How To Check for Spark When an Engine Does Not Start

By | November 2, 2022

How To Check for Spark When an Engine Does Not Start
If you find yourself with a vehicle where the engine does not start, the first things to check are the spark and gas.

All mechanics will eventually find themselves with this problem and need to diagnose the electrical problem.

Knowing whether an engine has a spark will quickly help narrow the problem with a vehicle that does not want to start.

What is Engine Spark?

What is Engine Spark
The heart of a combustible engine is gas for fuel and a spark to ignite it.

Gas is fed into a combustible chamber, and a spark is fired to set it off, creating a small controlled explosion.

These small explosions send a piston downward, driving a crankshaft and a running engine.

While engines, especially new ones, can be complex, this basic combination of fuel and spark is what makes any engine run.

Checking if an engine is getting a spark can quickly rule out or point to the part of a vehicle that has a problem.

The first step when fixing any engine is troubleshooting the problem and narrowing it down to the bad part in steps.

Tools Needed to Test an Engine for Spark

Tools Needed to Test an Engine for Spark
There is a way to test for spark without using a tool, but a spark plug testing tool makes the job much easier.

A spark plug tool also reduces the risk of a shock from the coil high voltage.

With that said, I have tested for spark many times with no spark plug testing tool, but they are low-cost items that make the job much easier.

If you do not have the tool, the spark plug will need to be removed with the tip held close to a ground, such as the engine block, to see if a small spark flashes.

How To Check for Spark on an Engine

  1. Locate the spark plugs and remove one of the spark plug wires.
  2. How To Check for Spark on an Engine Step 1

  3. Insert the spark plug wire into a spark plug testing tool.
  4. How To Check for Spark on an Engine Step 2

  5. Insert the other side into the spark plug hole.
  6. How To Check for Spark on an Engine Step 3

  7. The indicator light will flash rapidly if there is a spark.
  8. How To Check for Spark on an Engine Step 4

  9. If there is no spark the light will not flash.

Checking an engine for spark is necessary for troubleshooting and a common test when an engine does not start.

If there is a spark, it doesn’t completely rule out a spark problem, but in most cases, there will be another issue.

If there is no spark, each component will need to be tested to see which part is causing the issue.

Older cars and trucks are much simpler to troubleshoot with a coil, distributor, rotor, possibly points, spark plug wires, and ignition hot wire, the main components to test.

New cars and trucks have different systems to manage parts with coil packs, spark plug wires, fuses, cam sensors, and crankshaft sensors the first things to look at.

Of course, every manufacturer is different and may have designed things differently.

While there may be different systems, most all vehicle engines can be tested for spark the same way.


Category: General Automotive Repair

About Bob Thomas

Bob Thomas is an automotive mechanic with 30 plus years experience. He is a contributor to several publications and has written many articles on automotive maintenance and repairs. He also has created many auto repair videos on YouTube.

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