How To Test The Ignition Coil (1989-1991 5.2L, 5.9L V8 Dodge Ram Pickup)

By: Abraham Torres-Arredondo
Created: 24 April 2025
Updated: 26 April 2025
Articl Id: 1690

Page 3 of 3

TEST 6: Testing The Ignition Coil's Activation Signal

Testing The Ignition Coil's Activation Signal. How To Test The Ignition Coil (1989, 1990, 1991 5.2L, 5.9L V8 Dodge Ram Pickup)

You've done quite a bit of testing so far! At this point, you've confirmed the following:

TEST 1: No spark from any of the eight spark plug wires.
TEST 3: The ignition coil's high tension wire isn't sparking.
TEST 4: No spark coming from the ignition coil's tower.
TEST 5: The ignition coil is getting 10 to 12 Volts.

For the final test in this tutorial, we're gonna check if the ignition coil is receiving its activation signal from your Dodge Ram pickup's fuel injection computer.

This signal is delivered by the wire that connects to the terminal on the ignition coil labeled with a (-) symbol.

To check for that signal while cranking the engine, we'll use a standard 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 get to it:

1
Clip the alligator end of your 12 Volt test light to the battery's positive (+) terminal.
2
Touch the metal probe of the test light to the ignition coil terminal marked with a (-) symbol.

NOTE: Leave the wire connected to that terminal.
3
Have your assistant crank the engine while you keep the test light's probe on that (-) terminal.
4
The 12 Volt test light should blink ON and OFF the entire time the engine is cranking.

NOTE: Ignore what the light does before or after cranking. You only care about what happens while the engine's being cranked.

Here's how to read your results:

CASE 1: The test light blinked ON and OFF. That's exactly what you want to see.

With this result, you can say for sure the ignition coil is bad —but only if all of the following are also true:

No spark from any spark plug wire (TEST 1).
No spark from the coil's high tension wire (TEST 3).
No spark at the coil's tower (TEST 4).
The ignition coil is receiving 10 to 12 Volts (TEST 5).
The coil is getting its activation signal (TEST 6 —this test).

Here's the logic: If the ignition coil has power and it's getting its signal, it should be sparking. If it's not, the coil is faulty and needs to be replaced.

To fix your V8 Dodge Ram pickup's no-start issue, replace the ignition coil.

CASE 2: The test light did NOT flash ON and OFF. That means the ignition coil isn't getting its activation signal, and without that, it won't fire any spark.

Double-check all your connections and try the test again. If the test light still doesn't flash, the most likely cause is a failed distributor pickup coil.

Use this step-by-step tutorial to test the pickup coil on your 1989–1991 5.2L or 5.9L V8 Dodge Ram pickup:

How To Test The Distributor Pickup Coil (1989–1991 5.2L, 5.9L V8 Dodge Ram Pickup).

Other Causes Of A Misfire

A misfire (or a rough idle) doesn't always mean there's something wrong with the ignition system. So if you followed this tutorial and everything checked out fine, here are a few other things worth looking into:

Spark plug wires: Inspect the condition of the spark plug wires.
- Check that none of the spark plug wires are missing their metal terminal. This is the metal terminal that makes contact with the spark plug. It's not uncommon for someone to pull the wire off of the spark plug, for the terminal to stay stuck on the spark plug, and for them to hope no one notices (LOL).
- Check that none of the spark plug wires have been burned by the exhaust manifold, this is another common problem. If there's a burn thru spot on the wire, that wire is arching spark at that point and that spark isn't reaching the spark plug.
Spark plugs: Take a close look at the spark plugs.
- Check for cracked or broken porcelain insulators —especially if you recently did a tune-up and may have dropped one by accident.
- If you pressure washed the engine recently, that could also cause issues. Power washing isn't recommended on vehicles with electronic fuel injection.
Carbon tracks: Inspect for carbon tracks on the spark plugs.
- Carbon tracks can form on the porcelain insulator and inside the spark plug boot. These can short the spark and cause a misfire. The photo above shows you what they look like.
Engine compression: Worn valves or worn piston rings could be causing low cylinder compression, resulting in that cylinder misfiring.
- Compression testing is one of the most overlooked ways to track down a misfire.
- You'll find a step-by-step guide here: How To Test Engine Compression (1989–2003 5.2L, 5.9L V8 Dodge Ram Pickup).

These real life case-studies (of how I've diagnosed and resolved some cylinder misfire issues) might further help you:

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 ignition coil for the 1989-1991 5.2L/5.9L V8 Dodge Ram pickup is not an expensive part. The following links will help you to comparison shop and hopefully save you a few bucks on its purchase: