How To Test A Fuel Injector (Chrysler 2.0L, 2.4L)

A fuel injector resistance test can easily determine if a fuel injector on your Dodge Neon (or Stratus or PT Cruiser or Cirrus or Breeze, etc) is defective or not. This test doesn't require that you use expensive testing equipment, since a simple multimeter will suffice.

A bad fuel injector will cause your Neon (or any 2.0L (SOHC, DOHC), 2.4L (DOHC) equipped Chrysler vehicle) to idle rough, run rough, and light up the check engine light with either misfire codes (P0300, P0301, P0303, P0304) or fuel injector diagnostic trouble codes (P0201, P0202, P0203, P0204).

You can find this tutorial in Spanish here: Cómo Probar Los Inyectores De Combustible (Chrysler 2.0L, 2.4L) (at: autotecnico-online.com).

CYLINDER MISFIRE DIAGNOSTICS:

• How To Test Misfire Codes (Chrysler 2.0L, 2.4L).

Symptoms Of A Bad Fuel Injector

The most common and obvious symptom of a bad fuel injector will be that your car's engine will have a rough idle and an engine miss when you accelerate it down the road.

What really stinks is that the PCM won't always set a specific fuel injector trouble code. But if it does, you'll see one of the following:

• P0201: Injector #1 Control Circuit.
• P0202: Injector #2 Control Circuit.
• P0203: Injector #3 Control Circuit.
• P0204: Injector #4 Control Circuit.

From personal experience over the years, what's really interesting is that around 90% of the time, when you do have a bad fuel injector, you'll see a misfire trouble code:

• P0301: Cylinder #1 Misfire.
• P0302: Cylinder #2 Misfire.
• P0303: Cylinder #3 Misfire.
• P0304: Cylinder #4 Misfire.

And well the other symptoms your vehicle may experience are:

• Lack of power.
• Bad gas mileage.
• Check engine light is on.

What Tools Do I Need To Test The Fuel Injectors?

To test the fuel injectors in your Chrysler 2.0L or 2.4L equipped car you don't need any expensive tools.

Here's a basic list of tools you'll need:

1. A multimeter.
   • You'll only be using the multimeter to check resistance (Ohms).
   • If you need to upgrade or buy a multimeter, this is the one I use and recommend: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link).
2. Scan tool.
   • To actually test the fuel injectors, you don't need a scan tool (since a scan tool can't dynamically test the fuel injectors). But, having one makes the whole process easier since you're able to retrieve any diagnostic trouble codes (DTCs) stored in the PCM memory.
   • Don't have one? Check out my recommendation: ZM301 OBD2 Scanner Diagnostic Tool (Amazon affiliate link).
3. Pen and paper to write down your fuel injector resistance test results.

The Fuel Injector Test

The best way to run this test is with the engine in your Stratus (or Cirrus, PT Cruiser, Voyager, etc.) slightly warmed up. If the engine's been running and is hot, let it cool for about an hour. If it's stone cold, crank it up and let it warm up for about 10 minutes.

Warming the engine first gives you a clearer picture of the injectors' condition, but it's not absolutely necessary.

The reason I point this out is because sometimes the injectors are already off the car, or maybe the car won't start at all. In those cases, you don't need to reinstall them or run the engine just to warm it up —you can test them cold.

Also, you don't have to test every single injector if you don't need to. This is especially true if you have a repair manual for your Chrysler 2.0 (SOHC/DOHC) or 2.4L (DOHC) with the resistance spec listed.

The main reason I recommend testing them all is to save you from hunting down the spec online or in a book. By checking every injector, you'll see the average Ohms value across the set, which gives you a reliable baseline —even if you don't have the spec handy. Of course, the more information you've got, the better, but this way you're not stuck looking it up.

Some vehicles (like the PT Cruiser) require that the intake manifold's plenum be removed to gain access to the fuel injectors. If this is the case in your particular 2.4L (DOHC) vehicle, please read this section: Safety Tips For Removing The Intake Manifold Plenum.

Alright, here are the steps:

1. 1

   Unplug all four fuel injectors from their electrical connectors.

2. 2

   Grab your multimeter and place it in Ohms mode.

3. 3

   Probe the fuel injectors two male spade terminals with the multimeter test leads.
   
   In case you're wondering, it doesn't matter which test lead (black or red) you use on which terminal on the fuel injector, since the polarity doesn't matter in a simple resistance test.

4. 4

   Write down the Ohms (resistance) value that your multimeter is registering on a piece of paper.
   
   Write down what engine cylinder that fuel injector belongs to, too.

5. 5

   The fuel injector resistance value will be around 11-18 Ohms.
   
   On your particular 2.0L (SOHC, DOHC) or 2.4L (DOHC), the actual value your multimeter registers might be a different. Don't fret over this and you'll see why when you interpret the resistance value of all four.

6. 6

   Repeat the above steps on the remaining fuel injectors..

Let's find out what your specific multimeter test results mean:

CASE 1: All four fuel injectors registered the same resistance values. This confirms that the fuel injector your are testing is OK internally (no short or open circuit problem).

Here's why: If any one of the fuel injectors were bad, your multimeter would've registered a completely different resistance value for that fuel injector. Since your resistance (Ohms) value were the same for all then this is an indication that the fuel injectors do not have an internal electrical fault.

CASE 2: One of the four fuel injectors registered a completely different resistance value. This indicates that the fuel injector is bad. Replace the fuel injector.

Fuel Injector Diagnostic Strategy

Finding the bad fuel injector is not hard to do if you have a specific diagnostic strategy. In this section, I'm gonna' share with you the way I diagnose a bad fuel injector (and of course, you can modify my testing suggestion to fit your specific needs).

