TEST 3: Testing The Ignition Coil's High Tension Wire

How To Test A Misfire / No Spark-No Start Condition (4.3L, 5.0L, 5.7L 96-04)

If you've reached this point, then your test results confirm that none of the spark plug wires are sparking.

So in this step you'll test the spark plug wire (high tension wire) that feeds the spark to the distributor (from the ignition coil) to see if it is bad or if the distributor cap is bad.

If either the ignition coil's high tension wire or distributor cap is bad, then you'll have a no spark/no start problem.

Let's get started:

  1. 1

    Remove the spark plug wire that is attached to the center of the distributor cap.

    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

    Attach the HEI spark tester to this wire.

  3. 3

    Ground the HEI spark tester to the battery negative (-) terminal with a battery jump start cable.

  4. 4

    Ask your helper to crank the engine while you watch for spark jumping across the air gap of the spark tester.

  5. 5

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

Let's analyze each result in more detail below:

CASE 1: The spark tester sparked. This is the correct test result and it confirms that the ignition coil's high tension wire is good and that the ignition coil itself is also good.

By a process of elimination these tests confirm that the distributor cap is bad. Replace the distributor cap and rotor as a set and your no start condition should be solved.

CASE 2: The spark tester DID NOT 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.

We're gonna' find out with the rest of the tests, go to: TEST 4: Spark Test At Ignition Coil Tower.

TEST 4: Spark Test At Ignition Coil Tower

How To Test A Misfire / No Spark-No Start Condition (4.3L, 5.0L, 5.7L 96-04)

So far, in all of your tests, you have gotten a no spark result on everything you have tested. Now, you're gonna' test for spark directly on the ignition coil's tower.

If you get spark, then you can conclude that the ignition coil's high tension wire is bad and is the cause of the no spark test results you got in TEST 1 and TEST 3.

If you DO NOT get spark, then the next step is to see if the ignition coil is getting 10 to 12 Volts in TEST 5.

These are the test steps:

  1. 1

    Remove the spark plug wire that's attached to the ignition coil's tower (as shown in the photo above).

  2. 2

    Now, connect the HEI spark tester to the coil's tower with a small piece of vacuum hose (this is important!, look at the photo to see how I've done it).

  3. 3

    Ground the HEI spark tester with a battery jump start cable (who's other end is grounded on the engine or battery negative post).

  4. 4

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

  5. 5

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

Let's your spark test result below:

CASE 1: You got spark. Then the spark plug wire that feeds the distributor cap spark is bad and the ignition coil is GOOD. Replace the spark plug wire by replacing All of the spark plug wires.

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. The 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. Then further testing is required to see if the problem is due to a bad ignition control module (ICM), bad pick up coil or something else.

We're gonna' find out with the rest of the tests, go to: TEST 5: Testing The Ignition Coil For 12 Volts.

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  • Astro
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Blazer
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Blazer TrailBlazer
    • 1999, 2000, 2001
Chevrolet Vehicles:
  • C1500, C2500, C3500 Pick Up
    • 1996, 1997, 1998, 1999, 2000
  • Express Van 1500, 2500, 3500
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
  • G30 Van
    • 1996
  • K1500, K2500, K3500 Pick Up
    • 1996, 1997, 1998, 1999, 2000
Chevrolet Vehicles:
  • K1500, K2500 Suburban
    • 1996, 1997, 1998, 1999
  • P30 Van
    • 1996, 1997, 1998, 1999
  • S10 Blazer
    • 1994
  • S10 Pick Up
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
Chevrolet Vehicles:
  • Silverado 1500 Pick Up
    • 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007
  • Tahoe
    • 1996, 1997, 1998, 1999, 2000
GMC Vehicles:
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    • 1996, 1997, 1998, 1999, 2000
GMC Vehicles:
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    • 1996, 1997, 1998, 1999
  • G3500 Van & Vandura
    • 1996
  • Jimmy & Envoy
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • K1500, K2500, K3500 Sierra
    • 1996, 1997, 1998, 1999, 2000
GMC Vehicles:
  • P3500 Van
    • 1996, 1997, 1998, 1999
  • S15 Jimmy
    • 1994
  • Safari
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
GMC Vehicles:
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    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
  • Sonoma
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
GMC Vehicles:
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    • 1996, 1997, 1998, 1999, 2000, 2001, 2002
Isuzu Vehicles:
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    • 1997, 1998, 1999, 2000
Oldsmobile Vehicles:
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    • 1996, 1997, 1998, 1999, 2000, 2001
Cadillac Vehicles:
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