How To Test The Fuel Injectors (1990-1997 2.3L Ford)

When a fuel injector on your 2.3L Ford Ranger (Mustang or Mazda B2300) fails, its internal resistance changes drastically.

This makes it easy for you and I to test it by simply measuring its internal resistance (and comparing it to what the factory specification is) and I'll show you how in this tutorial.

In case you don't know how to find the bad fuel injector, I'm also going to show you a simple fuel injector diagnostic strategy that will help you find it.

You can find this tutorial in Spanish here: Cómo Probar Los Inyectores De Combustible (2.3L Ford) (at: autotecnico-online.com).

Symptoms Of A Bad Fuel Injector

A fuel injector fails in one of several ways. It either:

1. Stops injecting fuel completely.
2. It doesn't inject enough fuel because its clogged.
3. It over injects due to electrical issues.

No matter how the fuel injector fails, the symptoms are pretty much the same ones. These symptoms are:

• Rough idle.
• Lack of power.
• Hesitation when accelerating the vehicle down the road.
• Misfire trouble codes (OBD II equipped only):
  • P0300: Random Cylinder Misfire.
  • P0301: Cylinder #1 Misfire.
  • P0302: Cylinder #2 Misfire.
  • P0303: Cylinder #3 Misfire.
  • P0304: Cylinder #4 Misfire.

Although this tutorial concentrates on testing a fuel injector that has completely failed, testing a clogged fuel injector isn't that much more complicated and I'll also show you how to diagnose such a condition.

The Fuel Injector Resistance Test

As I mentioned at the beginning of the tutorial, testing a bad fuel injector involves testing its internal resistance.

The internal resistance test checks for a fried fuel injector that has stopped injecting fuel completely and is a very accurate test.

The instructions below assume that you're testing all four fuel injectors on your 2.3L Ford Ranger (Mustang or B2300).

Alright, here are the steps:

1. 1

   Disconnect the fuel injectors from their harness connectors.
   
   You don't have to test them all but I suggest you do.

2. 2

   Set your multimeter to Ohms mode and:
   
   measure the resistance of the fuel injector across its two male spade terminals with the multimeter test leads.

3. 3

   You should see the following resistance:

   1. 2.3L Ford Ranger
      1. 1990-1993 fuel injector resistance: 15 to 18 Ωs.
      2. 1994-1997 fuel injector resistance: 11 to 18 Ωs.
   2. 2.3L Ford Mustang
      1. 1990-1991 fuel injector resistance: 15 to 19 Ωs.
      2. 1992-1993 fuel injector resistance: 13 to 16 Ωs.
   3. 2.3L Mazda B2300
      1. 1994 fuel injector resistance: 12 to 16 Ωs.
      2. 1995-1997 fuel injector resistance: 11 to 18 Ωs.
4. 4

   Repeat steps 1 through 3 on the remaining fuel injectors.

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

CASE 1: All fuel injectors registered the same resistance values. This confirms that the fuel injector your are testing is OK.

Here's why: If any one of the fuel injectors were bad, your multimeter would've registered a completely and totally different resistance value (for that fuel injector). Since your resistance (Ohms) Value were the same for all, this is an indication that the fuel injectors do not have an internal electrical fault.

CASE 2: One of the fuel injectors registered a completely different resistance value. This indicates that the fuel injector is bad. Replace the fuel injector.