How To Test Hei Distributor

How to Test a HEI Distributor: A Comprehensive Guide

The High Energy Ignition (HEI) distributor is a crucial component in your vehicle's ignition system, responsible for precisely timing the spark plugs' firing sequence. A malfunctioning HEI distributor can lead to a range of problems, from poor engine performance to complete engine failure. Knowing how to test your HEI distributor can save you time, money, and frustration. This guide will walk you through various testing methods, empowering you to diagnose issues efficiently.

Understanding the HEI Distributor's Function

Before diving into testing, let's briefly review the HEI distributor's role. The HEI system, unlike older ignition systems, incorporates its own ignition coil and electronic control module within the distributor itself. This self-contained design simplifies the system and improves reliability. The HEI distributor performs these key functions:

• Generating High Voltage: The internal coil generates the high voltage needed to ignite the air-fuel mixture in the combustion chambers.
• Distributing the Spark: It distributes this high voltage to each spark plug in the correct firing order.
• Precise Timing: The distributor's internal mechanisms ensure the spark is delivered at the optimal time for efficient combustion.

Tools and Materials You'll Need

Before you begin testing, gather these essential tools:

• Test Light: This inexpensive tool is invaluable for checking for voltage and continuity.
• Ohmmeter (Multimeter): This tool measures electrical resistance, crucial for checking the internal components of the HEI distributor.
• Spark Plug Wires: Ensure these are properly connected to avoid misinterpreting test results.
• Wrench (socket or open-end): Needed to access the distributor cap and possibly remove the distributor.
• Safety Glasses: Always protect your eyes when working with electrical components.

Step-by-Step HEI Distributor Testing

We'll explore different approaches to testing your HEI distributor, ranging from simple visual inspections to more in-depth electrical tests.

1. Visual Inspection: The First Line of Defense

Start by performing a thorough visual inspection of your HEI distributor. Look for:

• Cracks or Damage: Check the distributor cap for cracks, damage, or worn contacts. A damaged cap can lead to misfires or complete ignition failure.
• Corrosion: Examine the terminals and connections for corrosion. Clean them with a wire brush or contact cleaner if necessary.
• Rotor Condition: Inspect the rotor for wear or damage. A worn rotor can hinder proper spark distribution.

2. Testing the Ignition Coil

The HEI distributor's integrated ignition coil is a common point of failure. Here's how to test it:

• With the Ohmmeter: Disconnect the coil wires from the distributor. Measure the resistance across the primary coil terminals (usually marked "P" or "+" and "-"). Compare your reading to the manufacturer's specifications found in your vehicle's repair manual. A reading outside the specified range indicates a faulty coil.
• Testing Secondary Resistance: Similarly, measure the resistance across the secondary coil terminals (usually marked "S" or "C"). Again, compare this reading to the manufacturer's specifications.

3. Checking for Spark

The simplest test is to check if the distributor is producing spark.

• Connect a Spark Plug: Attach a spark plug to one of the spark plug wires. Ground the spark plug's metal shell to the engine block.
• Inspect for Spark: Have someone crank the engine while you observe the spark plug. A strong, consistent spark indicates a properly functioning distributor. A weak or absent spark suggests a problem.

4. Advanced Testing with a Multimeter

If the simpler tests don't pinpoint the problem, more advanced testing using a multimeter is necessary. This will involve checking the pickup coil and other internal components. Consult your vehicle's repair manual for specific resistance values and testing procedures. This step often requires a deeper understanding of automotive electrical systems.

Troubleshooting Common Issues

Once you've identified a problem, troubleshooting will guide you to a solution. Common issues and solutions include:

• Weak or No Spark: This often points to a faulty ignition coil, rotor, cap, or a problem within the distributor's electronic control module.
• Intermittent Misfires: This could be due to a failing ignition coil, a cracked distributor cap, or worn rotor contacts.
• Engine Cranks but Doesn't Start: A common cause is a faulty HEI distributor. A complete diagnostic test is recommended.

When to Seek Professional Help

If you're uncomfortable performing these tests or are unable to resolve the issue, it's always best to seek help from a qualified mechanic. Improper diagnosis and repair can cause further damage to your vehicle.

By systematically working through these steps, you'll be able to effectively test your HEI distributor and pinpoint the source of any ignition problems. Remember safety first – always disconnect the battery before working on any electrical components. Happy wrenching!