How To Test The Fuel Injectors (1992-1997 4.6L Crown Victoria, Grand Marquis)

What makes testing the fuel injectors on the 4.6L V8 Crown Vic or Grand Marquis easy, is the fact that they're very easy to get to (on other fuel-injected V8 engines you have to do quite a bit of a tear down to get to them).

In this tutorial, I'm going to explain how to test each one with a simple multimeter resistance test. This test will tell us if the fuel injectors internal coil winding has shorted or not.

APPLIES TO: This tutorial applies to the following vehicles:

• 4.6L Ford Crown Victoria: 1992, 1993, 1994, 1995, 1996, 1997.
• 4.6L Mercury Grand Marquis: 1992, 1993, 1994, 1995, 1996, 1997.

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

• Fuel Injectors Circuit Wiring Diagram (1996, 1997 4.6L Crown Victoria, Grand Marquis).

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:

• How To Test The Fuel Injectors (1998 4.6L Crown Victoria).
• How To Test The Fuel Injectors (1999-2000 4.6L Crown Victoria).

Symptoms Of A Bad Fuel Injector

The fuel injectors on your van will typically encounter one of two main issues:

• Internal short-circuit or open-circuit: In this case, the injector's internal wiring has an electrical fault, stopping it from injecting fuel.
• Clogged fuel injector: Here, the injector can still inject fuel but fails to atomize it properly, meaning it doesn't spray the fuel in a fine mist. This lack of atomization causes the cylinder to misfire because the fuel can't combust properly.

The most obvious symptom that a failed or clogged fuel injector will cause is a misfire condition, but it's not the only symptom you'll see. Here are the most common symptoms you'll see when an one fails:

• Rough idle.
• Lack of power.
• Hesitation when you accelerate your car down the road.
• If your 4.6L Ford Crown Victoria is equipped with the OBD II system, you'll see one of the following fuel injector trouble codes:
  • P0201: Cylinder #1 Fuel Injector Control Circuit.
  • P0202: Cylinder #2 Fuel Injector Control Circuit.
  • P0203: Cylinder #3 Fuel Injector Control Circuit.
  • P0204: Cylinder #4 Fuel Injector Control Circuit.
  • P0205: Cylinder #5 Fuel Injector Control Circuit.
  • P0206: Cylinder #6 Fuel Injector Control Circuit.
  • P0207: Cylinder #7 Fuel Injector Control Circuit.
  • P0208: Cylinder #8 Fuel Injector Control Circuit.
• If your 4.6L Ford Crown Victoria is equipped with the OBD II system, you'll see one of the following 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

The following links will help you to comparison shop for a fuel injector:

Not sure if the above fuel injectors fit your particular 4.6L Ford Crown Victoria (4.6L Mercury Grand Marquis)? 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.
   • The multimeter will help you check the internal resistance (Ohms) of the fuel injector(s).
   • If you need to upgrade or buy a multimeter, check out my recommendation: Buying A Digital Multimeter For Automotive Diagnostic Testing.
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 and check 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

The really cool thing about the 4.6L Ford engine, is that all of the eight fuel injectors are easy to get to. This makes it super easy to find out which is the fuel injector that's bad.

Still, troubleshooting a bad/clogged fuel injector when you have a 8 of them can seem quite intimidating. So in this section I'm going to share with you my method of diagnosing a bad fuel injector. It's a very simple method that has helped me find the cause behind the misfiring cylinder (whether it's due to a bad fuel injector or something else).

OK, these are the steps I follow:

1. Find the 'dead' cylinder first.
   • Half the battle is won if you can find the 'dead' cylinder. In other words this is the most important troubleshooting first step. If your Crown Victoria (Grand Marquis) is OBD II equipped, then all you need to do is check for misfire trouble codes.
   • If your Crown Vic is not OBD II equipped, then you'll need to do a manual cylinder balance test to find it.
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.
     • Here's a tutorial that'll help you test the ignition coil packs on your 4.6L Ford Crown Vic: How To Test The 2 Coil Packs (Ford 4.6L V8).
   • 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).
     • 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).
3. If the 'dead' cylinder has spark, the next step is to make sure it has good compression.
   • After making sure that the 'dead' cylinder's plug wire is delivering spark, you need to 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 Engine Compression (1992-2011 4.6L Crown Victoria, Grand Marquis).
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: easyautodiagnostics.com).
     
     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 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

You're going to need a multimeter to test the resistance of each fuel injector. Now, you don't need a really fancy multimeter. Even an analog multimeter will do. If you don't have one and need to buy one and don't want to spend an arm and a leg on it, check out my recommendation here: Buying A Digital Multimeter For Automotive Diagnostic Testing (at: easyautodiagnostics.com).

NOTE: The resistance specification for the fuel injectors on your 4.6L V8 are with a cold engine. So if the engine in your Crown Victoria (Grand Marquis) has been running for any length of time, let it cool down completely. The warmer/hotter the fuel injector is, the more the resistance value will differ from the one given in the specification.

These are the test steps:

1. 1

   Disconnect the fuel injector from its electrical connector.
   
   NOTE: The illustration above will help you identify the cylinder the fuel injector belongs to.

2. 2

   Place your multimeter in 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).
   
   You should see a resistance value between 11 to 18 Ohms (with the engine completely cold).
   
   Measure the resistance of the same fuel injectors several times so that you can be sure of your multimeter's Ohms result.

4. 4

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

5. 5

   Repeat steps 2 through 5 on any other fuel injector you need to test.

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

CASE 1: One or more of the fuel injectors show a different resistance value than the one given in the specification (11 to 18 Ohms). This test result tells you that those fuel injectors, that don't have the indicated resistance value, have an internal problem with their coil winding. You'll need to replace them.

CASE 2: All the fuel injector resistances are within the value given in the specification. This test result tells you that the fuel injectors don't have a problem with their internal coil winding. In other words, they're not shorted or have an open. There's still a good chance that the fuel injectors might be clogged. My suggestion to you is to go on to the next subheading: PART 2: Checking The Fuel Injector Spray Pattern.