Interpreting The Results Of The Fuel Injector Test

Alright, with the resistance values of all six fuel injectors on paper, let's interpret your results. Choose from one of the following CASES:

CASE 1: All of the multimeter resistance values are nearly identical. This result indicates that the fuel injectors are OK and are not causing the misfire code or misfire condition.

If you did have one bad fuel injector in the whole bunch, you would get a drastically different Ohms value in one of them. For example, if 5 of the 6 measured 11.5 to 11.9 Ohms and the sixth one measured 4 Ohms. Well, the one measuring the 4 Ohms is the one that's fried.

CASE 2: One of the six multimeter resistance values is drastically different. Retest the one or more fuel injectors that gave you the drastically different value. If your multimeter still show the same Ohms values, then that or those fuel injectors that registered the drastically different Ohms value are bad.

Which Fuel Injector Do I Test First? Or Do I Test All Of Them?

You don't have to test all fuel injectors. For example, you might have cylinder #4 misfiring or dead and you want to just test that particular fuel injector, well that's OK.

My suggestion is to test the two adjacent fuel injectors so that you can have at least two other resistance (Ohms) value to compare the one you suspect as bad.

If you don't have a specific misfire code to go on, well that's OK too. Just test all of the fuel injectors.

Now, let's say that the one you want to test is under the intake manifold plenum and you need to remove it to get to it. In this situation you can also only test the one you think is bad and at least two others, instead of all of them.

Important Tips

How To Test The Fuel Injectors (Ford 3.0L, 3.8L)

If you do have to remove the intake manifold's plenum, to get to the three fuel injectors underneath it, you need to keep in mind several important things:

  1. 1

    Be careful that no foreign object, like a bolt, a nut, or any metal piece/part, falls into the open manifold port runners.

  2. 2

    Once the plenum has been removed, place a clean rag or rags on the open intake runners. This will keep things from falling into them.

  3. 3

    As you're removing bolts, nuts and stuff from the intake plenum to remove it, place them in a container and away from the engine compartment.

Anything falls into the open intake runners, without you knowing, and the engine is started, you are going to be in a big world of hurt! So be alert and be careful. Removing the plenum is not a thing done on Mars only. It's done around the country in many shops without complications or unhappy endings by simply following some precautions.

A Fuel Injector Troubleshooting Strategy

If you don't know where to start your troubleshooting, testing the fuel injectors can seem a challenge. So, in an effort to help you find the cause of the engine miss (or ‘dead’ cylinder, misfire, etc.) and save some time and money, in this section, I'm gonna' offer you my fuel injector troubleshooting strategy.

Don't worry, it's a simple diagnostic strategy that will maximize your chances of ‘hitting the nail on the head’ and replacing just the part that's causing the problem.

This is how I start:

  1. Find the ‘dead’ cylinder first. This is the most important step of all!
    • Normally, this can be accomplished by simply checking for the misfire codes.
    • If no misfire codes and/or your Ford 3.0L/3.8L equipped vehicle is not OBD II equipped (and thus no misfire diagnostics), then it's important to do a manual cylinder balance test.
  2. The next step is to make sure that the ‘dead’ cylinder is getting spark (and thus eliminate the ignition system as the source of the problem).

Continued in the next page.

Ford Vehicles:

  • Aerostar 3.0L
    • 1992, 1993, 1994, 1995, 1996, 1997
  • Mustang 3.8L
    • 1997, 1998, 1999, 2000, 2001, 2004
  • Probe 3.0L
    • 1990, 1991, 1992
  • Ranger 3.0L
    • 1991, 1992, 1993, 1994, 1995, 1996, 1997

Ford Vehicles:

  • Taurus 3.0L, 3.8L
    • 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Tempo 3.0L
    • 1992, 1993, 1994
  • Thunderbird 3.8L
    • 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997

Lincoln Vehicles:

  • Windstar 3.0L, 3.8L
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003

Lincoln Vehicles:

  • Continental 3.8L
    • 1989, 1990, 1991, 1992, 1993, 1994

Mercury Vehicles:

  • Cougar 3.8L
    • 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
  • Sable 3.0L, 3.8L
    • 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Topaz 3.0L
    • 1992, 1993, 1994

Mazda Vehicles:

  • B3000 3.0L
    • 1994, 1995, 1996, 1997