TEST 4: Testing The Ignition Coil For Spark
If you've reached this point, TEST 1 and TEST 3 have confirmed that:
- The eight spark plug wires are not sparking (TEST 1).
- The ignition coil's high tension wire is not sparking (TEST 3).
Now you're gonna' check for spark directly on the ignition coil's tower, as shown in the photo above.
If you get spark, then you can conclude that the ignition coil's high tension wire is bad and that it has stopped transmitting spark to the distributor cap (this happens a lot). The end result is a no-spark/no-start problem.
If you don't get spark from the ignition coil's tower, then your next step is to go to TEST 5.
These are the test steps:
Disconnect the high tension wire that connects to the ignition coil.
Connect the spark tester to the ignition coil's tower (see photo above).
Ground the spark tester directly on the battery negative (-) terminal with a jump start cable.
Have your helper crank the engine.
The spark tester should spark.
Let's examine your test result:
CASE 1: The spark tester sparked. This is the correct test result.
This test result let's you know that the ignition coil is good. You can also conclude that the ignition coil's high tension wire is bad if you have:
- Confirmed that none of the spark plug wires have spark in TEST 1.
- Confirmed that the ignition coil's high tension wire did not spark in TEST 3.
- Confirmed in this test section that the ignition coil does spark.
CASE 2: The spark tester DID NOT spark. The next test is to make sure that the ignition coil is getting 10 to 12 Volts.
For this test go to: TEST 5: Making Sure The Ignition Coil Is Getting 12 Volts.
TEST 5: Making Sure The Ignition Coil Is Getting 12 Volts
We're now gonna' make sure that the ignition coil is getting 10 to 12 Volts.
The wire that supplies this voltage is the grey with black stripe (GRY/BLK) wire and it connects to the terminal on the ignition coil labeled with a (+) symbol. This wire is labeled with the number 1 in the photo above.
We'll use a multimeter to check for these 10 to 12 Volts while cranking the engine.
CAUTION: To check for the presence of 12 Volts you must crank the engine. Be careful and take all necessary safety precautions!
These are the test steps:
Select Volts DC mode on your multimeter.
Connect the red multimeter test lead to the ignition coil's terminal labeled with the (+) symbol.
NOTE: You don't need to disconnect the wire from the terminal.
Connect the black lead of the multimeter to the battery (-) negative terminal.
Have your helper crank the engine while you observe the multimeter.
You should see 10 to 12 Volts on the multimeter.
Let's analyze your test result:
CASE 1: 10 to 12 Volts are present in the GRY/BLK wire. This is the correct test result and it tells you that the ignition coil is getting power.
Since we're diagnosing a no-spark/no-start problem, the next step is to check that the ignition coil is receiving an activation signal. Go to: TEST 6: Testing The Ignition Coil's Activation Signal.
CASE 2: 10 to 12 Volts ARE NOT present in the GRY/BLK wire. If the ignition coil doesn't get power, it will not fire spark.
This lack of spark will be caused by one of the following:
- An open-circuit problem in the GRY/BLK wire between the ignition coil's connector and the auto shutdown relay (ASD) relay.