How To Test The Fuel Injectors (1995-1996 1.5L Toyota Tercel)

How To Find The Bad Or Clogged Fuel Injector

One of the hardest thing that a DIY'er can come across, when diagnosing a rough idle condition or a misfire, is how to diagnose a bad fuel injector. So, in this section I'm gonna' offer you a testing strategy that has helped me find the cause of the misfire. I think it'll help you.

Here's what I do:

  1. Find the ‘dead’ cylinder first.
    • If your Tercel is OBD II equipped, this can easily be done by checking for trouble codes with a scan tool or code reader.
    • If no codes are registered, the next step is doing a cylinder balance test to find the ‘dead’ cylinder.
  2. Check that all cylinder are getting spark.
    • It's important to make sure that each cylinder is getting spark with a dedicated spark tester.
    • 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).
  3. Check engine compression.
    • After confirming all cylinders are getting spark, 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:
  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.
    • I'll swap out that fuel injector with its neighbor if:
      • I have confirmed the cylinder is getting spark (which means all ignition system components are OK).
      • I have confirmed the cylinder's compression value is good (compared to the rest of the cylinders).
      • I have confirmed the fuel injector resistance is good.
      • I think the fuel injector is clogged.
      If the misfire now follows the swap, I now know that fuel injector is clogged (or bad) and needs to be cleaned or replaced.

The above list of tests seem pretty long, but they are all very doable since the 1995-1996 Tercel engine layout makes all these tests easy. Give this diagnostic strategy a shot, I think it'll help you nail down the exact cause of the problem.

Fuel Injector Wiring Diagram

Fuel Injector Circuit Wiring Diagram (1995, 1996 1.5L Toyota Tercel)

More 1.5L Toyota Tutorials

You can find a complete list of 1.5L Toyota Tercel tutorial in this index:

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

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