How to Test a BAD Fuel Injector (2.6L Isuzu Pick Up)

If you've been wondering how to test the fuel injectors on your 1993-1997 1.6L equipped Toyota Corolla (1993-1997 1.6L Geo Prizm), then you've come to the right place. In this tutorial, I'll explain how to check for a bad fuel injector by doing a simple multimeter resistance test.

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 article at a quick glance:

  1. Symptoms of Bad Fuel Injector.
  2. Checking the Injector's Internal Resistance.
  3. How to Find the BAD or Clogged Fuel Injector.
  4. Where to Buy the Fuel Injector and Save.
  5. More 1.6L Toyota Tutorials

Symptoms of Bad Fuel Injector

The two most common types of fuel injector failure are: a clogged fuel injector that doesn't atomize fuel correctly and an completely fried injector that doesn't spray any fuel.

Testing for a fail injector that has stopped injecting fuel because its internal winding is shorted simply involve a multimeter resistance test (and this is the focus of TEST 1).

Well, since your Toyota's 1.6L engine's cylinders need fuel, spark and air to produce power... when the fuel injectors stops spraying fuel... you'll have bona-fide misfire on your hands.

Here are some more symptoms you'll see/experience:

  1. Rough idle.
  2. Lack of power.
  3. Hesitation when you accelerate your 1.6L Toyota Corolla (Geo Prizm) down the road.
  4. Misfire trouble codes (OBD II equipped only):
    1. P0300: Random Cylinder Misfire.
    2. P0301: Cylinder #1 Misfire.
    3. P0302: Cylinder #2 Misfire.
    4. P0303: Cylinder #3 Misfire.
    5. 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

How to Test a BAD Fuel Injector (1.6 Toyota Corolla -1.6L Geo Prizm)

What makes testing the fuel injectors on the 1.6L engine is that they are very accessible. What we'll do, is check the internal resistance of each fuel injector and match that up to the factory fuel injector specification.

If a fuel injector is fried, you'll see that its resistance value won't match the factory spec and that its resistance value is drastically different from the others.

The test steps below assume that you're testing all four fuel injectors.

  1. 1

    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 1.6L Toyota.

  2. 2

    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).

  3. 3

    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.

  4. 4

    Repeat steps 1 through 3 on the remaining fuel injectors.

    NOTE: The 1.6L Toyota resistance specification is: 13.4 to 14.2 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... 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.