How To Test The Ignition Coil (1988-1993 4.3L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma)

In this tutorial, I'll explain how to easily and quickly check the ignition coil on your vehicle using only a few simple tools.

To make it even easier, I've broken down the process into four simple tests, each with step-by-step instructions to help you determine if the ignition coil is the source of your engine's no-start problem.

APPLIES TO: This tutorial applies to the following vehicles:

• 4.3L Chevrolet S10 Pickup: 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995.
• 4.3L GMC S15 Pickup: 1988, 1989, 1990.
• 4.3L GMC Sonoma: 1992, 1993, 1994, 1995.

Symptoms Of A Bad Ignition Coil

An engine no-start problem is the most common symptom of a faulty ignition coil. More precisely, you turn the key and the engine cranks but does not start.

This is because when the ignition coil fails, it can no longer provide the spark that the spark plugs need to ignite the fuel in the engine.

The cool thing is that testing the ignition coil isn't difficult at all, and in the subheadings below I explain how.

Ignition System Diagnostic Manual Download

While this tutorial is a great resource, it doesn't include everything you need, such as a wiring diagram or a complete testing procedure in one place.

The digital download manuals (in PDF format that you can print) below include all this and more at an affordable price that won't break the bank. With this diagnostic manual, you'll have all the info you need to diagnose an engine no-start problem or an engine misfire problem caused by the ignition system. Order now and solve it today!

Where To Buy The ignition Coil And Save

The ignition coil isn't an expensive ignition system component and you can pretty much buy it anywhere.

The important thing to remember when buying an ignition coil is to buy a brand name component. The original equipment manufacturer is AC Delco.

The following ignition coils are from known Automotive brand names.

Ignition Coil Connector Circuit Descriptions

GREY CONNECTOR
Terminal	Wire	Description
A	White (WHT)	Tach signal output
B	Pink (PNK)	12 Volts (input from ignition switch)

BLACK CONNECTOR
Terminal	Wire	Description
C	White (WHT)	IC control signal
D	Pink (PNK)	12 Volts (output to ICM)

Ignition System Basics

The ignition system of your 4.3L Chevrolet S10 pickup (GMC S15 pickup, GMC Sonoma) is a simple mechanical distributor ignition system consisting of the following components:

• An ignition coil.
• A mechanical distributor.
• An ignition control module.
• A pickup coil (CKP sensor).
• Spark plug wires.
• Spark plugs.

In a nutshell this is how the ignition system works:

1. The ignition coil receives 12 Volts from the pink (PNK) wire that connects to the gray connector terminal labeled with the letter B.
2. The 12 Volts that enter the ignition coil are then sent to the ignition module through the PNK wire of the black connector, which is connected to terminal D.
3. As the engine begins to crank, the pick-up coil (also known as the crankshaft position sensor) starts generating its position signals, which are then sent to the ignition control module (ICM).
4. The ICM then activates the ignition coil through the white (WHT) wire of the black connector, connected to terminal C in the illustration.
5. The ICM turns ON and OFF the Ground circuit to spark the ignition coil.
6. The performance of the ignition coil can be checked by verifying that it's receiving power and that the ICM is providing the activation signal.

TEST 1: Testing The Ignition Coil High Tension Wire For Spark

To begin the process of troubleshooting the ignition coil, it's important to determine that it's not generating spark.

This can be easily done by connecting a specialized spark tester to the high voltage wire of the ignition coil and having someone crank the engine.

If the ignition coil is functioning properly, the spark tester should spark, indicating that the coil is providing spark to the spark plugs.

NOTE: It's important to use a dedicated spark tester for this test as any other method of testing for spark can lead to misdiagnosis and wasted time and money.

Alright, these are the test steps:

1. 1

   Disconnect the high tension wire from the center tower of the distributor cap.
   
   NOTE: Leave the other end of the high tension wire attached to the ignition coil.

2. 2

   Attach the HEI spark tester to the spark plug wire.

3. 3

   Connect the spark tester to the battery negative (-) post using a battery jump start cable (see the illustration above).

4. 4

   Have your helper crank the engine while you observe the spark tester from a safe distance.

5. 5

   You'll get one of two results:
   
   1.) The spark tester will spark.
   
   2.) The spark tester will NOT spark.

Let's interpret your test results:

CASE 1: The spark tester sparked. This test result tells you that the ignition coil and its high tension wire are OK.

If the engine is not starting, you can conclude that the ignition coil and its high tension wire are not behind the problem.

CASE 2: The spark tester DID NOT spark. This test result confirms that a no-spark issue is causing the engine not to start.

The next test is to check for spark directly on the ignition coil tower. Go to: TEST 2: Testing The Ignition Coil Tower For Spark.