Testing the fuel injectors on your 2.4L SOHC equipped Mitsubishi Galant (Eclipse or Expo) is easier than you think. In this tutorial, I'll show you how to test them to find out if they are fried (or not).
In case you suspect a bad fuel injector is behind your 2.4L Mitsubishi's rough idle (misfire) but don't know where to start, I'll show you a simple diagnostic 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 (2.4L Mitsubishi) (at: autotecnico-online.com).
Symptoms Of A Bad Fuel Injector
When a fuel injector fails, it'll usually do one of two things: stop injecting fuel completely or inject fuel without atomizing it correctly (as in the case of a clogged injector).
Since each cylinder in your Mitsubishi's 2.4L engine needs air, fuel, and spark to produce power; when a fuel injector fails you'll have a bona-fide misfire on your hands. This misfire will light up the check engine light with a misfire code stored in the PCM's (Powertrain Control Module's) memory.
You'll see one or more of the following symptoms:
- Rough idle.
- Lack of power.
- Hesitation when you accelerate your 2.4L Mitsubishi down the road.
- Misfire trouble codes:
- P0300: Random Cylinder Misfire.
- P0301: Cylinder #1 Misfire.
- P0302: Cylinder #2 Misfire.
- P0303: Cylinder #3 Misfire.
- P0304: Cylinder #4 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
What we'll do, to find out if you have a bad fuel injector, is to check the internal resistance of each fuel injector.
If you've got a bad fuel injector, then its resistance value will be drastically different from the others or from the factory specification.
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 for the 2.4L engine.
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 above).
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 2.4L Mitsubishi resistance specification is: 13 to 16 Ohms.
Let's find out what your specific multimeter test results mean:
CASE 1: The fuel injector resistance of all 4 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 4 were uniform then 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.