TEST 1: Testing For Spark

Testing For Spark. How To Test The COP Coils (GM 4.8L, 5.3L, 6.0L, 8.1L)

This a pretty straight forward test, but one that has to be done with the HEI spark tester. Here are a couple of friendly reminders that'll help you to avoid wasting money and time (by not replacing a good part):

  1. Do not use a regular spark plug instead of a dedicated spark tester. The result you may get from using a regular spark plug IS NOT trustworthy.
  2. Do not pull the ignition coil off of its spark plug, as the engine is running, to see/hear if it's sparking. This method can ruin/fry the ignition coil and now you've got another problem on your hands.
  3. I don't recommend using any other type of spark tester. Buy the HEI spark tester... not an imitation or something similar.

OK, now on with the show, If you know which cylinder is the one misfiring, start here. If you don't know, then I suggest that you test all of the COP coils for spark, start here also. Alright then, the very first thing that has to be done is to:

  1. 1

    Remove the spark plug wire from the spark plug wire of the first Coil-on-Plug ignition coil (which one? it doesn't matter if you're gonna' test them all) that you're gonna' test.

    Attach the HEI spark tester (or an equivalent spark tester) to the Coil-on-Plug ignition coil (as shown in the photos in the image viewer).

  2. 2

    Attach the HEI spark tester to a good Ground point by using a battery jump start cable (my preferred method).

  3. 3

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

    If all is OK, your spark tester should spark.

  4. 4

    Repeat the test for all of the remaining Coil-on-Plug ignition coils (if you're testing them all).

Let's take a look at what your test results mean:

CASE 1: If you got spark, from the Coil-on-Plug ignition coil, then the ignition coil is OK. The cause of the misfire is something else. Go to: TEST 8: Carbon Tracks and Other Stuff.

CASE 2: If you got NO spark, the next step is to bypass the spark plug wire and test for spark directly on the Coil-on-Plug ignition coil. For this test go to: TEST 2: Testing For Spark Directly At The COP Coil.

TEST 2: Testing For Spark Directly At The COP Coil

Testing For Spark Directly at the COP Coil. How To Test The COP Coils (GM 4.8L, 5.3L, 6.0L, 8.1L)

It's possible that the spark plug wire, that's attached to the COP ignition coil, could be BAD.

To prove this, you need to remove the spark plug wire from its COP ignition coil and test for spark directly on the COP coil tower. This test will either eliminate or condemn the spark plug wire as good or BAD.

These are the test steps:

  1. 1

    Remove the spark plug wire (also known as the High Tension Wire) that did not spark from its spark plug.

    Attach the HEI spark tester directly to the Coil-on-Plug (COP) ignition coil's tower (as shown in the photos in the).

  2. 2

    Attach the HEI spark tester to a good Ground point by using a battery jump start cable.

    Your spark tester should spark.

  3. 3

    Repeat the test for all of the remaining Coil-on-Plug ignition coils whose spark plug did not fire off spark in TEST 1 (if applicable).

Let's take a look at what your test results mean:

CASE 1: If you got spark, then the COP ignition coil is good and the spark plug wire (high tension wire) is BAD. Replacing the spark plug wires (as a set) should solve the misfire condition or misfire code that's lighting up your check engine light (CEL) on your instrument cluster.

As a side note, if your GM (or Hummer or Isuzu Pick Up or Van or SUV) has over 100,000 miles, I recommend that you replace all of the spark plugs also (for preventive maintenance sake).

CASE 2: If you got NO spark, the next step is to verify that this specific Coil-on-Plug ignition coil is receiving 12 Volts, Ground, and its Triggering signal from the PCM. Go to: TEST 3: Testing The Power Circuit (12 Volts).