How To Diagnose An Engine No-Start Problem (1988-1995 4.3L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma)

It can be extremely frustrating when the engine won't start, and unfortunately, there are several possible causes of an engine no-start problem.

Some of the most common causes are problems with the ignition coil, ignition control module, fuel pump, a blown head gasket, or even an engine compression issue.

However, identifying the root cause of the engine no-start problem is not an impossible task, if you have a clear understanding of how to test and troubleshoot these various components.

In this tutorial, I'll guide you through the process of diagnosing the issue by explaining how to test each component, one by one.

By the end of this tutorial, you should be able to confidently identify the cause of the engine no-start problem and take the necessary steps to fix it.

NOTE: Both the TBI and CPI equipped 4.3L engines are covered by this tutorial.

APPLIES TO: This tutorial applies to the following vehicles:

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

Difference Between A No-Start And A No-Crank Condition

Before we dive into the troubleshooting process, it's essential to have a clear understanding of the difference between an engine not starting (no-start) and an engine not cranking (no-crank).

Knowing the difference is critical to speeding up your diagnostic process and making it easier to identify the root cause of the problem, saving time and avoiding headaches or frustration.

Here's a simple explanation of the difference between the two: In an engine no-start situation, you turn the key, and the engine cranks but does not start.

The fact that the engine cranks tells you that the starter motor is working. Since the engine won't start, you can conclude that there's a problem with one or more of the components required to start the engine, such as: spark, fuel or compression.

On the other hand, in a no-crank scenario, you turn the key, but nothing happens - the starter motor does not come out to play, and the engine does not crank (turn over).

An engine no-crank issue is most commonly caused by a faulty starter motor or a dead battery.

If your 4.3L V6 Chevrolet S10 pickup (GMC S15 pickup, GMC Sonoma) is experiencing an engine no-crank problem, you should start your troubleshooting efforts by testing the battery and/or the starter motor.

• How To Test The Starter Motor (1988-2003 4.3L V6 Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).

Engine No-Start Diagnostic Basics

An engine requires three critical components to start:

1. Air.
2. Fuel.
3. Spark.

If your 4.3L V6 Chevrolet S10 pickup (GMC S15 pickup, GMC Sonoma) won't start, the engine may not be getting fuel from the fuel pump, not getting spark from the ignition system, or not producing compression (which is the air component).

The cool thing is that we can perform several basic tests that will help identify the root cause of the engine starting problem and determine the necessary steps to resolve it. These are:

• An ignition system test.
• A fuel system test.
• An engine compression test.
• A blown head gasket test.

In the following sections, I'll walk you through the step-by-step process of testing these components, which I use when diagnosing an engine no-start problem.

With this test information, you'll gain a better understanding of the diagnostic process to confidently identify the source of your vehicle's starting problem and take the necessary action to get it back up and running again.

What Tools Do I Need?

You'll need a few basic tools to get to the bottom of what's causing the engine not to start.

These tools are:

• A spark tester.
• A fuel pressure tester.
• An engine compression tester.
• A multimeter.
• A code reader.

To confirm that the ignition system is generating and supplying spark to the spark plugs, I recommend using an HEI spark tester.

The HEI spark tester is one of the most reliable spark testers on the market, easy to use and is reasonably priced. You can find out more about it and where to buy it here: HEI Spark Tester.

Although I didn't include a scan tool in the list, having one is a plus. But you don't need one to follow any of the suggested tests in this tutorial.

STEP 1: Testing The Ignition System For Spark

The ignition system on your 4.3L V6 Chevy S10 pickup (GMC S15 pickup, GMC Sonoma) is a distributor-based ignition system, which is responsible for distributing a high-voltage spark to the individual cylinders of the engine.

The ignition system consists of the following components:

• Ignition coil.
• Ignition control module (ICM).
• Distributor cap.
• Distributor rotor.
• Distributor.
• Distributor pickup coil (CKP sensor).
• Spark plug wires.
• Spark plugs.

This system works by having the ignition coil generate a high-voltage spark that is then distributed to the spark plugs through the distributor cap and rotor and spark plug wires.

Since you're experiencing an engine no-start problem, your first step in troubleshooting the ignition system is to check all six spark plug wires to ensure that they are delivering spark to the spark plugs.

This first step is crucial in determining if the ignition system is the cause or not the cause of the engine no-start problem.

To help you with this process, the following tutorials will provide you with a systematic approach to diagnosing the ignition system, so you can determine if it's the root cause of the engine no-start problem and take the necessary actions to resolve it:

• How To Test The Ignition Coil (1988-1993 4.3L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
• ICM And Distributor Pickup Coil Tests (1988-1995 4.3L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).

The ignition system is NOT causing the no-start problem if:

• Spark is present at all six spark plug wires when cranking the engine.

If all six spark plug wires delivering spark to their spark plugs, you can conclude that the ignition system is NOT causing the engine no-start problem.

You can also conclude that:

• The distributor pickup coil (CKP sensor) is good.
• The ignition control module (ICM) is good.
• The ignition coil is good.
• The distributor cap and rotor are good.
• The spark plug wires are good.

Since the ignition system is creating and feeding spark to the engine cylinders, the next test steps are to test the fuel pump's pressure. Go to: STEP 2: Testing The Fuel Pump's Pressure.

The ignition system IS THE CAUSE of the no-start problem if:

• The six spark plug wires ARE NOT sparking.

The components that can cause this no-spark problem are:

• A bad distributor pickup coil.
• A bad ignition control module (ICM).
• A bad ignition coil.
• A bad ignition coil high tension wire.