How to test injectors using a Noid Light

How to test injectors using a Noid Light is easier than you think.

A fuel injector Noid light kit should be on your must have tool list.

Noid Lights come in many different types and are relatively inexpensive. Get a good one that comes with all the attachments you need for any vehicle. These kits contains Noid lights for the different fuel injector connectors used on the majority of makes and models. Not all cars use the same fuel injector connector type.

noid light
noid light

A fuel injector Noid light will help you to troubleshoot a misfire, No Start  or a BAD fuel injector. It is one of those MUST HAVE tools to diagnose the majority of fuel injected vehicles on the road today.

This test will tell you if the computer is pulsing the fuel injectors open when cranking the engine over. Most of the time this test is done when the engine is cranking over but not starting.  However, you can do this test when the engine is running. You will be able to see if a certain fuel injector is getting a signal to fire.

All fuel injectors need power and a switching signal from the fuel injection computer. This little tool helps you to visually confirm that the fuel injector is getting both. Now, a fuel injector Noid light test won’t tell you that the fuel injector is BAD, but will confirm that it is getting power and the Switching signal (also known as the fuel injector pulse signal).

Without any of these two signals, the fuel injector will not work.As mentioned before, every make (Ford, Chevrolet, Nissan, etc.) will have a different type of fuel injector connector. So you’ll have to choose the fuel injector Noid light that will easily fit into the fuel injector connector to be tested.

Here are the test steps:

1>  Locate the fuel injector that you’re gonna’ test and disconnect it from its electrical connector. The fuel injector may have a metal clip securing the connector to the fuel injector, which you’ll need to press in order to unlock the connector to remove it. The connector will have a plastic locking tab integrated into it that needs to be pressed as you gently pull back on the connector.

2>  Some fuel injector connectors don’t have a pressable metal clip. With this type of connector, you’ll need to remove this metal clip from the fuel injector connector first.

3>  Once the fuel injector connector is removed, insert the fuel injector Noid light into it. The Noid light should fit into the connector as easily as the fuel injector it mates to. Do not force the Noid light into the fuel injector connector if you encounter resistance from it, instead, choose another Noid light from the kit that will easily slip into the fuel injector connector.

4>  When ready and a safe distance from the engine, where you can easily observe the Noid light, have a helper crank the engine. If all is well, the Noid light will flash on and off the whole time the engine was cranking. If the engine started, the Noid light should flash on and off the whole time the engine was running.

5>  Now, if the Noid light did flash on and off, it’s always a good idea to test the fuel injector connector next to the one you just tested and compare both results. If all is good, both connectors should make the Noid light flash in the exact same way.

Interpreting the Results of the Noid Light Test

If the Noid light flashed on and off and this flashing was comparable to the fuel injector connector next to it, then this result indicates the the fuel injector is getting power (usually in the form of 10 to 12 Volts) and that the fuel injection computer is providing a fuel injector pulse signal to activate it. Also, this test result eliminates the electrical end of the fuel injector circuit as the cause of the problem or misfire.

If the Noid light DID NOT flash on and off, this result indicates the the fuel injector is either NOT getting power (usually in the form of 10 to 12 Volts) or that the fuel injection computer is NOT providing a fuel injector pulse signal to activate it. With this result, you have confirmed that the electrical part of the fuel injector circuit is at fault.

Noid Light kit
Noid Light kit


Here are some quick tips on how to use Noid lights.

1>  If the Noid light stays on with the key on or when cranking, chances are wiring on the ground side of the circuit is either shorted out (shorted to ground) or the driver inside the computer is bad and the computer may need to be replaced.

2>  If the Noid light does not blink at all when cranking the engine over, check for fuel injector pulse at multiple cylinders as you may just have an issue with that specific circuit.

3>  If there is no pulse on all cylinders, check to see if the fuel injector is getting power with the key on and cranking.  If still no injector pulse, then the computer is not pulsing the injectors open for some reason and more testing will be needed.

4>  Again, you want the Noid light to blink consistently when cranking the engine over.  This is a good signal.So there you have it , Problem Solved !! or Now you know where to look next.

About Danny Bender 104 Articles
DannysEnginePortal.com Is The Premier Automotive Engine Troubleshooting Resource Site. DannysEnginePortal.com Shares Information On Engine Troubleshooting, Engine Rebuilding, Engine Repair Tips, Tech Info, Basic Machining, Automotive Testing, In addition To Possible Solutions.

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