TEST 2: Testing For Spark At The Distributor Cap

Testing For Spark At The Distributor Cap. How To Test The Ford Ignition Control Module

If you've reached this point it's because one or two spark plug wires did not fire off spark in TEST 1.

In this test section we're now going to remove the spark plug wire that did not fire off spark and place the HEI spark tester on that wires distributor cap tower (see photo above).

This test will let us know if the spark plug wire is bad or if the distributor cap is bad (and the cause behind the failed test in TEST 1).

As you can see in the photo above, I'm using a small piece of vacuum hose to securely attach to HEI spark tester to the cap's tower

OK, this is what you'll need to do:

  1. 1

    Remove the spark plug wire that did not spark from its tower on the distributor cap and place the spark tester directly on the tower.

    I recommend you use a battery jump start cable to hold the spark tester to the tower as shown in the photo at left.

    NOTE: Also, you MUST use a small piece of vacuum hose to Attach the HEI spark tester to the cap tower being tested (see photo 2 of 2 in the image viewer).

  2. 2

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

  3. 3

    Repeat this test with the others that did not fire off spark (if applicable).

You're only gonna' get one of two results: Spark or No Spark. Let's analyze each of these results below:

CASE 1: If you got spark, Then the spark plug wire is BAD, replace them all. This is probably as far as you may need to go since your Ford car (or truck, or mini-van, or van) will probably start or solve your misfire problem after replacing these parts.

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: If you got No Spark, Then the distributor cap is BAD. Replace the distributor cap and distributor rotor as a set. This should solve your misfire problem.

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.

TEST 3: Testing For Spark At The Ignition Coil (Part 1)

Testing For Spark At The Ignition Coil (Part 1). How To Test The Ford Ignition Control Module

OK, with this test you're gonna' find out if the spark plug wire that feeds the spark from the ignition coil to the distributor is BAD or not (this is a two part test, with part two done in TEST 4).

This is a very common problem/cause of a No Start... where the spark plug wire that connects the ignition coil to the distributor cap goes BAD and stops transmitting spark. The end result is a No Start Condition.

This is what you'll need to do:

  1. 1

    Remove the spark plug wire that is attached to the center of the distributor cap and attach the HEI spark tester to this wire.

    NOTE: The other end of this spark plug wire must remain attached to the ignition coil (this is important!, look at the photo to see how I've done it).

  2. 2

    With the HEI spark tester being held with a battery jump start cable (who's other end is grounded on the engine or battery negative post), ask your helper to crank the engine once again while you watch for spark jumping across the air gap of the spark tester.

  3. 3

    You're gonna' get one of the 2 results: (1) Spark or (2) No Spark.

Let's analyze your test result in more detail below:

CASE 1: If you got spark, This result confirms that spark is being delivered to the distributor but that the distributor cap is unable to distribute the spark to the spark plug wires.

Also, this test confirms that the ignition coil is GOOD. Replace the distributor cap and rotor as a set and retest (or crank up the vehicle). This should solve your No Start Condition.

CASE 2: If you got NO spark. Then further testing is required to see if the problem is due to a BAD ignition control module (ICM), BAD ignition coil, BAD Pick Up Coil or something else.

Don't worry... with help of this step-by-step tutorial, we'll find out exactly what's wrong... right now, the next step is to check for spark directly on the ignition coil. Go to: TEST 4: Testing The Ignition Coil (Part 2).