If the ignition coil on your 2.8L Chevy S10 (GMC S15) fails, the engine is going to crank but not start due to a lack of spark. The cool thing is that testing the ignition coil is not that hard. You're going to be surprised just how easy it is to find out.
In this tutorial I'll show you how to test it in a step-by-step way without having to take it off the engine and without any expensive diagnostic test equipment.
Contents of this tutorial at a glance:
- Symptoms Of A Bad Ignition Coil.
- How Does The Ignition Coil Work?
- TEST 1: Making Sure Spark Is Missing.
- TEST 2: Testing For Spark Directly On The Coil Tower.
- TEST 3: Making Sure The Ignition Coil Has Power.
- TEST 4: Making Sure The Ignition Coil Is Getting the Activation Signal.
- Where To Buy The Ignition Coil And Save.
Puedes encontrar este tutorial en Español aquí: Cómo Probar La Bobina De Encendido (2.8L V6 GM) (en: autotecnico-online.com).
NOTE: This tutorial complements the tutorial on how to test the ignition control module (ICM). You can find the ICM test tutorial here: How To Test The Ignition Control Module (2.8L V6 GM).
Symptoms Of A Bad Ignition Coil
The most obvious symptoms of a bad ignition coil is that your 2.8L V6 Chevy S10 (GMC S15) is not gonna' start. To be a bit more specific, the engine will turn over but won't start.
This is due to the fact that the ignition coil is the component tasked with the job of creating and delivering spark to the ignition distributor. If the distributor isn't getting spark, none of the 6 cylinders will either.
Here are some more specific symptoms you'll see:
- Engine cranks but does not start.
- Both fuel injectors will be injecting fuel.
- Fuel pump is working.
How Does The Ignition Coil Work?
Even though the ignition coil on the 2.8 v6 Chevy S10 has four wires coming out of its connector, it's a component that works on 12 Volts and ground.
In this section I am going to break down how the ignition coil creates a spark in plain English (and in a step-by-step manner). This will help you to understand exactly the how and why of what we're gonna' be testing in the following pages of this tutorial.
When you turn the key and start cranking the engine, this is what happens:
- 12 Volts reach the ignition coil on the gray connector terminal labeled with the letter B (in the illustration above). The wire that connects to this terminal is a pink (PNK) wire.
- As these 12 Volts enter the ignition coil, they also exit on the pink wire of the black connector (terminal labeled with the letter D of the black connector). These 12 Volts now feed power to the ignition module.
- As the engine starts to crank, the pick-up coil (which is the defacto crankshaft position sensor) starts to generate its position signals to the ignition control module.
- The ignition control module (ICM) now starts to activate the ignition coil across the white wire of the black connector (terminal labeled with the letter C in the illustration above).
- The ICM activates the ignition coil to start sparking by turning on and off (interrupting) the Ground circuit.
- You and I can check the ignition coil by checking that it's getting power and that the ICM is supplying the ignition coil's activation signal.
To further help you ignition coil troubleshooting efforts, you can find the ignition system circuit diagram here: 1991-1993 2.8L Chevy S10 Ignition System Circuit Diagram.
Let's turn the page and get testing.