Testing The Ignition System (1998-2003 3.9L Dodge Dakota)

This tutorial will explain how to test the 1998-2003 3.9L V6 Dodge Dakota's ignition system to see if it's behind a misfire problem or a no-start problem.

All of the tests are explained in a step-by-step manner. You'll be able to easily diagnose the following components: spark plug wires, distributor cap and rotor, and the ignition coil.

You can find this tutorial in Spanish here: Cómo Probar El Sistema De Encendido (1998-2003 3.9L V6 Dodge Dakota) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles since they use the exact same ignition system components covered by this tutorial:

• 3.9L Dodge Dakota: 1998, 1999, 2000, 2001, 2002, 2003.
• 3.9L Dodge Durango: 1998, 1999.

WIRING DIAGRAM: The following ignition system wiring diagrams will further help your ignition system diagnostic:

• Ignition System Circuit Diagram (1997-1999 3.9L Dodge Dakota).
• Ignition System Wiring Diagram (2000 3.9L Dodge Dakota).
• Ignition System Wiring Diagram (2001-2003 3.9L Dodge Dakota).

Ignition System Test Basics

The components that make up the ignition system on the 1998-2003 3.9L Dodge Dakota are:

• The distributor.
• The distributor cap and rotor.
• The ignition coil.
• The spark plug wires (high tension wires).
• The crankshaft position sensor.
• The camshaft position sensor.

When you turn the key to crank and start the engine, this is what happens:

1. The camshaft position sensor starts to generate and feed a position signal to your Dodge Dakota's PCM (Powertrain Control Module = Fuel Injection Computer).
2. The crankshaft position sensor starts to generate and feed a position signal to your Dodge Dakota's PCM.
3. Once the fuel injection computer receives the camshaft and crankshaft position sensor signals, it sends the ignition coil an activation signal.
4. Once the ignition coil is activated by the PCM, it starts to spark.
5. The ignition coil's spark is transmitted to the center of the distributor's cap by a high tension wire.
6. The distributor rotor then distributes the spark to the distributor cap towers.
7. From the distributor cap towers the spark is transmitted to the spark plugs via high tension wires.

With the help of this tutorial you'll be able to check the ignition coil's high tension wire, the spark plug wires, the distributor cap, and the ignition coil.

What Tools Do I Need To Test The Ignition System?

The most important tool that you're gonna' need is a dedicate spark tester for all of the spark tests. Here are my recommendations:

• An HEI spark tester
  • You can see an example of this tool here: OTC 6589 Electronic Ignition Spark Tester.
• An LED light.
  • You can see an example of this LED light here: The LED Light Test Tool And How To Make One.
• Battery jump start cables.
• A multimeter.
  • If you don't have a multimeter or would like to upgrade yours, see my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
• A helper.

TEST 1: Testing The Spark Plug Wires For Spark

The first test we're gonna' do is to check for spark at all six spark plug wires.

We need to find out if any of the spark plug wires are not transmitting spark.

For the accuracy of your ignition system diagnostic, you should test all six spark plug wires.

To get the most accurate test result (from your spark tests), you should use a dedicated spark tester.

These are the test steps:

1. 1

   Disconnect the spark plug wire from its spark plug.

2. 2

   Attach the HEI spark tester to the spark plug wire (see the photo above).

3. 3

   Connect the HEI spark tester to the battery negative (-) terminal with a jump start cable.

4. 4

   Have your assistant crank the engine while you observe the spark tester. If you're testing a misfire condition, the engine will start so be careful.

5. 5

   You're going to see only one of two results: the spark tester will spark or it won't spark.

6. 6

   Repeat the spark test on the remaining spark plug wires.

Let's take a look at your test results:

CASE 1: All spark plug wires have spark. This is the correct and expected test result.

You can conclude that the following components are OK:

• Spark plug wires.
• Distributor cap and rotor.
• Ignition coil.
• Crankshaft position sensor.

If your Dodge Dakota's 3.9L V6 engine is misfiring, take a look at the suggestions found here: Other Causes Of A Misfire.

CASE 2: All spark plug wires have NO spark. This lack of spark will cause your 3.9L Dodge Dakota's engine to not start.

The next step is to check that the ignition coil's high tension wire is delivering spark to the distributor cap. For this test go to: TEST 3: Testing The Ignition Coil's High Tension Wire For Spark.

CASE 3: Some but not all of the spark plug wires sparked. The spark plug wires that are not sparking will cause a misfire problem.

The next step is check for spark directly on the distributor cap towers that feed spark to the wires that did not fire off spark. For this test go to: TEST 2: Testing For Spark At The Distributor Cap.