This tutorial will help you to test the internal resistance of the fuel injectors on the 1994-1995 3.8L V6 Ford Mustang. This tutorial also covers the 1994-1995 3.8L V6 Ford Thunderbird and 1994-1995 3.8L V6 Mercury Cougar.
The resistance test is done with a multimeter. You don't need any type of fancy or expensive diagnostic equipment to test the fuel injectors on your Ford Mustang.
The only thing that complicates the fuel injector test on the 3.8 V6 Ford Mustang engine is the fact that the injectors for cylinders for five and six are underneath the intake manifold plenum (also known as the upper intake manifold).
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar Los Inyectores (1994-1995 3.8L Ford Mustang) (at: autotecnico-online.com).
Symptoms Of A Bad Fuel Injector
The most obvious symptom of a bad fuel injector or a clogged fuel injector is an engine cylinder misfire. You are going to notice this cylinder misfire when the engine is idling or when it's being accelerated under load. Besides the cylinder misfire, you're going to notice one or more of the following symptoms:
- Rough idle.
- Lack of power when you accelerate your Ford Mustang on the road.
- If your vehicle is OBD2 equipped, you're going to see one or more of the following cylinder misfire 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.
- Bad gas mileage.
Now, when a fuel injector fails, it'll usually fail for one of the following reasons:
- The fuel injectors internal coil winding suffers a short-circuit or an open circuit. When this happens, the fuel injector stops injecting fuel completely.
- The fuel injector becomes clogged and doesn't have them eyes the fuel correctly or doesn't inject enough fuel.
- The fuel injector comes on and stays on due to a short in the wiring or a defect inside the fuel injection computer.
In this tutorial we're gonna' focus on testing the internal resistance of the fuel injector coil. I'm also going to offer you some suggestions on how to find the defective or clogged fuel injector in the next page.
Testing The Fuel Injector's Resistance
Each fuel injector in reality is a solenoid. And as such, each fuel injector has an internal coil winding. When this winding is energized with current, the fuel injectors pintle is opened and fuel is atomized (injected into the cylinder).
Sooner or later, the coil winding will suffer some sort of failure. And when this happens, the fuel injector will stop injecting fuel even though it's getting power and the activation Pulses from the fuel injection computer.
Fortunately, you and I can test the state of the fuel injector's coil winding by doing a simple multimeter resistance test.
NOTE: To be able to test cylinder 4, 5, and 6 fuel injectors (on your 3.8L Ford Mustang, or 3.8L Ford Thunderbird, or 3.8L Mercury Cougar), you'll need to remove the intake manifold plenum. Although I don't have any remove and replace instructions (on how to do it), I do have some very important suggestions that you should take a look at here: On Removing The Intake Manifold Plenum.
Alright, these are the test steps:
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 1994-1995 3.8L Ford Mustang (Thunderbird and Mercury Cougar) 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 injector or fuel injectors you just tested do not have an internal short-circuit or open-circuit.
If your 3.8L V6 has a misfire, this test result tells you that it's not due to an internally defective fuel injector.
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.