TEST 1: Testing For Spark At The Spark Plug Wires

Power Transistor Test and Ignition Coil Test (1990, 1991, 1992, 1993, 1993, 1994, 1995 3.0L Nissan Pathfinder, D21, And Pick Up)

Whether you're trying to diagnose a no-start problem or a misfire problem I suggest that you test all 6 spark plug wires for spark with a spark tester.

Now, if you have already made sure that there is no spark from any of the six spark plug wires, then your starting point is TEST 3: Testing The Ignition Coil's High Tension Wire For Spark.

These are the test steps:

  1. 1

    Disconnect the spark plug wire from its spark plug.

  2. 2

    Attach the HEI spark tester to the spark plug wire (see the photo above).

  3. 3

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

  4. 4

    Have your assistant crank the engine while you observe the spark tester. If you're testing a misfire condition, the engine will start so be careful.

  5. 5

    You're going to see only one of two results: the spark tester will spark or it won't spark.

  6. 6

    Repeat the spark test on the remaining spark plug wires.

Let's take a look at your test results:

CASE 1: All spark plug wires have spark. This is the correct and expected test result.

This result let's you know that the power transistor, ignition coil, camshaft position sensor, distributor rotor and cap, and spark plug wires are OK.

If your Nissan's 3.0L V6 engine is misfiring, take a look at the suggestions found here: Other Causes Of A Misfire.

CASE 2: All spark plug wires have NO spark. The next step is to check that the ignition coil's high tension wire is delivering spark to the distributor cap.

For this test go to: TEST 3: Testing The Ignition Coil's High Tension Wire For Spark.

CASE 3: Some but not all of the spark plug wires sparked. The next step is check for spark directly on the distributor cap towers that feed spark to the wires that did not fire off spark. For this test go to: TEST 2: Testing For Spark At The Distributor Cap.

TEST 2: Testing For Spark At The Distributor Cap

Testing For Spark At The Distributor Cap. Power Transistor Test and Ignition Coil Test (1990, 1991, 1992, 1993, 1993, 1994, 1995 3.0L Nissan Pathfinder, D21, And Pick Up)

It's common for individual spark plug wires to fail. When this happens the bad spark plug wire does not transmit spark (from the distributor cap to the spark plug).

To find out if the spark plug wire (that did not spark in TEST 1) is bad, we're gonna' test for spark directly on its distributor cap tower (see photo above).

If the spark tester sparks (when connected directly on the distributor cap tower) then you can conclude that the spark plug wire is bad.

If the spark tester does not spark then you can conclude that the distributor cap is bad and needs to be replaced.

These are the test steps:

  1. 1

    Remove the spark plug wire (that did not spark) from its tower on the distributor cap.

  2. 2

    Place the spark tester directly on the tower (see photo above).

  3. 3

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

  4. 4

    Ask your helper to crank the engine while you observe the HEI spark tester.

  5. 5

    The spark tester should spark.

  6. 6

    Repeat this test on the other distributor cap towers that did not spark (if applicable).

Let's analyze your test results:

CASE 1: You got spark. This is the correct test result and it confirms that the spark plug wire (that did not spark in TEST 1) that connects to that tower is bad, replace all of the spark plug wires as a set.

Replacing the spark plug wires will solve your misfire condition. Now, if the rest of the distributor components (distributor cap and rotor) are as old as the spark plug wires then I recommend that you replace them too.

Here's why: As the spark plug wire gets older (they usually have a service life 3 to 4 years), its normal resistance to spark increases to the point that it can't and doesn't channel spark to the spark plug. This will either cause a misfire, or a lack of power, or a no start condition.

CASE 2: You got NO spark. This test result confirms that the distributor cap is bad.

Replace the distributor cap and distributor rotor as a set. This should solve your misfire problem. Now, if the rest of the distributor components (spark plug wires and spark plugs) are as old as the distributor cap and rotor then I recommend that you replace them too.

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 will stop the transmission of spark to the spark plug wires.

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

Testing The Ignition Coil's High Tension Wire For Spark. Power Transistor Test and Ignition Coil Test (1990, 1991, 1992, 1993, 1993, 1994, 1995 3.0L Nissan Pathfinder, D21, And Pick Up)

The ignition coil's high tension wire can fail and if it has failed, then your 3.0L V6 Nissan Pathfinder (D21, or Pick Up) won't start due to a lack of spark.

To be a bit more specific, when the ignition coil's high tension wire fails then none of the six spark plug wires will spark and the engine will crank but not start.

To find out if the ignition coil's high tension wire is bad, we're gonna' connect the spark tester to the end that connects to the distributor cap (just like it's shown in the photo above).

If the ignition coil's high tension wire sparks then you can conclude that it's good and that the distributor cap is bad.

If the ignition coil does NOT spark then the next step is to check for spark directly in the ignition coil's tower in TEST 5.

NOTE: You may need to use a small piece of electrical tape to secure the spark tester to the high tension wire's metal terminal. In the photo above I'm not using any black electrical tape to secure the spark tester to the terminal.

Let's get testing:

  1. 1

    Disconnect the high tension wire that connects to the center of the distributor ca.

    This wire is the high tension wire that connects the igntion coil to the distributor cap.

  2. 2

    Place the HEI spark tester directly on the ignition coil high tension wire's metal terminal.

    You may need to use a small piece of black electrical tape to secure the spark tester to the wire's metal terminal.

    NOTE: You'll connect the spark tester to the end of the wire that connects to the center tower of the distributor cap. The other end of the wire remains connected to the ignition coil.

  3. 3

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

  4. 4

    Have your helper crank the engine as you hold the HEI spark tester above the engine.

  5. 5

    The spark tester should spark.

Let's analyze your test results:

CASE 1: The spark tester sparked. This is the correct test result.

You can conclude that the distributor cap is bad only if you have:

  1. Confirmed that all of the spark plug wires are not sparking (TEST 1).
  2. Confirmed that the ignition coil's high tension wire does spark (TEST 3).

Replacing the distributor cap and rotor as a set should solve the no-start problem on your 3.0L V6 Nissan Pathfinder (D21 or Pick Up).

CASE 2: The spark tester DID NOT spark. Then the next step is to check for spark directly on the ignition coil's tower. For this test go to: TEST 4: Testing The Ignition Coil For Spark.