How To Test The Fuel Injectors (2001-2003 4.2L V6 Ford F150)

Testing the fuel injectors on the 4.2L Ford V6 engine can seem like one very impossible task, since they're located under the intake manifold plenum and it needs to be removed it to access them.

Not only that but in the majority of cases, in which a fuel injector is suspected of causing a cylinder misfire, it's really an ignition system component that's at fault.

Keeping this in mind, in this tutorial, I'll outline my diagnostic strategy to help you eliminate a few variables before testing the fuel injectors (in order to avoid removing the upper intake manifold unnecessarily).

You can find this tutorial in Spanish here: Cómo Probar Los Inyectores De Combustible (4.2L Ford F150 And F250) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 4.2L V6 Ford F150: 2001, 2002, 2003.

1997-2000 Fuel Injector Tests: The fuel injector test tutorial for the 1997-2000 4.2L Ford F150 and F250 Light Duty pickups can be found here:

• How To Test The Fuel Injectors (1997-2000 4.2L V6 Ford F150, F250).

E-Series Vans: The fuel injector test tutorial for the 1997-2000 4.2L Ford E150 and E250 vans can be found here:

• How To Test The Fuel Injectors (2001-2003 4.2L V6 Ford E150, E250).

Symptoms Of A Bad Fuel Injector

In a nutshell, a bad fuel injector will cause your 4.2L Ford F150 to misfire at idle and while the vehicle is being accelerated.

This is due to the fact that each cylinder needs air, fuel and spark to produce power. So, when the fuel injector isn't injecting fuel (or not enough), that cylinder will misfire.

Here are some more specific symptoms:

• Rough idle.
• Lack of power.
• Hesitation when you accelerate your 4.2L Ford pickup down the road.
• Since the 4.2L Ford pickup is OBD II equipped, you'll see a misfire diagnostic trouble code (DTC):
  • 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.

The fuel injectors, on your 4.2L Ford F150 can fail in one of several ways:

1. The fuel injector suffers an internal short-circuit or open-circuit problem. When this happens, fuel injector stops injecting fuel.
2. The fuel injector becomes clogged and doesn't atomize the fuel correctly.
3. It comes on and does not turn off (due to electrical issues). In other words: it does not pulse ON and OFF but stays on all of the time spraying a tremendous amount of fuel as soon as you turn the ignition key to the ON position.

Whether the fuel injector is fried internally or clogged, this tutorial will offer you some specific suggestions to help you narrow down the possible solution.

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 (found at: easyautodiagnostics.com).
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. A fuel injector pigtail connector.
   • The pigtail connector comes in handy when testing the resistance of the injectors with the intake manifold plenum installed.
4. 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.
5. Hand Tools.
   • Since half of the fuel injectors are underneath the intake manifold plenum, you'll need hand tools like: socket wrench, extensions, sockets, etc. to remove it.
6. Pen and Paper to write down your fuel injector resistance test results.

Start Here: Diagnostic Strategy

To gain access to test the fuel injectors on your Ford F-Series pickup's 4.2L V6 engine, you'll need to remove the intake manifold plenum (yeah, it's a pain in the neck for sure!).

To save yourself from swapping out parts that might not need replacing (or pulling off the intake plenum when it isn't necessary), you'll need a solid diagnostic plan.

If you're unsure how or where to begin, here's the strategy I use and follow:

1. First, identify the 'dead' cylinder.
   • Pinpointing the 'dead' cylinder right away is super important because it'll save you a lot of troubleshooting time and help you avoid the frustration of replacing parts that won't fix the issue (since quite a few things besides a bad or clogged injector can cause a cylinder to misfire).
   • Usually, a cylinder misfire diagnostic trouble code (DTC) will help identify the 'dead' cylinder, but not always. If there's no specific DTC, you might need to perform a manual cylinder balance test.
   • Once you've located the 'dead' cylinder, the next step is to rule out the ignition system as the cause of the misfire.
2. Rule out the ignition system.
   • Check that the 'dead' cylinder is getting a spark. To do this, you'll need to:
     1. Use a spark tester on the spark plug wire to check for spark.
     2. Inspect the spark plug wire for any damage or excessive wear and tear.
     3. Remove and inspect the spark plug for any signs of damage.
   • The ignition system (whether it's the coil pack, spark plug wire, or the spark plug) is responsible for 90% of misfires, so it's best to eliminate it as a cause from the start.
   • You can find the ignition system tests here: How To Test The Ignition Coils (2001-2008 4.2L V6 Ford F150).
   • If the cylinder is getting spark, the spark plug wire is OK, and the spark plug doesn't show any signs of damage, the next step would be to test that cylinder's compression. If you find that the cylinder isn't getting spark, then you've found the issue causing the cylinder misfire.
3. Compression test the 'dead' cylinder.
   • You don't have to test all 6 cylinders, just testing the 'dead' cylinder plus two others (to compare your compression test results to) is enough to get an idea of the internal health of that cylinder.
   • You can find the test explained here: How To Test Engine Compression (1997-2008 4.2L V6 Ford F150, F250).
   • If the 'dead' cylinder has good compression, the next step is to test the fuel injector's resistance. If it doesn't have compression, then you've found the cause of the cylinder misfire issue.
4. Test the fuel injector.
   • The first thing is to test the internal resistance of the fuel injector of the 'dead' cylinder.
   • 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.

I've used the above diagnostic strategy with a ton of success and I think it'll help you too.

Where To Buy The Fuel Injector And Save

The following links will help you comparison shop for the fuel injector on your 4.2L V6 Ford pickup:

Not sure if the above fuel injectors fit your particular 4.2L Ford pickup? 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.

PART 1: Checking The Injector's Internal Resistance

OK, as you're already aware, the upper intake manifold plenum has to be removed to access the fuel injectors. Although I don't include any R and R (remove and replace) info, I do have a few suggestions for you before you start. You can read them here:

• Precautions When Removing The Upper Intake Plenum.

One more thing: Testing the resistance of certain fuel injectors can be challenging due to their location. This can make it tricky to probe their male spade terminals with the multimeter leads for a resistance measurement.

I've found that the best way to tackle this is by using a fuel injector pigtail connector (which I buy online). I attach the pigtail connector to the fuel injector and then measure the resistance by probing the exposed wire ends of the connector.

With this method, not only do I guarantee getting an accurate measurement, but I also avoid the hassle of not having direct access to the injectors' male spade terminals.

NOTE: Don't have a multimeter or need to upgrade yours? Check out my recommendation: Buying A Digital Multimeter For Automotive Diagnostic Testing.

Alright, here are the steps:

1. 1

   Remove the intake manifold plenum.

2. 2

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

3. 3

   Place your multimeter in Ohms (Ω) mode.

4. 4

   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 8.5 to 15.5 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.

5. 5

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

6. 6

   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: The resistance of the 'dead' cylinder's fuel injector is within specification. This tells you that this particular fuel injector doesn't have an internal short or open-circuit problem.

Your next step is to check that the fuel injector isn't clogged. Go to: PART 2: Checking The Fuel Injector Spray Pattern.

CASE 2: The resistance of the 'dead' cylinder's fuel injector IS NOT within specification. This tells you that the fuel injector is bad. Replace the fuel injector.