Troubleshooting the ignition system on the 1993-1998 5.2L V8 Jeep Grand Cherokee, to see if it's behind a misfire problem or a no-start problem, can seem difficult.
The truth of the matter is that it isn't difficult and all of the tests can be done with a few simple tools.
In this tutorial I'm gonna' show you how in a step-by-step manner. You'll be able to diagnose a misfire condition or a no-start caused by the ignition coil.
Contents of this tutorial at a glance:
- 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 Jeep Grand Cherokee Tutorials.
APPLIES TO: This tutorial applies to the following vehicles since they use the exact same ignition system components: 1993, 1994, 1995, 1996, 1997, 1998 5.2L V8 Jeep Grand Cherokee.
Ignition System Test Basics
The ignition system on the 1993-1998 5.2L V8 Jeep Grand Cherokee is a conventional distributor-based ignition system. Its main components are:
- Ignition coil.
- Distributor pickup coil (also known as the camshaft position sensor).
- Crankshaft position sensor (located on the transmission bell-housing).
- Spark plug wires (high tension wires).
- Distributor cap and rotor.
When you turn the key to crank and start the engine, this is what happens:
- The distributor pickup coil and the crankshaft position sensor start to generate and feed their signals to your Jeep Grand Cherokee's fuel injection computer.
- Once the fuel injection computer receives the pickup coil signal, it sends the ignition coil an activation signal.
- Once the ignition coil is activated by the fuel injection computer, it starts to spark.
- The ignition coil's spark is transmitted to the center of the distributor's cap by a high tension wire.
- The distributor rotor then distributes the spark to the distributor cap towers.
- 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?
There are quite a few tools you'll need to test the ignition system on your 5.2L V8 Jeep Grand Cherokee. The cool thing is that none of them are expensive.
The most important tool you're gonna' need is a spark tester. Here are my recommendations:
- An HEI spark tester
- A spark tester is a must have tool! It will help you get an accurate diagnostic test result as you test for spark. You can see an example of this tool here (and you can buy it here too): OTC 6589 Electronic Ignition Spark Tester).
- A 12 Volt automotive test light.
- 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
To get our ignition system diagnostic under way, we're gonna' make sure that the spark plug wires are sparking.
To get the most accurate test result from your ignition system tests, it's important that you test all 8 spark plug wires for spark.
It's important that you use a dedicated spark tester for your spark tests. Any spark tester will do. If you don't have one and need to buy one, then I recommend the HEI spark tester. You can find out more about it and where to buy it here: HEI Spark Tester (at: easyautodiagnostics.com).
CAUTION: The ignition system tests are done while cranking the engine. Be careful and take all necessary safety precautions.
Let's get started:
Disconnect the #1 cylinder spark plug wire from its spark plug.
Attach the HEI spark tester to the spark plug wire (see the photo above).
Connect the HEI spark tester to the battery negative (-) terminal with a jump start cable.
Have your assistant crank the engine while you observe the spark tester.
NOTE: If you're testing a misfire condition, the engine will start so be careful.
You're going to see only one of two results: the spark tester will spark or it won't spark.
Repeat the spark test on the remaining spark plug wires.
Let's examine your test results:
CASE 1: Spark is present at all eight spark plug wires. This is the correct and expected test result.
You can correctly conclude that the distributor pickup coil, the distributor rotor and cap, the ignition coil, and the spark plug wires are OK.
If you're trying to troubleshoot a misfire problem on your 1993-1998 5.2L V8 Jeep Grand Cherokee, then take a look at the suggestions found here: Other Causes Of A Misfire.
CASE 2: All spark plug wires have NO spark. The next step is to check that the ignition coil's high tension wire is delivering spark to the distributor cap.
To check for spark from the ignition coil's high tension wire go to: TEST 3: Testing The Ignition Coil's High Tension Wire For Spark.
CASE 3: Some of the spark plug wires (but not all) have NO spark. 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.