You can test a fuel injector, right on the car, to see if it's bad (or not). In this tutorial I'll show you how.
Now, in case you just suspect that you have a bad (or dirty) fuel injector and don't know where to start, I'll also show you a basic diagnostic/troubleshooting strategy that'll help you get to the bottom of the problem.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar los Inyectores de Combustible (Ford 1.9L, 2.0L) (at: autotecnico-online.com).
Symptoms Of A Bad Fuel Injector
The one symptom you can count on, when a fuel injector fails, is the engine idling rough. Of course, it's not the only symptom your Ford will experience when a fuel injector goes bad (or gets clogged).
Here are a few more symptoms you may see when the fuel injector isn't spraying fuel into its respective cylinder:
- Rough idle.
- Lack of power.
- Hesitation when you accelerate your 2.0L Ford Escort (Focus) down the road.
- Since the 2.0L Ford Escort (Focus) is OBD II equipped, you'll see a misfire diagnostic trouble code (DTC):
- P0300: Random Cylinder Misfire.
- P0301: Cylinder #1 Misfire.
- P0302: Cylinder #2 Misfire.
- P0303: Cylinder #3 Misfire.
- P0304: Cylinder #4 Misfire.
As you're probably already aware, fuel injectors can fail in one of several ways:
- The fuel injector's internal winding shorts out or becomes ‘open’. When this happens, fuel injector stops injecting fuel.
- The fuel injector becomes clogged and doesn't spray correctly or not enough fuel. In tech terms: It doesn't atomize the fuel correctly.
- It comes on and does not turn off (due to electrical issues). In other words: it does not pulse on and off but stays on all of the time spraying a tremendous amount of fuel as soon as you turn the ignition key to the ON position.
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
The fuel injectors on your 2.0L Ford Escort (Focus) have an internal coil winding. When a fuel injector fails, it's usually because this coil winding shorts out.
You and I can check the state of this coil winding (to see if it's shorted or not) by doing a simple multimeter resistance test.
NOTE: Don't have a multimeter or need to upgrade yours? Check out my recommendation: Buying A Digital Multimeter For Automotive Diagnostic Testing.
Alright, here are the steps:
Disconnect the fuel injectors from their harness connectors.
NOTE: The illustration above will help you identify the cylinder # the fuel injector belongs to.
Place your multimeter in 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 2.0L Ford Escort (Focus) fuel injector factory manual resistance specification is approximately: 11 to 18 Ohms.
Let's find out what your specific multimeter test results mean:
CASE 1: All fuel injector resistances are within specification. This tells you that your Ford Escort (Focus) 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 4 were uniform, this test result tells you that they are not defective.
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.