How To Test The Fuel Injectors With A Multimeter (GM 2.2L)

Fuel Injector Troubleshooting Guide

Testing the fuel injectors on the 2.2L GM engines isn't exactly a ‘walk in the park’. Sometimes when you and I think it's a fuel injector causing the misfire, it's really something else causing the problem.

So, if you think you have a bad fuel injector but aren't quite sure where to start, in this section I'm gonna' offer you a few tips. The following guide will help you get to the bottom of the problem, whether it's caused by a bad fuel injector or something else.

OK, the most important thing you need to do first is identify the ‘dead’ cylinder. Because if you do have a bad fuel injector on your hands, your GM 2.2L equipped car will have a misfiring cylinder.

These are the steps I take:

1. Check for misfire codes.
   • Unfortunately, the PCM usually doesn't set a specific bad fuel injector code, but when a fuel injector does go bad, you WILL see a misfire code.
   • The idea here is to find the ‘dead’ cylinder. Now, if you have no misfire codes and yet the engine in your GM 2.2L equipped car is misfiring, then you need to do a manual cylinder balance test.
   • A cylinder balance test involves disconnecting one fuel injector at a time, while the engine is running, to see which one (when disconnected) has NO EFFECT on the engine's idle. The one, when unplugged, that doesn't cause the engine's idle to get worse is the one that belongs to the ‘dead’ cylinder.
2. The next step is to check for spark.
   • It's very important to eliminate the ignition system as the root cause of the misfire or ‘dead’ cylinder.
   • What I'm looking for here is that spark is actually reaching the spark plug. This is accomplished using a dedicated spark tester on the spark plug wire.
   • The following tutorial will guide you step-by-step thru' the whole procedure: How To Test The GM 2.2L Ignition Coil Pack (at: easyautodiagnostics.com).
3. Next, I remove the spark plugs and visually inspect them.
   • What I'm checking for are for cracks and/or carbon tracks and/or oil filling up the spark plug well.
   • The other thing that I'm looking for is to see if the spark plug gap is closed off due to carbon deposits (from oil burning).
4. If everything above checks out OK, I then do an engine compression.
   • This is a fast and easy test but is so often overlooked.
   • You can find this test here: How To Do An Engine Compression Test (GM 2.0L, 2.2L, 2.5L).
5. Check fuel injector resistance.
   • I also do a fuel injector Noid light test to make sure that the fuel injector (that belongs to the ‘dead’ cylinder) is getting power and the activation signal from the fuel injection computer.
6. Swap the fuel injector.
   • If after checking all of the above, the 'dead' cylinder is getting spark, its spark plug is OK, it has good compression, and the fuel injector resistance is OK -yet the cylinder is still misfiring, I then swap out the fuel injector with a fuel injector from one of the other cylinders.
   • If the cylinder misfire follows the 'dead' cylinder's fuel injector, I now know without a doubt that that fuel injector is bad and needs to be replaced.
   • IMPORTANT: This step requires buying new fuel injector o-rings to make the swap (yeah, I know, it sucks). Re-using the old o-rings during the swap won't work because they usually tear and cause gasoline leaks.

The purpose of all of the my tests (above) are to eliminate the ignition system and engine mechanical condition first, before attempting to blame or suspect a bad fuel injector.

I can tell you that this diagnostic strategy has saved me from replacing some good fuel injectors and being able to nail down the ones that are bad.

More GM 2.2L Test Articles

What if the fuel injector resistance test indicates that all of the fuel injectors are OK but my Chevrolet (or GMC or Pontiac) car or pick up is still misfiring/running rough? Or diagnostic trouble codes: P0300, P301, P0302, P0303, P0304 are still popping up on my scan tool? Well, the following test articles might help to narrow down the list of possible causes by testing several different things that can and do cause misfires:

• How To Do An Engine Compression Test (GM 2.0L, 2.2L, 2.5L)
• GM 2.2L Fuel Injector Noid Light Test.
• GM 2.2L Misfire Trouble Code Basics.
• How To Test The GM 2.2L Ignition Coil Pack (at: easyautodiagnostics.com).