How To Test Engine Compression (2004-2006 2.8L Chevrolet Colorado, GMC Canyon)

Testing the engine compression on the 2004-2006 2.8L Chevrolet Colorado or GMC Canyon is easy because the spark plugs are accessible.

So if you need to test the engine's compression, this tutorial will explain how to perform the engine compression test step-by-step.

You'll quickly determine if an engine compression problem is causing a cylinder misfire problem or an engine no-start problem.

You can find this tutorial in Spanish here: Cómo Probar La Compresión Del Motor (2004-2006 2.8L Chevrolet Colorado, GMC Canyon) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 2.8L Chevrolet Colorado: 2004, 2005, 2006.
• 2.8L GMC Canyon: 2004, 2005, 2006.

Symptoms Of Low Or No Engine Cylinder Compression

Generally, engine compression problems cause one of two issues:

1. A cylinder misfire problem.
2. An engine no-start problem.

If the engine compression problem is causing a cylinder misfire problem, you'll see one or more of the following diagnostic trouble codes:

• P0300: Random Cylinder Misfire.
• P0301: Cylinder #1 Misfire.
• P0302: Cylinder #2 Misfire.
• P0303: Cylinder #3 Misfire.
• P0304: Cylinder #4 Misfire.

Besides a misfire trouble code illuminating the check engine light, you'll see one or more of the following symptoms:

• Blue smoke coming out of the tailpipe.
• Rough engine idle that disappears when you accelerate the engine.
• Bad fuel mileage.

Which Compression Tester Should I Buy?

There are lot of engine compression testers to choose from and many places to buy them. I'm gonna' make two recommendations to you:

1) Which one to buy:  The engine compression tester that I have always used is the Actron CP7827 Compression Tester Kit. My only complaint about this engine compression tester is that it does not come with a case to store it in.

TEST 1: Finding The Dead Cylinders

To get going, we're going to test the compression of all four cylinders.

Once you've gotten the compression values, the next section will help you interpret the results to find out if you got a problem on your hands or not.

If you don't have an engine compression tester, you can rent one from your local auto parts store for a small deposit (they'll return it to you once you return the tool) or buy one online.

You can check my compression tester recommendations here: Which Compression Tester Should I Buy?

IMPORTANT: Do not remove the spark plugs if the engine has been running for any amount of time. Removing the spark plugs from a hot engine risks damaging the spark plug hole threads in the aluminum cylinder heads.

OK, these are the test steps:

1. 1

   Unplug and remove all four ignition coils.

2. 2

   Remove the spark plugs. Remember, the engine can not be hot!
   
   When removing the spark plugs, be careful not to drop any of them on the floor, or you run the risk of having the spark plug's porcelain insulator crack and then you'll have a misfire on your hands.

3. 3

   Thread the engine compression gauge into the spark plug hole for the number 1 engine cylinder.
   
   Hand tighten the compression gauge only! Do not use any type of tool to get it tight.

4. 4

   Have your helper crank the engine till the needle on the compression gauge stops climbing.

5. 5

   Record the value at which the needle stopped and the number of the engine cylinder on a piece of paper.

6. 6

   Release the pressure on the gauge and repeat the test one more time.

7. 7

   Repeat steps 3 thru 6 on the remaining cylinders.

Let's examine your test results:

CASE 1: One or two cylinders had a much lower compression value than the others. This could be normal or it could be a problem.

To find out if these low engine compression values are causing an engine performance issue, go to: Interpreting The Compression Test Results.

CASE 2: Three or more cylinders had almost no compression or 0 PSI compression. The engine is not gonna' start with this type of compression test result and usually indicates a severe internal engine problem.

I recommend doing a wet compression test on these cylinders to find out if the problem is in the block or cylinder head. Go to: TEST 2: Wet Engine Compression Test.

CASE 3: The compression value of all 4 cylinders was similar and above 120 PSI. This is the correct and expected test result.