How To Test A BAD Fuel Injector (1993-1999 2.0L Mazda 626, 1993-1997 2.0L Mazda MX6)

If you suspect that a fuel injector has stopped working and is behind the misfire (or rough idle) on your 1993-1999 2.0L Mazda 626, 1993-1997 2.0L Mazda MX6, then this tutorial will help you find out.

Since the fuel injectors on the 2.0L Mazda 626 and MX6 are easy to get to, testing them isn't hard. Now, in case you're wondering what's involved in testing the fuel injectors, let me tell you that you'll need to make sure its internal coil winding resistance is within specification (with a multimeter).

Contents of this article at a quick glance:

  1. Symptoms of Bad Fuel Injector.
  2. Checking The Injector's Internal Resistance.
  3. How To Find The Bad Or Clogged Fuel Injector.
  4. Where To Buy The Fuel Injector and Save.

Symptoms Of A Bad Fuel Injector

Having the fuel injector's internal coil winding short out is one of the most common type of fuel injector failures. The other is a clogged fuel injector that can no longer spray (atomize) fuel in a correct conical pattern.

Since a fuel injector injects the gasoline the cylinder needs to produce power, when one fails (or gets clogged) it'll have serious repercussions in engine performance. Here are the most common symptoms you'll see when a one fails:

  1. Rough idle.
  2. Lack of power.
  3. Hesitation when you accelerate your Mazda 626 down the road.
  4. Misfire trouble codes:
    1. P0300: Random Cylinder Misfire.
    2. P0301: Cylinder #1 Misfire.
    3. P0302: Cylinder #2 Misfire.
    4. P0303: Cylinder #3 Misfire.
    5. P0304: Cylinder #4 Misfire.

The test I'm gonna' show you deals primarily with shorted fuel injector coil windings. But, I'll also offer you a specific diagnostic strategy to find a clogged fuel injector (in the next page, heading: How To Find The Bad Or Clogged Fuel Injector)

Checking The Injector's Internal Resistance

Checking The Injector's Internal Resistance With A Multimeter. How To Test A BAD Fuel Injector (1993-1999 2.0L Mazda 626, 1993-1997 2.0L Mazda MX6)

As I mentioned at the beginning of this tutorial, we're gonna' check that the internal fuel injector's coil winding isn't shorted or open by doing a simple multimeter resistance test.

The factory fuel injector resistance for the 1993-1999 2.0L Mazda 626, 1993-1997 2.0L Mazda MX6 is 12 to 16 Ohms ().

NOTE: Your fuel injector resistance test should be done with your Mazda's engine cold. If the engine has been running for any extended length of time, let it cool down completely.

These are the test steps:

  1. 1

    Disconnect the fuel injectors from their engine wiring harness connectors.

    NOTE: To identify which cylinder the fuel injector belongs to, see the above illustration with the cylinder # id for the 2.0L Mazda 626 (MX6).

  2. 2

    Set your multimeter to Ohms (Ω) mode and:

    Measure the resistance of the fuel injector across its two male spade terminals with the multimeter test leads (see the illustration above).

  3. 3

    Write down the resistance value that your multimeter records for the specific fuel injector you're testing. The illustration above will help you identify the cylinder # the fuel injector belongs to.

  4. 4

    Repeat steps 1 through 3 on the remaining fuel injectors.

    NOTE: The fuel injector resistance specification is: 12 to 16 Ohms.

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


CASE 1: Your test results confirm that all fuel injectors' resistances are within specification. This is the expected and correct test result and tells you that none are shorted or open internally.

If you suspect that you have a clogged fuel injector, which a resistance test won't find, take a look at the following section: How To Find The Bad Or Clogged Fuel Injector.

CASE 2: One of the fuel injectors registered a resistance value not within the specification. This indicates that the fuel injector is BAD. Replace the fuel injector.