Engine Problems – How to Test 6.7 Cummins Injectors

Searching for the best process on how to test 6.7 Cummin Injectors? Then, you will find that here in this writing.

A fuel injector is a part of the vehicle’s engine. It helps to create pressure on the fuel and consequently provides energy to the engine to run smoothly.

But after thousands of mile driving, the fuel injector of the engine can be damaged or have issues. And it impacts on the engine start. Then, we feel the necessity of checking injectors as there is more than one injector in an engine.

To find the faulty one, we need to test all. In this writing, you will know about the process that is not only for 5.9 -6.7 Cummins but also for other engines.

What is Injectors?

Before knowing about the testing process, let’s have some ideas on fuel injectors and where you will find it.

Well, fuel injectors look kind of a syringe from outside. But inside, it works like a valve. The does up and down several times within a second. And for that, it creates pressures in the fuel to provide energy to the engine.

Generally, an injector has three-part inside it-solenoid, spring, coil, and pin. When the spring coil gets a charge from the battery, it creates an electric magnetic field, and it pulls the pin-up and spreads fuel to the engine with high pressure.

Again, when the coil got out of the charge, the pin comes down, and the same process repeats. This cycle continues and can do up-down several times in a second.

Most of the car has more than two injectors. All the nozzles-like injectors are kept together connected through an injector trail line pipe. You can find them under the front hood, mostly beside the battery.

Why Need to Test Fuel Injectors

Now, if you have understood about the injector’s working function, then you should know about the injector failure symptoms. It would help if you were sure of the fact that it is your injector that got some issues.

Otherwise, it may be a waste of time to test the injectors, whereas the problem maybe some other.

Symptoms of a bad fuel injectors

  •  The car takes a hard start
  • Vehicle making a terrible noise and shaking
  • The car does not run smoothly
  • Code reader showing error codes from P0300 to P0308
  • Dashboard showing signals of ignition error

If you face any of these signs, then it’s sure that the problem is in the injector. You need to check the injector and find out the faulty one.

The injector may get damaged because of increasing resistance inside it for bad fuel or not having proper fuels.

How to Test 6.7 Cummins Injectors

We will be showing you two easy and simple process of testing injectors.

Process 1:  Hearing  Injector Sounds

It is the most common process. It is also straightforward and does not need too many equipment to test.

Step 1: Open the Front Hood of the Engine

Open the front hood of the engine and find out the injector rails. As we have mentioned, the injector rail is the long pipe connecting all the injectors.

Step 2: Take a Long Rod

Now, take any long rod type metal. The rod should be fully metallic.

Step 3: Put the Screw on the injector & Hear Sounds

Now, put one end of the rod on one injector and try to hear from the other side of the rod. If you hear some injection triggering sound, then that injector is okay and working well.

Repeat doing this on other injectors also. If you find anyone not making a sound, then that one is your faulty injector. You have to replace that.

Process 2:  Using a Multimeter

You can also check the injectors by using a multimeter. For this, you just need a multimeter. And thinking about cables to connect? Then don’t worry, you will get the connecting wires with the meter.

You don’t need any high branded multimeter. Any good condition multimeter that can detect and measure electric activities will be enough to test the injectors.

Step 1: Set the Meter

We will be testing the resistance with the meter.  Turn the switch on and set towards the Ohm sign that is also like an omega sign.

If you don’t know bout Ohm sign then, you will see there is written Ohm, Amp like this. You need to twist the switch toward Ohm.

Step 2: Connect the Cables

Now connect the cables. The black wire will go into the com signed port of the multimeter, and the red wire will go on Ohm signed port.

On the other hand, open anyone cap of the injector, and you will see two raising plugs. Connect the wires from the multimeters with these two plugs. It does not matter which color you connect to what.

Step 3: Check the Resistance Reading

Now, the multimeter will automatically start giving the reading. See how many resistance it shows.

Repeat step-2, step-3 for every injector, and check the reading of the resistance.

If your car manual tells you a resistance range of the injectors, then check if any injectors have more resistance than the given range or not. If it is more than the range like 10 Ohm, 16 Ohm, etc. then be sure that one is your culprit injector.

After applying any one of the methods above, if you still don’t find your injector faulty, then the problem might be in your ignition system or the fuel lines.  Check your fuel line pipe and engine’s battery providing proper power.


In this writing, we have shown two simple but effective methods on how to test 6.7 Cummins injectors, and you can apply these methods for other engines also.

Don’t delay, and don’t drive your vehicle with any faulty signs. Driving a car after getting fault signs is like committing suicide!

So, read this now and know about the methods to test by yourself.