How To Test The Fuel Injectors (1998 4.6L Crown Victoria, Grand Marquis)

How To Test A Bad Fuel Injector (1998 4.6L Ford Crown Victoria And 4.6L Mercury Grand Marquis)

Like most of the components on your car, the fuel injectors can be tested to find out if they are bad or not.

In other words, you don't have to run out to your local auto parts store to buy one not really knowing if it has failed or not. In this tutorial, I'm gonna explain the multimeter resistance test you need to know to test them all.

Also, finding the bad or clogged fuel injector is not that hard. In the next page I'm gonna show you a very simple troubleshooting method to find the clogged (or failed) fuel injector.

APPLIES TO: This tutorial applies to the following vehicles:

  • 4.6L Ford Crown Victoria: 1998.
  • 4.6L Mercury Grand Marquis: 1998.

Wiring Diagram: The following fuel injector circuit wiring diagram is available to further help you:

NOTE: The following tutorials may be of help to test the fuel injectors on the Crown Victoria (Mercury Grand Marquis) not covered by this tutorial:

Symptoms Of A Bad Fuel Injector

Because every cylinder on your 4.6L V8 engine needs fuel, air, and spark to produce power, when the fuel injector stops working (or doesn't spray enough fuel because it has become clogged) the engine in your car is going to suffer a misfire.

Here are a few other symptoms you'll see:

  • Rough idle.
  • Lack of power.
  • Hesitation when you accelerate your car down the road.
  • Misfire trouble codes:
    • P0300: Random Cylinder Misfire.
    • P0301: Cylinder #1 Misfire.
    • P0302: Cylinder #2 Misfire.
    • P0303: Cylinder #3 Misfire.
    • P0304: Cylinder #4 Misfire.
    • P0305: Cylinder #5 Misfire.
    • P0306: Cylinder #6 Misfire.
    • P0307: Cylinder #7 Misfire.
    • P0308: Cylinder #8 Misfire.

Where To Buy The Fuel Injector And Save

If your test results indicate that you've got a bad fuel injector on your hands, then check out the following. I think that they will help you to comparison shop for a fuel injector and save a couple bucks in the process.

Not sure if the above fuel injectors fit your particular 1998 4.6L Ford Crown Victoria? Don't worry, once you click on the links and arrive on the site, they'll make sure it fits! If it doesn't, they'll find you the right one.

What Tools Do I Need To Test The Fuel Injectors?

To perform a fuel injector resistance test, you don't need a lot of stuff. Here's a basic list of tools you'll need:

  1. A multimeter.
  2. Hand-held DIY fuel injector cleaning tool kit.
    • This tool allows you to pulse (activate) the fuel injector while connected to a spray can of brake cleaner, making it super easy to visually check the injector's spray pattern and see if it's clogged.
    • You can learn more about this tool and where to buy it in this section: PART 2: Checking The Fuel Injector Spray Pattern.
  3. OBD II scan tool or code reader.
    • 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.
  4. Hand Tools.
    • You'll need hand tools like: socket wrench, extensions, sockets, etc. to remove the fuel injector to test its spray pattern.
  5. Pen and Paper to write down your fuel injector resistance test results.

The Strategy: How To Find The Bad Or Clogged Fuel Injector

One of the most important things to remember, is that whether the fuel injector has an internal open or short-circuit problem or is just clogged, it'll cause a misfire. This misfire will lead to a misfire trouble code that will light up your Crown Victoria's check engine light.

This also means that the same troubleshooting process can be applied to finding either a failed or clogged fuel injector. How do I know? From the results of my personal experience as an automotive technician.

I can also tell you that finding the bad or clogged fuel injector is not hard because most of the components that need to be tested (in order to be eliminated as a source of the misfire) on your 4.6L Crown Victoria are very easy to get to and in plain view.

OK, this is my troubleshooting method:

  1. Find the 'dead' cylinder first.
    • By dead cylinder, I mean the misfiring cylinder. This is the most important first step and can not be overlooked. You can do this by connecting a scan tool (or code reader) and identifying the specific misfire code that's registered in your car's PCM memory.
  2. After identifying the 'dead' cylinder, make sure it's getting spark.
    • It's important that you check the tower (of the ignition coil pack assembly) for spark with a dedicated spark tester.
    • It's important that you check that the spark plug boot and spark plug are NOT soaked (or swimming) in engine oil.
    • You should also remove the spark plugs and check them for cracks or carbon tracks (this is SO important).
  3. If the 'dead' cylinder has 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 a fuel injector Noid light test.
    • If every test above checks out OK, then the next step is to make sure that the fuel injector is being activated.
    • The following Noid light article/tutorial may help you: How To Use A Noid Light And Where To Buy It (at:

      NOTE: 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. If the 'dead' cylinder has spark, good compression, and is being activated; the next step is to check the fuel injector.
    • The first thing to do is to check the fuel injector's internal resistance.
    • The second part of the test involves using brake cleaner spray with a special adapter tool to visually check whether the fuel injector is indeed spraying fuel.
    • In lieu of the fuel injector spray test, you can swap out that fuel injector with its neighbor. If the misfire now follows that swap, the fuel injector is clogged (or bad) and needs to be cleaned or replaced.

As you can see, finding the cause of the misfire boils down to a process of elimination. As you start off by identifying the 'dead' cylinder, the next steps are too make sure that it's getting spark, good compression, etc.

PART 1: Checking The Injector's Internal Resistance

How To Test A Bad Fuel Injector (1998 4.6L Ford Crown Victoria And 4.6L Mercury Grand Marquis)

I'm gonna suggest that you test all 8 fuel injectors on your 1998 4.6L Crown Victoria (1998 4.6L Grand Marquis). Yep, even if you have a specific misfire trouble code, I recommend that you test them all.

IMPORTANT: The fuel injector resistance specification is 11 - 18 Ohms.

Now of course you're going to need a multimeter to be able to test the resistance value of the fuel injectors, if you don't have one and are looking to buy a multimeter, check out my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing (at:

Alright, lets get testing:

  1. 1

    Disconnect the fuel injectors from their engine wiring harness connectors.

    NOTE: The illustration above will help you to identify the number of each cylinder so that you'll know which fuel injector belongs to what cylinder.

  2. 2

    Set your multimeter to Ohms (Ω) mode.

  3. 3

    Measure the resistance of the fuel injector across its two male spade terminals with the multimeter test leads (see the illustration above).

  4. 4

    Write down the resistance value that your multimeter records for the specific fuel injector you're testing.

    The illustration above will help you identify the cylinder # the fuel injector belongs to.

  5. 5

    Repeat steps 1 through 4 on the remaining fuel injectors.

    NOTE: The fuel injector resistance specification is: 11 to 18 Ohms.

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

CASE 1: Your test results indicate that all 8 fuel injector resistances are within specification (11 to 18 Ohms). This tells you that the internal coil winding of each fuel injector is OK.

But, there's a chance that the misfiring cylinder has a clogged fuel injector. So my suggestion is to check out the troubleshooting guidelines in this section: PART 2: Checking The Fuel Injector Spray Pattern.

CASE 2: Your test results indicate that one or several fuel injectors ARE NOT within specification. If the fuel injector's resistance value is not within the 11 - 18 Ohms specification, you can conclude that that fuel injector is fried and needs to be replaced.