How To Test The Fuel Injectors (1990-1997 2.3L Ford)

Fuel Injector Diagnostic Strategy

Finding the bad fuel injector or a fuel injector that's clogged (and thus not spraying fuel) is not hard to do, if you have a specific diagnostic strategy. In this section, I'm gonna' share with you my way of diagnosing a fuel injector that will work in any DIY environment.

I first start by:

1. Identifying the misfiring (or ‘dead’ cylinder) first.
   • If your Ford Ranger or Mazda B2300 is OBD II equipped, this can easily be done by checking for misfire trouble codes with a scan tool.
   • You won't always have a specific bad fuel injector code, but you'll definitely have a misfire code (around 90% of the time that is).
   • If no codes are present, then the next best thing to do is a cylinder balance test. This test test is done by simply unplugging one fuel injector at a time, while the engine is running to see if it unplugging it worsens the engines idle.
     • If the engine idle DOES NOT get worse, then that cylinder is ‘dead’ and is the one causing the misfire.
     • If the idle DOES get worse, then that cylinder is OK and not the cause of the misfire.
2. Check the ignition system for spark.
   • After finding the ‘dead’ cylinder, it's important to make sure that each and every engine cylinder is getting spark.
   • It's important that you check that the spark plug boot and spark plug are NOT soaked (or swimming) in engine oil.
   • You should also remove the spark plugs and check them for cracks or carbon tracks (this is SO important).
     • Here's a real life case study on carbon tracks and how they can cause a misfire: Carbon Tracks Are A Common Cause Of Ignition Misfires (at: easyautodiagnostics.com).
3. Check engine compression.
   • After making sure that the ignition system and all its components are OK, you need to check for low engine compression.
   • This is one of the most overlooked tests when diagnosing a misfire or rough idle condition.
   • You can find the test here: How To Test The Engine Compression (2.3L Ranger, Mustang, B2300) (at: easyautodiagnostics.com).
4. Noid light test.
   • If every test above checks out OK, then the next step is to do a fuel injector Noid light test.
   • The Noid light test will help you make sure that the fuel injector is being activated.
   • The following Noid light article/tutorial may help you: How To Use A Noid Light And Where To Buy It (I know that this is not the most in-depth article on the subject, but it should give you an idea of what is involved).
5. Swap the fuel injector with its neighbor on the fuel injector rail.
   • If I've found out that I have a specific ‘dead’ cylinder, I'll swap out the fuel injector if:
     1. The ignition system is not at fault.
     2. The cylinder's compression value is good (compared to the rest of the cylinders).
     3. The fuel injector resistance is good
     4. I think the fuel injector is clogged.
     If the misfire now follows that swap, I now know that fuel injector is clogged (or bad) and needs to be cleaned or replaced.

The above testing strategy may seem like overkill or too difficult but it isn't. Most of the above tests can be done pretty fast and are not hard to do.

I can tell you from experience that the way to save yourself the frustration of replacing good parts, your vehicle doesn't need and that don't solve the problem, is testing everything. Thankfully, there's a test for just about anything on your car!

Where To Buy The Fuel Injector And Save

The following links will help you to comparison shop for the fuel injector on your 2.3L Ford:

Not sure if the above fuel injectors fit your particular 2.3L Ford? Don't worry, once you get to the site, they'll make sure it fits. If it doesn't, they'll find you the right one.

More ‘How To Test’ Tutorials

You can find a pretty big list of 2.3L Ford tutorials in this index: Ford 2.3L Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Diagnose A Misfiring Cylinder (2.3L Ford Ranger, Mustang, B2300).
• How To Test The Engine Compression (2.3L Ranger, Mustang, B2300) (at: easyautodiagnostics.com).
• Test The Ignition Module And Crank Sensor (2.3L Ranger, Mustang, B2300) (at: easyautodiagnostics.com).
• How To Test For A Blown Head Gasket (2.3L Ranger, Mustang, B2300) (at: easyautodiagnostics.com).
• How To Test The Ford Mass Air Flow (MAF) Sensor (at: easyautodiagnostics.com).