In this tutorial I'll explain how to test the resistance of the fuel injectors on the 1991, 1992, 1993, 1994, And 1995 3.0L Ford Taurus (Mercury Sable).
The fuel injector resistance test is pretty easy and it's done with a multimeter. Now what complicates things a bit is fact that three of the fuel injectors are located beneath the intake manifold plenum.
NOTE: This tutorial also applies to the following vehicles: 1991-1994 3.0L Ford Tempo, 1991-1992 3.0L Ford Probe, and 1991-1995 3.0L Mercury Sable.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar Los Inyectores (1991-1995 3.0L Taurus) (at: autotecnico-online.com).
Symptoms Of A Defective Fuel Injector
A bad fuel injector can cause several different symptoms. What you will usually see is a rough idle condition or a misfire when the engine is idling or accelerated under load.
Here's a brief list of symptoms that you'll see when one or several fuel injectors fail on your 3.0L Ford Taurus (Mercury Sable):
- 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:
- 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.
- The fuel injector becomes clogged and does not atomize the fuel correctly or doesn't inject enough fuel.
- The fuel injector does not activate because it's not getting either power or activation signal from the fuel injection computer.
- 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.
Testing The Fuel Injector Resistance
Okay, if you've done any research on the fuel injectors you know that each one comes equipped with an internal coil winding.
It's when this coil winding gets energized with 12 Volts and Ground that the injector opens up and starts to spray fuel. Sooner or later this coil winding fail and the injector will stop injecting fuel.
The cool thing is is that you and I can test the state of the fuel injector's coil winding to see if it has suffered a short-circuit or an open-circuit problem. And this test can be done with your multimeter in Ohms mode.
What complicates things a bit on the 3.0L Ford Taurus, 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.
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.
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.
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.
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.
Si el embobinado del inyector de combustible no diera una lectura de 13 a 19 Ohmios, entonces pudieras concluir que ese inyector está averiado y por lo tanto está provocando una falla en cilindro.
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.