TEST 1: Testing For Spark At The Spark Plug Wire
IMPORTANT: To successfully diagnose these ignition coils or your misfire condition, do not skip from test to test on your own. Start here at TEST 1 and follow the indicated flow of test steps that each test result recommends.
OK, having said that, the most effective and logical starting point for our diagnostic and troubleshooting of the ignition coil packs on the GM 3.8L V6 equipped engines (Buick, Chevy, Olds, Pontiac), is to test for spark at the spark plug wire.
Whether you know or don't know which is cylinder is the one misfiring; I recommend that you test all six spark plug wires for spark and of course by using the recommended spark test procedure from the 'Do's and Don'ts' of the previous page. OK, here's the test:
- 1
Remove the spark plug wire from the spark plug and attach an HEI spark tester to it (don't have an HEI spark tester? Need to buy one? You can buy it here: OTC 6589 Electronic Ignition Spark Tester).
- 2
Ground the spark tester with a battery jump start cable.
- 3
When ready, have your helper crank the engine while you observe to see if the spark tester sparks or not. The engine will start, so be careful!
- 4
Once you have observed the spark tester sparking or not, have your assistant turn off the engine.
- 5
You'll get one of two results: either spark or no spark as the engine cranks.
If you get a NO SPARK result from two spark plug wires, you'll need to check to see if these two spark plug wires are connected to the same ignition coil.
OK, there are four different results that are possible from the spark test, let's interpret the results:
CASE 1: You got spark from all of the spark plug wires. This result confirms that the spark plug wires and the ignition coils are OK. The ignition system is not the cause of your misfire condition. For a few more thoughts on what could be the cause, go to: TEST 6: Other Common Misfire Causes.
CASE 2: You got NO SPARK from only one spark plug wire. The next test step is to check for spark directly at the ignition coil tower that the spark plug wire is attached to. Go to: TEST 2: Testing For Spark At The Ignition Coil Tower.
CASE 3: You got NO SPARK from two spark plug wires that are attached to the same ignition coil. The next step is to check for spark directly on the ignition coil's 2 towers, go to: TEST 3: Testing For Spark At The Ignition Coil Tower.
CASE 4: You got NO SPARK from two spark plug wires that ARE NOT attached to the same ignition coil. The next step is to check for spark directly on the tower of each of those two ignition coil's, go to: TEST 2: Testing For Spark At The Ignition Coil Tower.
TEST 2: Testing For Spark At The Ignition Coil Tower
In this test, you're gonna' check for spark directly on the ignition coil tower that had one of its two spark plug wires attached to it not fire spark in TEST 1.
With this test, you'll find out if the spark plug wires are bad or if the ignition coil pack is the one that has fried or continue to the next test.
Let's start:
- 1
Remove the spark plug wire (that did not fire off spark in TEST 1) from the ignition coil's tower it's attached to.
- 2
Attach an HEI spark tester to the ignition coil's tower with a small piece of vacuum hose as shown in the photo above.
- 3
Hold the HEI spark tester with a battery jump start cable, as shown in the photo.
- 4
Have your assistant crank the car while you observe the spark tester for spark. The engine is gonna' start, so be careful.
- 5
Once you've observed the spark tester sparking or not, have your assistant turn off the engine.
- 6
This test will give you one of two results: You'll get spark or no spark.
Lets take a look at what your test results mean:
CASE 1: You got spark. This result confirms that the spark plug wire is bad, replace the spark plug wires as a set.
This happens quite a bit, where a spark plug wire (or several) simply stop transmitting spark. This is mainly due to the fact that the spark plug wires are too old.
CASE 2: You got NO spark. This result indicates that the ignition coil is bad if the other tower is sparking. Replacing the ignition coil should solve the misfire condition.
I recommend that you do one more thing and this is to check for spark on the other tower (that belongs to the ignition coil you're testing in this test section).
If you get spark from the other tower, then this result lets you know beyond a shadow of a doubt that the ignition coil is bad.
Here's the reason why: The ignition coil gets only one signal to fire spark from both towers from the ignition control module (this is because both towers belong to the same circuit inside the ignition coil). So, if only one tower is firing off spark, there's something wrong inside the ignition coil itself.
