A bad or clogged fuel injector can cause a rough idle or a misfire that will light up your check engine light and cause engine performance problems.
The good news is that testing the fuel injectors simply involves testing their internal coil winding's resistance with a multimeter. The bad news is that the plastic intake manifold has to be removed to access them on your 3.0L Ford Escape. This doesn't mean they can't be tested, it simply means that there's a few more steps involved.
In this tutorial I'll explain the fuel injector resistance test and I'll give you some important tips you need to keep in mind when removing the intake manifold plenum. I'm also gonna' offer you a specific diagnostic guide to finding the bad (or clogged) fuel injector in case you don't know where to start your troubleshooting efforts (in page 2 of this tutorial).
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar los Inyectores de Combustible (2001-2004 3.0L Ford Escape) (at: autotecnico-online.com).
Symptoms Of A Bad Fuel Injector
The majority of fuel injector problems usually fall into one of two categories. In the first one, the fuel injector stops injecting fuel because it has fried internally. In the second, the fuel injector gets clogged and doesn't inject enough fuel.
Here's a basic list of the most common symptoms you'll see when a fuel injector fails by either not injecting fuel or by getting clogged:
- Rough idle.
- Lack of power.
- Hesitation when you accelerate your 3.0L Ford Escape 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.
- P0305: Cylinder #5 Misfire.
- P0306: Cylinder #6 Misfire.
The focus of this tutorial is to see if the fuel injector's internal coil has failed (and thus causing the fuel injector to stop injecting fuel) but testing for a clogged injector isn't that much more complicated and I'll show you how in the next page.
Checking The Injector's Internal Resistance
As mentioned at the beginning of this tutorial, we're gonna' test the fuel injectors' internal coil winding. If a fuel injector's winding is fried (either because it's shorted or is open), its resistance value will not coincide with the factory resistance specification. This spec is 13.1 to 14.5 Ohms (Ω), although some Ford manuals mention 11 to 18 Ohms as acceptable.
By the way, it's very common to find that some of the fuel injector pigtail connectors are broken and making a false connection (leading to a misfire condition) or that a connector's locking tab breaks when you unplug it. If you find this to be the case in your particular situation, you can buy new ones here: Where To Buy The Fuel Injector And Save.
NOTE: If you haven't already, take a look at this section before removing the intake manifold plenum: Precautions to Take When Removing the Plastic Intake Manifold Plenum.
Alright, let's get started:
Disconnect the fuel injectors from their harness connectors.
NOTE: To identify which cylinder the fuel injector belongs to, the above illustration of the engine block with the cylinder numbers will help you.
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 in the image viewer).
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 3.0L Ford Escape resistance specification is: 13.1 to 14.5 Ohms (or 11 to 18 Ohms).
Let's find out what your specific multimeter test results mean:
CASE 1: The fuel injector resistance of all 6 was within specification (or similar). This confirms that the fuel injectors are OK. Specifically, that none are shorted or open internally.
Here's why: If any one of the fuel injectors were shorted or open internally, the fuel injector would have registered a radically different resistance value on your multimeter. Since the resistance values for a 6 were uniform, this test result tells you that they are not defective.
Your next step is to go to the next page and see the troubleshooting guide here: How To Find The Bad Or Clogged Fuel Injector.
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.