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

TEST 3: Testing The Ignition Coil's High Tension Wire For Spark

If all 6 spark plug wires DID NOT spark during TEST 1, there's good chance the high tension wire that connects and delivers spark from the ignition coil to the distributor cap is bad (a very common problem).

In this test section, we're gonna check whether the ignition coil's high tension wire is actually able to deliver spark when the engine cranks.

Let's get going:

1. 1

   Unplug the high tension wire from the center of the distributor cap.
   
   NOTE: Leave the other end of the wire connected to the ignition coil.

2. 2

   Connect your spark tester to the loose end of that wire —the one you just pulled off the cap (use the photo above as a guide).
   
   NOTE: Make sure the ignition coil end of the high tension wire stays plugged into the ignition coil.

3. 3

   Ground the spark tester to the battery's negative (-) terminal with a jumper cable.

4. 4

   Have your helper crank the engine while you keep an eye on the spark tester.

5. 5

   You should see spark at the tester the entire time the engine is cranking.

Here's what your results tell you:

CASE 1: You get spark. That's what you want to see.

This means the high tension wire and the ignition coil are working fine, and the issue is inside the distributor —either the cap or the rotor is at fault. But that's only true if both of these are also confirmed:

• None of the spark plug wires sparked in TEST 1.
• You just confirmed that the coil is sending spark through the high tension wire.

To get your V6 Dodge Ram pickup back up and running, replace the distributor cap and rotor. If the spark plugs and spark plug wires are old too, go ahead and replace those while you're at it.

CASE 2: No spark at all. That means the distributor isn't getting any spark.

Your next step is to test the ignition coil directly at the tower. Head here: TEST 4: Testing The Ignition Coil For Spark.

TEST 4: Testing The Ignition Coil For Spark

If you've made it to this point, then TEST 1 and TEST 3 confirmed two key things:

• TEST 1: No spark from all 6 spark plug wires.
• TEST 3: No spark from the ignition coil's high tension wire.

To further troubleshoot the problem, we're now gonna check for spark directly at the ignition coil's tower —just like I'm doing in the photo above.

This is what we can expect:

Spark: This confirms the ignition coil itself is working —the problem is the high tension wire. It's not carrying the spark to the distributor cap (a very common failure).

No Spark: We'll move on to the next step (TEST 5) and check that the ignition coil is getting power.

These are the test steps:

1. 1

   Unplug the high tension wire from the ignition coil.

2. 2

   Connect your spark tester directly to the ignition coil's tower (just like in the photo above).

3. 3

   Ground the tester by clipping it to the battery's negative (-) terminal using a jumper cable.

4. 4

   Have your helper crank the engine while you watch the spark tester.

5. 5

   The spark tester should spark while the engine's cranking.

Now let's break down what your spark test results mean:

CASE 1: You saw a steady spark. That's exactly what you want to see.

This proves the ignition coil is working fine. And if you've already confirmed these:

• No spark from any plug wire (TEST 1).
• No spark from the ignition coil's high tension wire (TEST 3).
• But now, spark shows up right at the coil tower (this test).

This confirms the ignition coil's high tension wire is bad. Replace that wire to get your engine back in action.

NOTE: Go ahead and swap out the whole spark plug wire set, not just that one wire.

CASE 2: Still no spark. That tells us the ignition coil itself isn't firing spark at all.

Next up, we need to check that the coil is getting power. To do that, head to: TEST 5: Making Sure The Ignition Coil Is Getting 12 Volts.

TEST 5: Making Sure The Ignition Coil Is Getting 12 Volts

The ignition coil gets 10 to 12 Volts from the Auto Shutdown (ASD) Relay, and in this test section, we'll check this.

As you're already aware, two wires connect to the ignition coil. The wire responsible for delivering this voltage is either:

• A gray (GRY) wire.
• A dark green with black stripe (DK GRN/BLK) wire.

This power supply wire connects to the ignition coil terminal marked with a (+) sign. In the photo above, I've labeled the wire with the number 1.

I need to point out that we have to crank the engine to check for voltage at that terminal. If the engine isn't cranking, you're not gonna see any voltage.

CAUTION: You'll need to crank the engine to run this test, so stay alert and take all necessary safety precautions.

Alright, here's how to run the check:

1. 1

   Switch your multimeter to DC Volts mode.

2. 2

   Touch the red probe to the coil terminal marked (+).
   
   NOTE: You don't need to unplug the wire from the coil to test it —just probe it with the wire still connected.

3. 3

   Connect the black probe to the battery's negative (-) post.

4. 4

   Have your helper crank the engine while you keep your eye on the multimeter.

5. 5

   You should see 10 to 12 Volts on the display as the engine cranks.

Here's what your results mean:

CASE 1: You see 10 to 12 Volts at the (+) terminal. That's the result you want —the ignition coil is getting power.

Since you're chasing down a no-spark no-start issue, your next step is to check if the coil is getting its trigger (activation) signal. Head over to: TEST 6: Testing The Ignition Coil's Activation Signal.

CASE 2: No voltage at the (+) terminal. That tells us the ignition coil isn't receiving power —which means it can't generate spark.

This usually means there's an issue with the wiring —most likely a break in the wire running between the ASD relay and the coil's (+) terminal.

This could also be due to a bad distributor pickup coil. This tutorial will help you test it:

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