How To Test The Fuel Injectors (2011-2019 1.6L Ford Fiesta)

How To Test The Fuel Injectors (2004, 2005 2.0L SOHC Neon)

Testing the fuel injectors on your Ford Fiesta is a piece of cake since they're very accessible (no need to remove a ton of stuff like on other vehicle).

In this tutorial, I'm going to explain how to test their internal resistance to see if they have suffered an internal short-circuit or open-circuit problem (which would cause them to stop spraying any fuel).

This is a super easy test that you can do with a multimeter. All of the test steps are explained in detail.

APPLIES TO: This tutorial applies to the following vehicles:

  • 1.6L Ford Fiesta: 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018.

Symptoms Of A Bad Fuel Injector

It's been my experience over the years diagnosing engine performance problems, that fuel injectors usually fail in one of two ways:

  • The fuel injector stops injecting fuel completely.
  • The fuel injector becomes clogged.

The second issue (fuel injector becoming clogged) is the one I've encountered the most. In these cases, even tho the fuel injector is spraying fuel, the way in which it does prevents the fuel from getting atomized correctly. Both types of issues lead to a misfiring cylinder.

These are the most common symptoms you'll see when one fails:

  • Rough idle.
  • Lack of power.
  • The engine hesitates when you accelerate under load.
  • Cylinder misfire trouble codes:
    • P0300: Random Cylinder Misfire.
    • P0301: Misfire In Cylinder #1.
    • P0302: Misfire In Cylinder #2.
    • P0303: Misfire In Cylinder #3.
    • P0304: Misfire In Cylinder #4.

Whether the injector has an internal electrical issue or is clogged, this tutorial has got you covered with the info you need to find out exactly what's going on. No more throwing money at guesses, you'll know exactly what's wrong. If the injector resistance test doesn't identify the issue, this section will:

Checking The Resistance Of The Fuel Injectors

Checking The Resistance Of The Fuel Injectors With A Multimeter. How To Test The Fuel Injectors (2004, 2005 2.0L SOHC Neon)

To find out if the injector has suffered an internal electrical problem, we're gonna check the internal resistance of all four fuel injectors with a multimeter set to Ohms mode.

What we're looking for is for a fuel injector who's resistance isn't similar to the others. Typically, if the fuel injector has suffered an internal circuit problem, you'll see:

  • The fuel injector's resistance is 1 Ohm or less (indicating a short-circuit problem).
  • The fuel injector's resistance will be in the K (thousands) Ohm range (indicating an open-circuit problem).
  • The fuel injector's resistance will be higher or lower by 10 or more Ohms.

NOTE: Although this test is done with the engine off, test the fuel injectors with a warmed up engine to get the most accurate test result.

Let's get started:

  1. 1

    Disconnect the fuel injectors from their electrical connectors.

    NOTE: This test is done with the engine OFF.

  2. 2

    Set the multimeter to Ohms (Ω) mode.

  3. 3

    Measure the fuel injector's resistance across its two male terminals with the multimeter probes (see the illustration above).

  4. 4

    Record the resistance value that your multimeter shows for the specific fuel injector you're testing.

    NOTE: Cylinder #1 is the one closest to the drive belt. Cylinder #4 is the one closest to the transmission.

  5. 5

    Repeat steps 1 to 3 for the remaining fuel injectors.

Let's interpret your test results:

CASE 1: The resistance of each injector is similar. This is the correct test result and confirms that none have an internal short-circuit or open-circuit issue.

If you suspect a clogged fuel injector (something the resistance test can't detect), go to: How To Find The Bad Or Clogged Fuel Injector.

CASE 2: One of the fuel injectors recorded a resistance value that is much higher or lower (10 Ohms or more). This tells you that the fuel injector is bad. Replace the fuel injector.

How To Find The Bad Or Clogged Fuel Injector

Finding the clogged fuel injector isn't that much more difficult. In this test section, I'll explain my method for finding the fuel injector that's clogged and causing a misfire or a rough idle problem.

To find the clogged (or bad) fuel injector on your Ford Fiesta, requires doing a set of tests. Each test is designed to eliminate a possible issue as the source of the misfire.

These are the steps of my testing strategy:

  1. First, find the 'dead' cylinder.
    • This is the most important first step. You can do this by connecting an automotive scan tool (or code reader) and reading the fault codes stored in your Neon's fuel injection computer's memory.
    • You can also perform a manual cylinder balance test (my go-to method to find the 'dead' cylinder):
  2. After identifying the 'dead' cylinder, make sure it's receiving spark.
    • This simply involves connecting a spark tester to the 'dead' cylinder's spark plug wire and cranking the engine. If the spark tester sparks, they 'dead' cylinder is getting spark.
    • You also need to check that the 'dead' cylinder's spark plug boot and the spark plug are NOT soaked (or swimming) in engine oil.
    • You should also remove the spark plugs and check for cracks or carbon tracks (this is VERY important).
  3. If the 'dead' cylinder is getting spark, the next step is to make sure it has good compression.
  4. If the 'dead' cylinder has spark and good compression, the next step is to test the fuel injector's activation signal with a Noid light.
    • If every test gives you the correct and expected result, the next step is to make sure the fuel injector is receiving its activation signal.
    • The following tutorial on how to use a Noid light explains how to check for the fuel injector activation signal: (I know this isn't the most detailed article on the topic, but it should give you an idea of what's involved).
  5. If the 'dead' cylinder has spark, good compression, and the fuel injector is being activated; the next step is to swap the fuel injector.
    • If I find that I have a specific 'dead' cylinder and:
      1. The ignition system isn't behind the issue.
      2. The compression value of that cylinder is fine (compared to the rest of the cylinders).
      3. The fuel injector's resistance is fine and it's being activated by the fuel injection computer...
      4. I think the fuel injector is clogged, I then swap that fuel injector with an adjacent one.
      If the cylinder failure now follows that swap, I now know that the fuel injector is clogged (or faulty) and needs to be cleaned or replaced.

The list of tests might look long and intimidating, but it's actually simple and doable. You can do them all with simple and affordable tools.

The key takeaway of this testing strategy is that it's a step-by-step elimination process. You check one component, and if it's good, you move on to the next. It's the exact approach a tech at the shop takes, and now you can do it yourself.

More 1.6L Ford Fiesta Test Tutorials

If this tutorial was helpful, be sure and take a look at all of the 1.6L Ford Fiesta diagnostic tutorials in this index:

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

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