How To Test The Fuel Injectors (1992-1994 3.0L Ford Ranger)

This tutorial will explain how to test the resistance of the fuel injectors on the 1992, 1993, and 1994 3.0L Ford Ranger.

This is a very simple test that's done with a multimeter in Ohms mode. The test itself isn't hard to do but what complicates the entire procedure is that the intake manifold plenum has to be removed to test the resistance of the 1, 2, and 3 cylinder fuel injectors.

NOTE:This tutorial also applies to the 1992 , 1993, and 1994 3.0L Ford Aerostar.

You can find this tutorial in Spanish here: Cómo Probar Los Inyectores (1992-1994 3.0L Ranger) (at: autotecnico-online.com).

Symptoms Of A Defective Fuel Injector

As you are probably already aware, each cylinder in your 3.0L Ford Ranger's engine needs three things to produce power. These are air (compression), fuel, and spark. So when a fuel injector goes bad, and it stops injecting fuel, that cylinder will misfire.

Generally you're going to see one or several of the following when a fuel injector is bad:

• Rough idle.
• Cylinder misfire.
• Lack of power as you accelerate your Ford Ranger under load.

What usually causes a fuel injector to go bad is one of the following:

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 are 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

The fuel injectors on the Ford Ranger (Ford Aerostar) are not too expensive. You can save further by shopping online for them:

Not sure if the fuel injectors above fit your particular 3.0L Ford Ranger? Don't worry, once you get to the site, they'll ask you for the specifics of your Ford and make sure they fit.

Testing The Fuel Injector Resistance

Testing the cylinders 4, 5, and 6 fuel injectors is a piece of cake. Now what complicates things a bit, is the fact that the fuel injectors for cylinders 1, 2, and 3 are located beneath the intake manifold plenum.

To be able to access these three, you need to remove the intake manifold plenum. Although I'm not providing instructions on how to do this I do have a few helpful suggestions for you. You can find them here: The Intake Manifold Plenum Has To Be Removed.

NOTE: The following fuel injector wiring diagram may come in handy: 1992-1994 3.0L Ford Ranger Fuel Injector Wiring Diagram.

1. 1

   Disconnect the fuel injectors from their harness connectors.
   
   NOTE: To identify which cylinder the fuel injector belongs to, see the above illustration with the cylinder # id.

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.

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 1992-1994 Ford Ranger injector resistance specification is: 13 to 19 Ohms.

Let's analyze your multimeter test results:

CASE 1: The fuel injector resistances are within specification. This is the correct test result and lets you know that the fuel injectors do not have an internal short-circuit or open-circuit.

With this test result you can conclude that the fuel injector (you tested) does not have an internal short-circuit or open-circuit condition and that it's not the cause of the misfire.

CASE 2: One or more fuel injectors did not register the indicated specification of 13-19 Ohms. This test result tells you that the fuel injector that did not register the indicated specification is defective.