How To Test The Fuel Injectors (2000-2007 3.0L V6 Ford Taurus, Mercury Sable)

In this tutorial, I'm going to show you how you can easily and quickly find out if you've got a bad fuel injector on your 2000-2007 3.0L V6 Ford Taurus or Mercury Sable.

In a nutshell, we're going to check the internal resistance of all six fuel injectors to see if any of them have an internal short-circuit or open-circuit issue with their winding, which would cause them to stop injecting fuel.

Whether you're troubleshooting a bad or clogged fuel injector, you'll find all of the info you'll need to quickly and easily figure out if a fuel injector is the cause of your cylinder misfire issue or if it's something else.

APPLIES TO: This tutorial applies to the following vehicles:

• 3.0L V6 (OHV) Ford Taurus: 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007.
• 3.0L V6 (OHV) Mercury Sable: 2000, 2001, 2002, 2003, 2004, 2005.

FUEL INJECTOR CIRCUIT DIAGRAM:

• Fuel Injector Circuit Wiring Diagram (2000-2001 3.0L V6 Ford Taurus, Mercury Sable).
• Fuel Injector Circuit Wiring Diagram (2002-2003 3.0L V6 Ford Taurus, Mercury Sable).
• Fuel Injector Circuit Wiring Diagram (2004-2007 3.0L V6 Ford Taurus, Mercury Sable).

Symptoms Of A Defective Fuel Injector

Every cylinder in your Ford Taurus or Mercury Sable's 3.0L V6 engine has got to have three things to be able to function. These are air (compression), fuel, and spark. And you've guessed it, it's the fuel injector that provides the fuel the cylinder needs to function.

When a fuel injector fails, it'll stop injecting fuel altogether or it'll get clogged and not spray fuel in a correct pattern, or it just won't spray enough fuel. Whatever the issue is with the fuel injector, you're going to see one or more of the following engine performance issues:

• Rough idle.
• Lack of power when you accelerate your Ford on the road.
• If your Ford Taurus comes equipped with OBD2, you'll see one of the following 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.

When fuel injectors fail, they usually fail for one of the following reasons:

1. The internal coil winding (of the fuel injector) suffers a short-circuit or an open-circuit. When this happens, the fuel injector will stop injecting fuel completely.
2. The fuel injector becomes clogged and does not atomize the fuel correctly or doesn't inject enough fuel.
3. The fuel injector does not activate because it's not getting either power or activation signal from the fuel injection computer.
4. The fuel injector comes on and stays on due to a short in the wiring for a defective fuel injection computer.

In this tutorial, we're going to focus on testing the internal coil winding of the fuel injectors to see if they are in a short-circuit or open-circuit state. Testing for a clogged fuel injector isn't hard and I'll offer you some suggestions in the next page.

Where To Buy The Fuel Injector

If your test results do confirm you've got a bad fuel injector, I want to make the following recommendation. This fuel injector is from a known automotive brand (Standard Motor Products) that I've used throughout my automotive repair career, and I don't hesitate to recommend it:

NOTE: Not sure if the fuel injector fits your particular Ford Taurus or Mercury Sable? Don't worry. Once you get to the site, they'll ask you for the specifics of your vehicle and check to see if the part fits. If it doesn't, they'll find the right one for you.

Testing The Fuel Injector Resistance

As you're already aware, three of the six fuel injectors are underneath the intake manifold plenum. This really isn't a problem since we can still easily check their internal resistance by probing the correct female terminals at the 104-pin PCM connector.

Now, to be a bit more specific as to what we're going to do, we're going to disconnect the PCM from its 104-pin connector and test the resistance of each fuel injector right at the PCM connector. This effectively helps us avoid removing the plenum to check the injectors for cylinders 1, 2, and 3.

This is a piece of cake to do, but there are certain important precautions you've got to take when probing the female terminals of the PCM connector. I've written a guide that explains this in more detail. Please take a look at it before you begin your tests: How To Safely Probe The PCM Connector -Without Damaging It (1991-2007 3.0L V6 Ford Taurus, Mercury Sable).

Our fuel injector circuit resistance test will give us one of two results:

• Good fuel injector: The resistance your multimeter reports for the fuel injector circuit will be between 11 to 18 Ohms.
• Bad fuel injector: Your multimeter will report a resistance out of the range of 11 to 18 Ohms. You'll usually see either the multimeter reporting an open-circuit issue (infinite Ohms) or a short-circuit issue (0 Ohms).

NOTE: If you don't have a multimeter or you need to upgrade the one you've got, this is the one I use and recommend: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link).

Alright, these are the test steps:

1. 1

   Disconnect the battery's negative cable and leave it disconnected for the entire test.
   
   NOTE: This step is important. Don't move on to the next step without first disconnecting the negative battery cable from the battery.

2. 2

   Disconnect the PCM from its 104-pin connector.

