle with the info/tests in this article (don't have an HEI spark tester? Need to buy one? You can buy it here: OTC 6589 Electronic Ignition Spark Tester).
  4. A tool that can pierce thru' the wires insulation. Such as a wire-piercing probe.
    1. This is one of the handiest tools ever invented. To see what this tool looks like, go here: Wire Piercing Probe.
  5. You'll need a helper to help you crank the engine while you perform the tests.
  6. A car (or truck) shop manual (no, not the Owner's Manual) for the specific Ford or Mercury model that you're working on. This manual is not a must for these tests, but may come in handy if you need some specific info this article doesn't provide.

You DO NOT need a scan tool (automotive diagnostic scanner) to test the Ford coil pack, in case you're wondering why there's no mention of a scan tool in the list above. Why? Well, because a scan tool can not do a live performance test on the coil pack like the one this article is gonna' teach you to do.

Don't get me wrong, a scanner helps (or how else are you gonna' retrieve the codes in the fuel injection computer's memory?) but all of the tests in this article are performed without a scan tool.

Safety Precautions and Guidelines

Since you'll be working around a cranking engine this section can be summed up with the following: use common sense and take all necessary safety precautions.