Checking the ignition system on your 1989–1991 Dodge Ram pickup with a 5.2L or 5.9L V8 isn't complicated. Also, you don't need a bunch of expensive diagnostic tools to do it!
In this tutorial, I'll walk you through how to figure out if the ignition system is causing either an engine no-start problem or a cylinder misfire issue.
You'll be testing the spark plug wires, distributor cap and rotor and the ignition coil. I'm also gonna give you the link to the tutorial that'll help you test the distributor pickup coil.
Contents of this tutorial:
- Ignition System Test Basics.
- What Tools Do I Need To Test The Ignition System?
- TEST 1: Testing The Spark Plug Wires For Spark.
- TEST 2: Testing For Spark At The Distributor Cap.
- TEST 3: Testing The Ignition Coil's High Tension Wire For Spark.
- TEST 4: Testing The Ignition Coil For Spark.
- TEST 5: Making Sure The Ignition Coil Is Getting 12 Volts.
- TEST 6: Testing The Ignition Coil's Activation Signal.
- Other Causes Of A Misfire.
- Where To Buy The Ignition Coil And Save.
- Where To Buy The Distributor Cap, Distributor Rotor, Spark Plug Wires And Save.
- More 5.2L, 5.9L V8 Dodge Ram Pickup Tutorials.
APPLIES TO: This tutorial applies to the following vehicles:
- Dodge Ram 150 Pickup 5.2L V8: 1989, 1990, 1991.
- Dodge Ram 250 Pickup 5.2L V8: 1989, 1990, 1991.
- Dodge Ram 150 Pickup 5.9L V8: 1989, 1990, 1991.
- Dodge Ram 250 Pickup 5.9L V8: 1989, 1990, 1991.
- Dodge Ram 350 Pickup 5.9L V8: 1989, 1990, 1991.
IGNITION SYSTEM WIRING DIAGRAM:
- Ignition System Circuit Wiring Diagram (1989 5.2L, 5.9L V8 Dodge Ram Pickup).
- Ignition System Circuit Wiring Diagram (1990-1991 5.2L, 5.9L V8 Dodge Ram Pickup).
DISTRIBUTOR PICKUP COIL TESTS:
Ignition System Test Basics
The ignition system on the 1989–1991 Dodge Ram 5.2L and 5.9L V8 uses a traditional, distributor-style setup. It's made up of these main parts:
- Ignition coil: Builds up and releases the high-voltage spark.
- Distributor: The mechanical component that routes the spark to the right cylinder.
- Distributor pickup coil: Acts as both the crankshaft and camshaft position sensor.
- Spark plug wires (also called high tension wires): Carry the spark from the distributor to each spark plug.
- Distributor cap and rotor: Work together to send the spark to each cylinder in the correct order.
Here's what goes down when you turn the key and crank the engine:
- CMP/CKP signal: The pickup coil inside the distributor kicks in, creating the cam and crank signal your pickup's fuel injection computer needs.
- Ignition coil activation: Once the computer gets that signal:
- Enables the ASD relay (this is the relay that powers the fuel injectors, fuel pump, and ignition coil).
- Activates the ignition coil to fire spark.
- Activates the fuel injectors to spray fuel.
- Spark sent to distributor: That spark travels through a high tension wire to the middle of the distributor cap.
- Distributor rotor: The rotor inside the cap spins and directs the spark to the right contact points under the distributor cap.
- Spark reaches spark plugs: From there, the spark goes through the spark plug wires and hits each spark plug.
This tutorial will help you check the ignition coil's high tension wire, the spark plug wires, the distributor cap/rotor, and the ignition coil itself.
What Tools Do I Need To Test The Ignition System?
You're gonna need a few tools to test the ignition system on your V8 Dodge Ram van. The good news? None of them will break the bank.
The number one tool you'll want on hand is a spark tester. Here's what I recommend:
- An HEI spark tester: This tool is a must if you want solid, reliable test results. It lets you confirm if there's spark the right way. You can check out and grab the one I use right here:
- OTC 6589 Electronic Ignition Spark Tester (at: amazon.com).
- A 12-volt test light: We'll use it to test for the ignition coil's activation signal. This is the one I have and use:
- Lisle 28400 Heavy Duty 12 Volt Test Light (at: amazon.com).
- Jumper cables: Yep, standard battery booster cables.
- A multimeter: If you're missing one or thinking about upgrading, this is the one I use and recommend:
- Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (at: amazon.com).
- Spark plug wire pliers: This must-have tool helps prevent damage to the wires while you're removing them from the spark plugs. If you don't have one, you can check it out and buy it here:
- OEMTOOLS 25542 Spark Plug Pliers. (at: amazon.com).
