TEST 2: Checking For Spark Directly On The Distributor Cap
IMPORTANT: If you got no spark from all of the spark plug wires in TEST 1, you're next step is to go to: TEST 3: Checking The Ignition Coil High Tension Wire For Spark.
If you've reached this test section, you've got one or more spark plug wires that did not spark in TEST 1. What we'll do now is check for spark directly on the distributor cap towers of those wires (that did not spark).
In this way, we'll indirectly check the spark plug wire to determine if it's good or bad. To be a bit more specific, if the spark tester sparks while connected to the spark plug wire's tower, you can conclude that the spark plug wire is bad.
If the tower does not spark, then we can conclude that the distributor cap is bad.
Let's get started:
- 1
Remove the spark plug wire that did not spark from its tower on the distributor cap.
- 2
Place the spark tester directly on the tower (see the photo above).
- 3
Connect the spark tester to the battery negative (-) terminal with a battery jump start cable.
NOTE: The battery jump start cable will also aid you in holding the spark tester in place on the distributor cap. - 4
Have your assistant crank the engine while you observe the spark tester.
- 5
The spark tester should spark the entire time the engine is cranking.
- 6
Repeat this test on the other distributor cap towers whose spark plug wire did not fire off spark (if applicable).
Let's take a look at what your test results mean:
CASE 1: You got spark from the distributor cap tower. This result lets you know that the distributor cap is good and that the spark plug wire that did not spark is bad. Replace all of the spark plug wires as a set.
Here's why: As the spark plug wire ages, its normal resistance to spark increases to the point that the wire can not and does not transmit the spark to the spark plug. This will either cause a misfire, or a lack of power, or a no-start condition. Spark plug wires don't last forever, especially after-market ones (average life-span is 3 to 4 years).
CASE 2: You got NO spark from the distributor cap tower. With this test result you can conclude the distributor cap is bad and needs to be replaced.
Here's why: As the distributor cap ages, the terminals that transmit the spark to the spark plug wires corrode. This corrosion increases the resistance to spark and over time (as more corrosion is created) this same corrosion stops the spark from passing thru' to the spark plug wires.
If the spark plug wires are as old as the ignition coil, I recommend replacing them too.
TEST 3: Checking The Ignition Coil High Tension Wire For Spark
If all of the spark plug wires did not fire spark in TEST 1, the next step is to see if spark is actually being delivered to the distributor cap.
What we'll do is attach the spark tester to the ignition coil's high tension wire (on the end that connects to the distributor cap) as shown on the photo above.
If the ignition coil's high tension wire spark, we can conclude that the distributor cap and rotor are bad (and behind the no-spark test result in TEST 1).
If the high tension wire does not spark, our next step is to check for spark directly on the ignition coil's tower (TEST 4).
CAUTION: You'll be working around a cranking engine, so be careful and take all necessary safety precautions.
These are the test steps:
- 1
Disconnect the ignition coil's high tension wire from the center of the distributor cap
IMPORTANT: Leave the other end of the high tension wire connected to the ignition coil. - 2
Attach the HEI spark tester to the high tension wire (see the photo above).
IMPORTANT: Make sure that the metal terminal that fits into the distributor cap tower (and that is now exposed) does not come in close proximity to any metal part of the engine or the spark will arch to Ground instead of jumping across the spark tester's air gap. - 3
Connect the HEI spark tester to the battery negative (-) post with a battery jump start cable.
- 4
Ask your helper to crank the engine as you watch the spark tester.
- 5
The spark tester should spark the entire time the engine is cranking.
Let's take a look at what your test results mean:
CASE 1: You got spark. This is the correct and expected test result.
This test result confirms that the ignition coil and its high tension wire are OK. You can conclude that the distributor cap and distributor rotor are bad if you have:
- Confirmed that all six spark plugs are not sparking (TEST 1).
- Confirmed that the ignition coil's high tension wire spark (this test section).
CASE 2: You got NO spark. Your next step is to check for spark directly on the ignition coil's tower. For this test go to: TEST 4: Checking For Spark Directly On The Ignition Coil Tower.
TEST 4: Checking For Spark Directly On The Ignition Coil Tower
So far, you have confirmed that:
- None of the spark plug wires are sparking (TEST 1).
- The ignition coil's high tension wire is not sparking (TEST 3).
We're now gonna check for spark directly on the ignition coil's tower. If the spark tester sparks on the ignition coil tower, we can conclude that the coil's high tension wire is bad and is causing the engine not to start.
If the spark tester does not spark, then our next step is to make sure the ignition coil is getting power (in TEST 5).
Let's get started:
- 1
Remove the high tension wire from the ignition coil's tower.
- 2
Place the spark tester in the ignition coil's tower (see the photo above).
- 3
Connect the spark tester to the battery negative (-) terminal with a battery jump start cable.
NOTE: The battery jump start cable will also aid you in holding the spark tester in place on the distributor cap. - 4
When ready, ask your helper to crank the engine as you observe the spark tester.
- 5
The spark tester should spark the whole time the engine is cranking.
Let's take a look at what your test results mean:
CASE 1: You got spark. This is the correct and expected test result.
You can conclude that the spark plug wire (that connects the ignition coil to the distributor cap) is bad and needs to be replaced if you have:
- Confirmed that none of the spark plug wires are sparking (TEST 1).
- Confirmed that the ignition coil's high tension wire is not sparking (TEST 2).
Replace all of the spark plug wires as a set. If the distributor cap and rotor are as old as the spark plug wires, replace them too.
CASE 2: You got NO spark. Your next step 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
