In this guide, you will learn how to check if spark plugs are getting power.

The easiest and safest way to check for spark by yourself is to use inline spark plug tester.

Alternative methods to test an engine for spark include removing the spark plug and grounding it or testing for spark with a screwdriver.

Important

  • When you test your ignition system for spark, keep your hands off ignition coils, wires or spark plugs while cranking the engine. Ignition coils generate in average 30,000 volts enough to cause injuries and shock. 
  • If you will be cranking the engine for an extended period to test your car for spark, keep a backup battery source connected to avoid draining the main car battery. 

How to test for spark

Checking if you are getting an ignition spark with a test light is quite simple. Simply plug the spark plug inline tester between the spark plug and the ignition coil. 

Remove engine cover

If you have a vehicle model year 2000 and newer it will most likely have an engine cover. Remove the cover by lifting it up. Engine covers are simply held in place with tabs. 

diy guide on how to check is spark plugs are firing

Locate the spark plugs

On a four-cylinder engine, the spark plugs will be right on top of the engine. This is typically true for inline six engines as well. If your car is a V6 then you will have three cylinders on one side of the engine block and the other three on the other side.

how do you check for spark on a car

 

 

 

Disconnect the injector 

We don't want to flood the engine with fuel. Therefore as a best practice, it is recommended to unplug the electrical connector from the fuel injectors or remove the relay for the fuel pump.

If you are going to check only one of the cylinders for a spark for a couple of seconds, you may be fine without disconnecting the spark plugs. If you crank the engine for an extended period of time with the injector connected you will flood the cylinders with gasoline which can foul the spark plugs. 

check if spark plugs are firing in gasoline engine

Remove the ignition coil

Remove the ignition coil from the spark plug that you want to test. Unplug the ignition coil from the spark plug but keep it connected to the wire harness.

how to check engine for spark

 

Connect spark plug tester

Connect the inline spark plug tester in between the ignition coil and the spark plug. One end of the spark plug testers fit on the ignition coil and the other on top of the spark plug. 

how to check spark using test light

 

 

Check for spark

Set the spark plug tester aside. Now it is time to check if your engine is getting a spark. Keep your hands away from the ignition coil and the spark tester. Have a helper turn on the ignition and try to start the engine. 

As the engine turns over, look if there is a spark on the test light. If there is a small light flashing, it means you are getting a spark. If your car doesn't start, it is possible that you have a fuel related issue, timing issue. Also, check for bad spark plugs. 

If there is no light at all at the test light, you are not getting a spark. 

How to check for spark with a screwdriver

High voltage. Risk of injury. This method is not recommended.  

A quick and dirty method of checking for spark is using a screwdriver. 

Locate spark plug

You will need to pop the hood open. Remove that large engine cover and find the spark plugs. 

Remove spark plug wire or ignition coil

If you have a newer car you will most lily have an ignition coil on top of each of the spark plugs. Remove one of the ignition coils. If you have plug wires, remove one wire from the spark plug. 

Connect screwdriver to test for spark

Stick your screwdriver into the ignition coil or the plug wire boot. 

Place screwdriver near engine block

Place the screwdriver about 1/8" from the engine block. While someone else cranks the engine you should closely look at the gap between the engine and the screwdriver. If your ignition system is working properly you should see a spark here.

If your spark plugs aren't firing, then you won't see a spark here. Which means you have an ignition problem you need to address.  

Test for spark with no tools

Another method to check if you are getting spart at the spark plugs is to remove the spark plug from the engine.

how to check spark by removing the spark plugs

 

Plug it back on your ignition coil or spark plug wire and ground the threaded part of the spark plug to the engine block. 

how to check engine for spark

 

Make sure you unplug the injector or remove the fuel pump relay. As you crank the engine, you should see a small spark at the tip of the spark plug. 

There are several other ways to check a car engine if it is getting a spark. You can check for spark using a multimeter, test light, screwdriver or even by removing the spark plug and grounding it on the engine block or frame.

What to do if your car won't start

engine cranks but it will not start and you have already verified that the engine is getting a spark the problem could be any of the following: 

  • No fuel or low fuel pressure
    If your engine is not getting fuel, your car engine will not start. Check for fuel pressure. Check fuel pump operation. 
  • Ignition Module Defective
    If your vehicle is equipped with an ignition module it is possible that it can be bad. 
  • Bad Crankshaft Position Sensor (CPS)
    On newer vehicles, the crankshaft position sensor plays a key role in determining the position of the crankshaft. If it fails you will notice intermittent starting issues. Typical symptoms include car starts fine when cold but when it warms up. The problem with CPS sensor is that it may not even trigger the check engine light on in some cases. 
  • Timing Issue
    If there is a timing issue and valves don't close when the pistons hit Top Dead Center (TDC), your car won't start. 
  • Low compression
    Low cylinder compression can also cause no start conditions. 

If you are getting spark at all ignition coils except one of them, the most lily cause is a bad ignition coil or a cut wire for that particular ignition coil.

Conclusion

The methods described here helps you learn how to check for ignition spark. If your car doesn't start it is important to look at other possible issues such as fuel pressure. This guide only shows you how to check if the spark plugs are firing nothing more.  

While these instructions were meant to help learn how to check for spark on a car engine, these methods can be used to check for spark on lawn mower and motorcycles as well or any large or small gasoline engine. 

FAQ

How to check if a spark plug is firing without a test light?

An alternative method to check if a spark plug is firing is to remove the spark plug from the engine. Plug the spark plug on your ignition coil. Ground the threaded part of the spark plug to the engine block. Crank the engine and see if you are noticing any spark at the spark plug tip. 

 

How do I know if I need new spark plugs wires?
  • Most owners realize they need new spark plug wires when their car starts to miss fire, struggle to accelerate uphill or sets the check engine light with codes such as P0300 P0301 P0302 P0303 P0304 P0304 P0304. 
  • There are ways to tell if you need new spark plug wires. Use an insulated screwdriver and move it along the spark plug wires (at least two wires). Do you notice any arc from the wire to the screwdriver? If you do, it means you need new spark plug wires.