- And finally —a helper. Trust me, having someone to crank the engine while you test makes life easier.
TEST 1: Testing The Spark Plug Wires For Spark
Let's kick off our ignition system check by testing for spark —it's the first and most important step. This is how we'll figure out if the no-start or misfire problem is coming from the ignition system.
No matter if your Dodge Ram V8 won't start or it starts but runs rough, you've gotta check all 8 spark plug wires for spark.
Testing every wire matters. It's the only way to make sure your results are accurate and you're not chasing the wrong issue.
NOTE: You need to use a real spark tester. Any dedicated spark tester will work, but if you need to get one, I highly recommend the HEI spark tester. You can see what it looks like and buy one here: OTC 6589 Electronic Ignition Spark Tester (at: amazon.com).
CAUTION: You'll be cranking the engine while doing these tests, so stay sharp and take all the safety steps you need to.
Alright, let's dive in:
- 1
Unplug the spark plug wire from cylinder #1.
- 2
Hook up your HEI spark tester to that spark plug wire (refer to the photo above for guidance).
- 3
Use a jumper cable to Ground the spark tester by connecting it to the battery's negative (-) terminal.
- 4
Have your helper crank the engine while you watch the spark tester closely.
NOTE: If you're testing for a misfire, the engine might start up —be careful and stay alert. - 5
You'll get one of two outcomes: Either the spark tester sparks, or it doesn't.
- 6
Repeat the same spark test for the rest of the spark plug wires.
Now, let's break down what your test results mean:
CASE 1: All eight spark plug wires show spark. That's exactly what you want to see.
This means the ignition coil, the distributor cap and rotor, the pickup coil inside the distributor, and all the spark plug wires are working like they should.
If you're chasing down a misfire issue on your 1989–1991 Dodge Ram V8, check out these tips next: Other Causes Of A Misfire.
If you're troubleshooting and engine no-start problem, a lack of spark is not the cause of it.
CASE 2: None of the spark plug wires show spark. Your next move is to see if the ignition coil's high tension wire is actually sending spark to the distributor cap.
For this spark test, head here: TEST 3: Testing The Ignition Coil's High Tension Wire For Spark.
CASE 3: Only some spark plug wires are firing spark, and others aren't. This usually means one of two things: the spark plug wires are bad or the distributor cap is bad.
Don't worry, we can find out by testing for spark right at the distributor cap towers that connect to the dead wires. Go to: TEST 2: Testing For Spark At The Distributor Cap.
TEST 2: Testing For Spark At The Distributor Cap
If one or more spark plug wires didn't fire spark during TEST 1, there's a strong chance that:
- The distributor cap is faulty.
- The spark plug wire or wires that didn't spark are no good.
We'll figure it out by testing for spark straight from the distributor cap towers that feed those wires.
Like you see in the photo above, pull the spark plug wire off its tower on the distributor cap, and plug your spark tester into that tower instead.
Have your assistant crank the engine while you watch the spark tester.
If you see the spark tester sparking, that means the spark plug wire connected to that tower (and that didn't fire earlier) is the problem —swap it out and all the others with a new set.
If there's no spark at the tester, then the distributor cap is the issue and the reason why that wire failed TEST 1.
Alright, here's how to run the test:
- 1
Take off the spark plug wire (the one that didn't spark) from its tower on the distributor cap.
- 2
Insert the spark tester directly into that tower (check the photo above for reference).
- 3
Use a jumper cable to Ground the spark tester by hooking it to the battery's negative (-) terminal.
- 4
Have your helper crank the engine while you keep an eye on the HEI spark tester.
- 5
You should see the tester spark.
- 6
If there are other towers that didn't produce spark in TEST 1, repeat this process on each of them.
Now let's break down what your results mean:
CASE 1: You saw a spark. That's the result you want —it tells you the spark plug wire connected to that tower is the problem. Time to replace the entire set of spark plug wires.
That should clear up the misfire issue. And if the distributor cap and rotor are just as old as those wires, it's a smart move to replace them too.
Why it matters: Spark plug wires wear out. Over time, they build up resistance and stop carrying spark properly. That can lead to misfires, sluggish performance, or even a no-start problem.
CASE 2: You got no spark. That means the distributor cap is the issue —it's not sending spark through that tower like it should.
A new distributor cap and rotor should fix the misfire. And again, if the wires and spark plugs are just as old, go ahead and swap those out too.
Why? The terminals inside the cap (where the wires plug in) eventually corrode. That corrosion builds up resistance, and once it gets bad enough, it stops the spark from reaching the wires —killing ignition to that cylinder.