How To Test The Ignition Coil (1989-1991 3.9L V6 Dodge Ram Pickup)

TEST 6: Testing The Ignition Coil's Activation Signal

We've covered a lot of Ground so far! At this point, here's what your tests have confirmed:

• TEST 1: None of the six spark plug wires are producing spark.
• TEST 3: No spark coming from the ignition coil's high tension wire.
• TEST 4: Still no spark directly from the ignition coil's tower.
• TEST 5: The ignition coil is getting a solid 10 to 12 Volts.

Now it's time for the last test in this tutorial —we're gonna see if the ignition coil is getting its activation signal from your Dodge Ram's fuel injection computer (PCM).

This trigger signal comes through the wire connected to the ignition coil terminal marked with a (-) symbol.

To check for that signal while the engine is cranking, we'll use a regular 12-Volt automotive test light.

If you don't have one, this is the one I use and recommend: Lisle 28400 Heavy Duty 12 Volt Test Light (at: amazon.com).

Let's begin this final test:

1. 1

   Clip the alligator end of your 12V test light to the battery's positive (+) post.

2. 2

   Touch the metal probe to the ignition coil terminal marked with a (-) symbol.
   
   NOTE: Leave the wire connected to the terminal.

3. 3

   Have your helper crank the engine while you keep the test light probe on that negative terminal.

4. 4

   The test light should blink ON and OFF while the engine's cranking.
   
   NOTE: Don't pay attention to what the light does before or after cranking —only watch what it does during engine cranking.

Now let's break down what those results mean:

CASE 1: The test light blinked ON and OFF. That's the correct result and the one we need to see.

This means the ignition coil is getting its activation signal to fire spark —and if all of the following are also true:

• No spark from the plug wires (TEST 1).
• No spark from the high tension wire (TEST 3).
• No spark at the ignition coil's tower (TEST 4).
• The coil is getting 10 to 12 Volts (TEST 5).
• And now, it's getting its activation signal (TEST 6).

Then there's only one conclusion —the ignition coil is bad. It has power, it's getting triggered, and it's still not sparking. Swap it out to fix your V6 Dodge Ram pickup's no-start problem.

CASE 2: The test light didn't flash ON and OFF. That tells you the ignition coil isn't receiving its activation signal. Without that signal, it can't fire spark —plain and simple.

Double-check your test setup and give it another shot. Still no ON/OFF flash? The most likely issue is a bad distributor pickup coil.

This tutorial will help you test the distributor pickup coil on your 1989–1991 3.9L V6 Dodge Ram:

• How To Test The Distributor Pickup Coil (1989-1991 3.9L V6 Dodge Ram Pickup).

Other Causes Of A Misfire

Quite a few things, when they malfunction, can cause a misfire (rough idle). So if you went through this whole tutorial and everything checked out, here are a few other things you'll want to take a look at:

1. Spark plug wires: Give the wires a close inspection.
   • Make sure none of the wires are missing their metal terminal —that's the little metal piece that actually connects to the spark plug. It's not unheard of for someone to yank a wire off and leave the terminal stuck on the plug... then pretend nothing happened (yep, true story —LOL).
   • Check that no wires are burned or melted by the exhaust manifold —another common issue. If a wire has a burn-through spot, the spark is jumping out that spot instead of reaching the spark plug.
2. Spark plugs: Pull them out and take a good look.
   • Look for cracked or broken porcelain —especially if you recently did a tune-up and one might've been dropped.
   • If you pressure washed the engine lately, that could be the culprit too. Power washing the engine can cause quite a bit of head-aches until everything dries out.
3. Carbon tracks: Check the plugs for carbon tracking.
   • These little black lines can form on the porcelain or inside the spark plug boots and cause the spark to be channeled to the side of the engine —leading to a misfire. You can see what they look like in the photo above.
4. Engine compression: Worn valves or piston rings can cause low compression —and that'll make a cylinder misfire too.
   • Compression problems are one of the most overlooked causes of misfires.
   • Here's a full walkthrough: How To Test The Engine Compression (1989–2001 3.9L V6 Dodge Ram Pickup).

You might also find these real-world case studies helpful —they walk through how I've tracked down and fixed misfires in different scenarios:

• Diagnosing A Toyota Corolla Misfire Case Study.
• Troubleshooting A Hard To Diagnose Misfire Case Study (GM 3.1L, 3.4L).
• Carbon Tracks Are A Common Cause Of Ignition Misfires (at: easyautodiagnostics.com).

Where To Buy The Ignition Coil And Save

The following links will help you to comparison shop and hopefully save you a few bucks on its purchase:

NOTE: The ignition coil fits the following vehicles: 1989-1991 3.9L V6 Dodge Ram pickup.

Where To Buy The Distributor Cap, Distributor Rotor, Spark Plug Wires And Save

The following links will help you to comparison shop and hopefully save you a few bucks:

NOTE: The distributor cap, the distributor rotor, and the spark plug wires fit the following vehicles: 1989-1991 3.9L V6 Dodge Ram pickup.

More 3.9L V6 Dodge Ram Pickup Tutorials

You can find a complete list of 3.9L V6 Dodge Ram Pickup tutorials in this index:

• 3.9L V6 Dodge Ram Pickup Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• Throttle Body Temp Sensor Tests (1989-1991 3.9L V6 Dodge Ram Pickup).
• How To Test The TPS (1989-1990 3.9L V6 Dodge Ram Pickup).
• How To Test The Fuel Pump (1989-1991 3.9L V6 Dodge Ram Pickup).
• How To Test For A Blown Head Gasket (1989-2001 3.9L V6 Dodge Ram Pickup).