3. 3

   Set your multimeter to Ohms mode.

4. 4

   With your multimeter test leads —and the appropriate tool— probe between the following female terminals of the 104-pin PCM connector:

   • Injector 1: Pins 75 and 71.
   • Injector 3: Pins 74 and 71.
   • Injector 5: Pins 73 and 71.
   • Injector 2: Pins 101 and 71.
   • Injector 4: Pins 100 and 71.
   • Injector 6: Pins 99 and 71.

   NOTE: Use the connector pinout above to locate VPWR (pin 71) and the injector pins.

5. 5

   Write the resistance value down on a piece of paper, and make sure you note which injector that value belongs to.

6. 6

   Your multimeter should report a resistance between 11 and 18 Ohms for each injector circuit.
   
   If the meter shows an open-circuit, a short-circuit, or a resistance outside the 11–18 Ohm range, that injector circuit has a problem.

Let's analyze your multimeter test results:

CASE 1: The fuel injector circuit resistances are within the indicated specification. This test result confirms that both the injector and the wiring connecting the fuel injector to the PCM are in good shape.

Now, this test result only confirms that the fuel injector doesn't have an internal electrical issue, but it doesn't let us know if the injector is clogged. If you're troubleshooting a cylinder misfire and you've pinpointed the misfire issue to this specific cylinder, then head over to How To Find The Bad Or Clogged Fuel Injector for more troubleshooting suggestions.

CASE 2: One or more fuel injector circuits did not register the indicated resistance specification. This test result is letting you know that there's an issue with either the fuel injector or the wiring between the fuel injector and the PCM connector.

The cool thing is that we can further diagnose this issue and find out which of the two it is. Your next step is to check the resistance of the fuel injector directly at its two terminals and visually inspect the condition of the connector and the two wires exiting the connector. For more information on this next diagnostic step, go to: Checking The Injector's Resistance Directly At Its Terminals.

Checking The Injector's Resistance Directly At Its Terminals

If you got a failed test result in TEST 1, then more than likely your multimeter showed you one of the following three readings:

1. An infinite Ohms reading: This tells you that the fuel injector circuit has an open-circuit problem somewhere. The problem could be with the fuel injector or in the wiring between the injector and the PCM connector.
2. A zero Ohms reading: This test result tells you that the fuel injector circuit has a short-circuit problem. The issue could be within the fuel injector itself or in the wiring between the injector and the PCM connector.
3. A resistance value that's out of the normal range (but not infinite or 0 Ohms): This usually indicates an internal problem with the injector itself. You can generally rule out an electrical issue in the wiring between the fuel injector and the PCM connector with this test result.

Since the problem with the fuel injector circuit could be with either the injector itself or its wiring, we've got to do two more things to pinpoint its exact cause:

• Inspect the fuel injector connector and the wires coming out of it.
  • The connector and the two wires coming out of it are a very common failure point. It's super common for the insulation of the two wires to crack and peel right where they exit the connector. When that insulation falls off, the copper strands get exposed and they'll short together —which will give you 0 Ohms result in TEST 1.
• Measure the resistance directly across the injector's two terminals.
  • If the resistance is still out of specification when tested directly at the terminals, then the injector has an internal electrical problem. And honestly, this ends up being the most common cause of the failed reading in TEST 1.

The one thing that complicates inspecting the fuel injector connector and checking the resistance of the fuel injector is that three of them —the ones for cylinders 1, 2, and 3— sit under the intake manifold plenum. To access these injectors, you've got to remove the plenum.

So if the injector circuit that failed TEST 1 belongs to cylinders 1, 2, or 3, then your next stop is the following section: The Intake Manifold Plenum Has To Be Removed.

The Intake Manifold Plenum Has To Be Removed

Checking the resistance of the fuel injector directly at its two terminals is a piece of cake on the injectors for cylinders 4, 5, and 6. This is the bank of cylinders next to the radiator.

What complicates life a bit is checking the ones that are located beneath the intake manifold plenum, and these are the injectors for cylinders 1, 2, and 3.

Removing the intake manifold to check the resistance of those injectors and to visually inspect their connectors isn't that difficult. I've done it many times before and although it's a process, it's very doable. Here are some very important precautions to take so that you can avoid any complications or headaches:

1. Once you've got the plenum off of the engine, you've got to cover the open intake manifold runners with a clean shop towel. The towel will keep anything from falling into the open intake manifold ports while you're performing your checks and tests.
2. Anything you remove from the engine, whether it be a bolt or a nut, place all of these parts away from the engine compartment. This will ensure that nothing falls on top of the intake manifold runners —even if they're covered with a shop towel.
3. When you're reinstalling the plenum, make sure you use new gaskets and install them dry. In other words, don't coat them in any type of sealant (like RTV silicone sealant).

