How To Test The Fuel Injectors (1997-2000 4.2L V6 Ford E150, E250)

Testing the fuel injectors on the E150/E250 with a 4.2L V6 can seem like a nightmare, since they're located underneath the intake manifold plenum.

I'm not gonna sugarcoated it, it's a challenge, but nothing impossible to do. In this tutorial, I'm gonna share with you the diagnostic process I use to diagnose a bad or clogged fuel injector with some basic tools.

APPLIES TO: This tutorial applies to the following vehicles:

• 4.2L V6 Ford E150: 1997, 1998, 1999, 2000.
• 4.2L V6 Ford E250: 1997, 1998, 1999, 2000.

The fuel injector tests for the 2001-2003 4.2L V6 Ford E150/E250 can be found here:

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

WIRING DIAGRAM: The fuel injector wiring diagram for this tutorial can be found here:

• Fuel Injector Circuit Wiring Diagram (1997-1999 4.2L V6 Ford E150, E250)

F-SERIES PICKUPS: The fuel injector troubleshooting tutorial for the 1997-2000 4.2L Ford F150/F250 vans can be found here:

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

The Two Main Types Of Fuel Injector Failures

A fuel injector will fail in one of the following ways:

• Fuel Injector Suffers An Internal Electrical Failure: The fuel injector's internal winding suffers a short-circuit or open-circuit failure.
• Fuel Injector Gets Clogged: The fuel injector becomes clogged and doesn't atomize (spray) fuel in the correct conical pattern.

When the fuel injector suffers an internal electrical problem, it'll stop injecting fuel and its cylinder is gonna misfire. This type of issue can easily be confirmed with a simple multimeter resistance test.

On the other hand, if the fuel injector gets clogged, even if it's spraying fuel, its cylinder will also misfire. This happens because it isn't atomizing (spraying in a fine mist) the fuel it's injecting into the cylinder. This type of issue can be a little harder to pin-point.

Whether the fuel injector suffers and internal failure or gets clogged, it'll cause the engine to misfire and trigger the check engine light.

Knowing that the majority of fuel injector failures fall within these two categories is winning half the battle.

Symptoms Of A Bad Or Clogged Fuel Injector

As mentioned in the previous section, the most common symptom of a bad or clogged fuel injector is an engine cylinder misfire, but it's not the only one. Other symptoms include, but are not limited to:

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

Now, to go into more specifics of how a fuel injector can fail:

• The fuel injector suffers an internal electrical failure and won't spray any fuel.
• The fuel injector gets clogged and won't spray enough fuel or in the proper spray pattern.
• The fuel injector doesn't activate (spray) because it's not getting power.
• The fuel injector doesn't activate because the fuel injection computer doesn't activate it (although it may be getting power).
• PCM goes bad and activates the fuel injector as soon as the key is turned to the RUN position.

No matter what the root cause, a bad fuel injector will cause the engine to idle rough and miss when you accelerate the van down the road.

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

Testing the fuel injectors on the 4.2L V6 engine requires removing the intake manifold plenum to access them (yeah, I know, this sucks!).

To avoid replacing unnecessary parts (or removing the intake plenum when you don't have to), you need a solid diagnostic strategy.

So if you don't know where to start or just need a troubleshooting 'road map', here's the strategy to follow:

1. Find out which cylinder is the one that's 'dead' first.
   • Locating the 'dead' cylinder from the get-go is the most important/critical first step because it'll save you a ton of troubleshooting time, not to mention avoiding the frustration of replacing parts that don't solve the problem (since so many things can cause a cylinder to misfire besides a bad/clogged injector).
   • In most cases, a cylinder misfire diagnostic trouble code (DTC) is enough to pin-point the 'dead' cylinder, but not always. When there's no misfire DTC identifying a specific cylinder, you may need to do a manual cylinder balance test.
   • After locating the 'dead' cylinder, the next step is to eliminate the ignition system as the cause of the cylinder misfire.
2. Eliminate the ignition system.
   • This means that you need to make sure that the 'dead' cylinder is getting spark. 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 signs of damage.
     3. Remove and inspect the spark plug for any signs of damage.
   • The ignition system (by this I mean either the coil pack, spark plug wire, or the spark plug) is the most common culprit behind 90% of misfires (engine miss), so it's best to eliminate it right from the get-go.
   • You can find the ignition system tests here: How To Test The Ignition Coils (1997-2000 4.2L V6 Ford E150, E250).
   • 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 (1997-2000 4.2L V6 Ford E150, E250)
   • 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.

PART 1: The Fuel Injector Resistance Test

Once you've located the 'dead' cylinder and are sure that the problem isn't caused by an ignition system issue or low compression, the next step is to test the resistance of the fuel injector (that belongs to the 'dead' cylinder).

This is gonna require removing the intake manifold plenum from the engine to access the fuel injectors. I do want to tell you that even with the plenum removed, probing the male spade terminals of some fuel injectors directly with multimeter test leads can still be a challenge.

One way that I've overcome this access issue is by using a fuel injector pigtail connector (I bought it online). I plug it into the fuel injector and then probe its exposed wire ends with the multimeter leads. This approach makes testing them a breeze.

If the resistance of the fuel injector is within specification (11 to 18 Ohms), we'll move on to the next test section and visually check if the fuel injector is actually spraying in a correct way using a spray can of brake cleaner (with an inexpensive specialized tool).

NOTE: If you haven't removed the intake manifold plenum yet, take a look at the following section: Important Tips For Removing And Installing The Intake Manifold Plenum.

Alright, here's the test:

1. 1

   Remove the intake plenum.
   
   IMPORTANT: After removing the intake manifold's plenum, place clean rags in the open intake runners.

2. 2

   Disconnect the fuel injector that you're gonna test from its electrical connector.

3. 3

   Place your multimeter in Ohms mode.

4. 4

   Measure the resistance across the male spade terminals of the fuel injector with the multimeter test leads.
   
   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.

5. 5

   Write this Ohms value down and record the number of the cylinder that fuel injector belongs to.

6. 6

   Repeat test steps on two other fuel injectors.
   
   NOTE: The other two fuel injectors will give you a reading to compare to.

Alright, let's interpret your results:

CASE 1: The resistance value of the 'dead' cylinder's fuel injector is within specification. This result tells you that the fuel injector doesn't have an internal short-circuit or open-circuit problem.

Your next step is to check the fuel injector's spray pattern to see if it's clogged. Go to: PART 2: Checking The Fuel Injector Spray Pattern.

CASE 2: The 'dead' cylinder's fuel injector resistance is not within specification. Test this one injector again. If the injector registers the same Ohm value as before, this injector is defective.