I first start by:

1. Check for misfire trouble codes.
   • This is the most important first step -identifying the "dead" (misfiring) cylinder.
   • You won't always have a specific bad fuel injector code, but you'll definitely have a misfire code (around 90% of the time that is).
2. Check the ignition system for spark.
   • Before I even start thinking that I may have a bad fuel injector, I make sure that every engine cylinder is getting spark.
   • I check that each spark plug wire is feeding spark to the spark plug.
   • I check that the spark plug wire boot and spark plug are NOT soaked (or swimming) in engine oil.
   • I remove the spark plugs and check them for cracks or carbon tracks (this is SO important).
     • Here's a real life case study on carbon tracks and how they can cause a misfire: Carbon Tracks Are A Common Cause Of Ignition Misfires (at: easyautodiagnostics.com).
   • You can find an in-depth step-by-step tutorial on how to test the ignition system here: How To Test The Ignition Coil Pack (Chrysler 2.0L, 2.4L) (this info is found at: easyautodiagnostics.com).
3. Check engine compression.
   • After making sure that the ignition system and all its components are OK, I check for low engine compression.
   • This is one of the most overlooked tests when diagnosing a misfire or rough idle condition.
   • You can find the test here: How To Test The Engine Compression (Chrysler 2.0L, 2.4L).
4. Noid Light Test.
   • If every test above checks out OK, I do a fuel injector Noid light test.
   • The Noid light test will help you make sure that the fuel injector is getting activated.
   • The following Noid light article/tutorial may help you: How To Use A Noid Light And Where To Buy It (at: easyautodiagnostics.com) -I know that this is not the most in-depth article on the subject, but it should give you an idea of what is involved.
5. Swap the fuel injector with its neighbor on the fuel injector rail.
   • If I've found out that I have a specific 'dead' cylinder, I'll swap out the fuel injector if:
     • The ignition system is not at fault.
     • The cylinder's compression value is good (compared to the rest of the cylinders).
     • The fuel injector resistance is good.
     • I think the fuel injector is clogged.
   • If the misfire now follows that swap, I now know that fuel injector is clogged (or bad) and needs to be cleaned or replaced.

The above testing strategy may seem like overkill or too difficult but it isn't. Most of the above tests can be done pretty fast and are not hard to do.

I can tell you from experience that the way to save yourself the frustration of replacing good parts, your vehicle doesn't need and that don't solve the problem, is testing everything. Thankfully, there's a test for just about anything on your car!

Safety Tips For Removing The Intake Manifold Plenum

As mentioned earlier, some vehicles have the fuel injectors under the intake manifold plenum and this plenum has to be removed to test the fuel injectors underneath.

One thing that I have done whenever it's been possible, is to use a fuel injector connector that I have cut from an old Chrysler wiring harness. And with a little patience and perseverance, I have disconnected the fuel injector's connector (the one that I'm going to test and that is underneath the plenum) and installed the one I cut from the old wiring harness, and performed the test described in this article by testing the ends of the cut connector (and without having to remove the plenum).

On some, I have just removed the plenum and followed the following tips:

1. Keep hardware out of the engine bay: As I'm removing bolts, nuts, etc., I'm placing them in a container and away from the engine. This is important since I want to avoid having anything fall into the open intake manifold runners that are now exposed with the plenum removed.
2. Cover the intake runners: I have clean rags at the ready, and when the plenum is finally off, I immediately cover the four open intake runners with them. In other words, I stuff those rags into the open intake runners. This will help to keep any foreign object from falling into them.
3. Always use new gaskets: I use new gaskets. I do not re-use the old intake manifold plenum gasket, and neither should you. Also, when installing the new ones, do not coat them in any type of sealer (like RTV silicone). This is not necessary and could backfire on you since the sealer can cause a vacuum leak.

If anything falls into an open intake manifold runner, without you knowing it, you're going to be in a world of hurt because once you put everything back together and you start the engine, it's gonna' knock! The only way to remove whatever fell in there, is to remove the engine's cylinder head.

I have removed the intake manifold plenum on these 2.4L (DOHC) many times and without complications. You can too, if you keep in mind the above suggestions.

More Diagnostic Tutorials

If this article confirmed that the fuel injectors are good and not the cause of the rough idle condition or misfire condition, and yet your car (or mini-van) is still running rough, I suggest testing the ignition system. Below are the links to two 2.0L (SOHC, DOHC) and 2.4L (DOHC) ignition system test articles (they are found at easyautodiagnostics. Com):

• How To TEST 2.0L And 2.4L Coil Packs Chrysler, Dodge, Eagle, Plymouth And Mitsubishi (at: easyautodiagnostics.com).
  • How to test the ignition coil pack, spark plug wires, and ignition coil pack signals on all 2.0 (SOHC, DOHC) and 2.4L (DOHC) Chrysler, Dodge, Plymouth, Eagle and Mitsubishi vehicles.
• Carbon Tracks Are A Common Cause Of Ignition Misfire! (at: easyautodiagnostics.com).
  • This is a real life case study on how to diagnose a misfire condition due to a carbon track on the spark plug wire boot.

Here, at troubleshootmyvehicle. Com, you can find all of the 2.0L and 2.4L Chrysler Test Articles by clicking here: Chrysler 2.0L, 2.4L Index Of Articles.

Here's a sample of the tutorials you'll find in the index:

• How To Test The Engine Compression (Chrysler 2.0L, 2.4L).
• How To Test The Engine Compression (Chrysler 2.0L, 2.4L).
• How To Test The Crank Sensor (Chrysler 2.0L, 2.4L).
• How To Test Misfire Codes (Chrysler 2.0L, 2.4L).