The key thing here is that you want to avoid having anything fall into the open intake manifold ports, because if something does it's gonna end up inside a cylinder. If a metal nut or bolt fell in, when you crank the engine, it's gonna tear into the piston or cylinder head valves.

The only way to remove whatever fell into an open intake manifold port is to remove one or both cylinder heads. This is a nightmare that can be easily avoided by covering the open intake manifold ports once the plenum is off.

How To Find The Bad Or Clogged Fuel Injector

I've been using a simple diagnostic strategy over the years to help me pinpoint the exact cause of a cylinder misfire issue, whether it's caused by a bad or clogged fuel injector or something else.

In this test section, I'm going to share this diagnostic strategy with you and explain it in a step-by-step manner so you can apply it to your particular situation and easily and quickly find out what's going on with the misfiring cylinder.

This strategy comes in handy in those particular cases where a clogged fuel injector is the one wreaking havoc on engine performance.

OK, this is how you can find the culprit behind the cylinder misfire:

1. Identify the dead cylinder:
   • You can quickly and easily identify the dead cylinder by checking for specific cylinder misfire codes with either a code reader or a scan tool.
   • If you don't have a code reader or scan tool, you can always do a manual cylinder bounce test to figure out which cylinder is the dead one.
2. Make sure that the dead cylinder is getting spark:
   • Checking that the cylinder is getting spark by connecting a spark tester to the spark plug wire is a very important step in pinpointing the cause of the cylinder misfire issue. The following tutorials will help you with these spark tests:
     • How To Test The Ignition Coil Pack (1996-2000 3.0L V6 Ford Taurus, Mercury Sable).
     • How To Test The Ignition Coil Pack (2001-2007 3.0L V6 Ford Taurus, Mercury Sable).
   • Along with checking for spark, you've got to check the entire length of the spark plug wire to make sure that it isn't damaged in any way, shape, or form.
   • Remove the spark plug and check it for any damage or heavy wear and tear.
   • Take a good look at the inside of the spark plug boot and the spark plug's porcelain insulator to make sure that carbon tracks haven't formed on their surfaces. If you do find carbon tracks, you've found the source of the cylinder misfire. To find out more about how carbon tracks cause cylinder misfires, take a look at this real-life case study: Carbon Tracks Are A Common Cause Of Ignition Misfires (at: easyautodiagnostics.com).
3. Check that the dead cylinder has good compression:
   • Checking the dead cylinder's compression is an important step that'll help us further pinpoint the cause of the cylinder misfire.
   • I've written a tutorial that'll explains how to perform and interpret a compression test. You can find this step-by-step tutorial here: How To Do And Interpret An Engine Compression Test (1990-2007 3.0L V6 Ford Taurus, Mercury Sable).
4. Check the internal resistance of the dead cylinder's fuel injector:
   • Once I've confirmed that the dead cylinder has spark and that it has good compression, I now focus on testing the resistance of the fuel injector.
   • If the fuel injector's resistance isn't within the indicated specification, it's fried and causing the cylinder misfire problem.
5. Check the fuel injector's spray pattern:
   • Now, by this point, I've confirmed several things. I've identified the dead cylinder. I've made sure it's getting spark and has good compression. I've also checked the fuel injector and its resistance is within specification.
   • The last thing left to do is to remove the fuel injector, and using a handheld adapter, I connect it to a can of brake cleaner spray and check to see its spray pattern (these DIY fuel injector cleaner kits can easily be purchased online).
   • If the fuel injector doesn't spray in a perfect conical pattern or just squirts fuel out, I've got a clogged fuel injector on my hands, and that's what's causing the cylinder misfire.
   • Here's where you can purchase this tool: Universal Fuel Injector Tester and Cleaner Tool Kit (Amazon affiliate link).

As you've noticed, this diagnostic strategy is simply a process of elimination. All that we're doing is making sure that the dead cylinder is getting spark. We're making sure it has good compression. We're checking its fuel injector to make sure it hasn't suffered an internal short-circuit or open-circuit problem.

If all those things check out, our next step is to remove the fuel injector and check its spray pattern. Of course, it sounds easy on paper, but it's a process. Spending the time to check these things will definitely help you save money and avoid the frustration of buying parts that just don't solve the issue.

More 3.0L V6 Ford Taurus Diagnostic Tutorials

You can find a complete list of 3.0L V6 Ford Taurus and Mercury Sable tutorials in this index:

• 3.0L V6 Ford Taurus Index Of Articles.

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

• How To Test The CKP Sensor (2000-2007 3.0L V6 Ford Taurus, Mercury Sable).
• How To Test The Fuel Pump (2001-2002 3.0L V6 Ford Taurus, Mercury Sable).
• How To Test The TPS With A Multimeter (1996-2007 3.0L V6 Ford Taurus, Mercury Sable).
• How To Test The MAF Sensor (2000-2003 3.0L V6 Ford Taurus, Mercury Sable).