How To Test The Engine Compression (1.6L Suzuki Sidekick, Geo Tracker)

Testing the engine compression on your Suzuki Sidekick's (or Geo/Chevy Tracker's) 1.6L 4 cylinder engine is pretty easy.

In this tutorial, I'll show you how to do and interpret the results of your 'Dry' and 'Wet' engine compression test results.

Important Tips And Suggestions

TIP 1: If your 1.6L Sidekick's engine starts and runs, it's a good idea to let it warm up for about 15 minutes (before starting the compression test). I want to emphasize the key words: 'slightly warmed up engine' since it should not be hot.

Why warm up the engine? Because a slightly warmed up engine will improve the accuracy of your compression test results.

TIP 2: Take all necessary safety precautions as you work around a cranking engine. Use common sense and think safety all of the time.

TIP 3: The cylinder head, on your Suzuki, is made of aluminum so you should never remove the spark plugs if the engine is hot (hot = normal operating temperature). Removing the spark plugs from a hot engine can/will damage the spark plug hole threads in the aluminum cylinder head.

Symptoms Of Low Or No Cylinder Compression

Engine compression problems fall into 2 basic categories: Low engine compression in one or two cylinders and no compression in all cylinders.

When your Sidekick (Tracker) suffers from low engine compression, the engine will run but run rough and/or misfire.

When your Sidekick's engine has no compression in all cylinders, the engine will 'crank but not start'.

Here are some other specific symptoms you may see with low cylinder compression:

• If OBD II equipped, you'll have one or more of the following misfire diagnostic trouble codes: P0300, P0301, P0302, P0303, P0304.
• Engine cranks but does not start (0 compression in all cylinders).
• Blue smoke coming out of the tailpipe.
• Rough idle (engine misfires).
• Bad gas mileage.
• Engine 'misses' at idle but 'miss' disappears as you accelerate.
• Check engine light is illuminated with a MAP sensor trouble code (even tho' the MAP sensor is good).

With this info under our belts, let's head down to the next subheading and get testing.

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 some recommendations to you:

TEST 1: Dry Compression Test

You'll need to remove the spark plugs for the engine compression test and this will afford you the chance to see if the spark plug wire boots and spark plugs are swimming in motor oil (from leaking valve cover gaskets).

Leaking valve cover gaskets that are letting the spark plug tubes fill up with motor oil are a very common problem on the 1.6L engines. This problem will eventually result in a misfire condition as the oil cooks and creates carbon tracks on the spark plug or spark plug boot.

So, if you do spot a spark plug wire boot covered/dripping in oil, then you've found a the potential problem behind the misfire you're trying to diagnose with the compression test (you should still proceed with the compression test though).

OK, to get started this is what you'll need to do:

1. 1

   Disable the ignition system by disconnecting the ignition distributor from its electrical connector.
   
   This will prevent the ignition coil from sparking during the test.

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 plugs 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

   Now, record on paper 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 test the cylinder's compression one more time.

7. 7

   Repeat this test step on the remaining 3 cylinders.

Let's take a look at what your test results mean:

CASE 1: Low or no compression in 2 or all 4 cylinders. This test result indicates a serious internal problem.

The most common issues would be:

• Blown head gasket.
  • To further test this, I recommend the following tutorial: How To Test For A Blown Head Gasket (1.6L Suzuki Sidekick, Geo Tracker).
• Broken timing belt.
• Engine threw a rod.

CASE 2: Low compression in one or more cylinders. To a certain point, it's normal for the compression to vary a little between cylinders (as the engine accumulates thousands of miles).

But if these values vary too much, then you're gonna' have a bonafide misfire on your hands.

The next step is to do some math to find out if this low compression value is within a normal parameter or not. Go to: Interpreting Your Compression Test Results.

Interpreting Your Compression Test Results

If you're reading this section, more than likely your engine compression test results indicate you've got one or more cylinders with a low compression value.

Up to a certain range, a low compression value will not cause a problem. It's when the value is too low that you'll have a rough idle or a misfire condition on your hands.

To find out if the low compression value is causing a problem, you need to find out if it's lower than 15% of the highest compression value you got.

You can do this (figuring out the 15%) in one of two ways: You can calculate this 15% difference with pen and paper or you can use my low compression calculator. You can find the low compression calculator here: Online Low Engine Compression Calculator (at: easyautodiagnostics.com).

If you want to manually calculate the 15% difference, here's what you'll need to do:

• STEP 1: Multiply the highest compression value by 0.15 (this is the decimal value of 15%).
• STEP 2: Round the result to the nearest one (for example: 25.6 would become 26).
• STEP 3: Subtract the result (the number that was rounded) from the highest compression value.
• ANSWER: The result of this subtraction is the lowest possible compression value any cylinder can have.

Now, let me give you a more specific example: Let's say that I got the following compression readings:

Cylinder	Pressure
#1	165 PSI
#2	95 PSI
#3	155 PSI
#4	175 PSI

My next step is to do the following calculation:

• STEP 1:  175 x 0.15 = 26.25.
• STEP 2:  26.25 = 26 (rounded to nearest one).
• STEP 3:  175 - 26 = 149.
• ANSWER:  149 PSI. Any cylinder with this compression (or lower) value will misfire.

Since cylinder #2 is only producing 95 PSI, I can now conclude that it's 'dead' and causing a misfire.

To find out if the lowest compression value you got from your engine compression test is within a good range, you'll need to do the same calculation. Of course, you'll need to use the highest compression value you got and not the one in the example.

Once you've found the 'dead' cylinder, the next step is to find out what's causing the low compression value. For this step, go to: TEST 2: Wet Compression Test.

TEST 2: Wet Compression Test

If your 'Dry' compression test results indicate one or more cylinders with low or 0 compression, then the next step is to find out if that low compression value is due to worn/damaged cylinder head valves or worn/damaged piston rings.

To find out all we need to do is add a small amount of motor oil to the low compression cylinder and checking its compression once again. This is what is known as a 'Wet' compression test.

If the problem is bad piston rings, the motor oil that we're gonna' add will help bring the compression value up when we check that cylinder's compression again.

If the problem is bad cylinder head valves, the motor oil WILL NOT help raise the compression value of the cylinder. It's as simple as that!

OK, this is what you'll need to do:

1. 1

   Add a tablespoon (or two) of engine oil in the cylinder you need to retest.
   
   I suggest using a small and long funnel so that the oil will reach the inside of the cylinder.

2. 2

   Once you've added the oil, install the compression gauge, and as before just hand tighten it.

3. 3

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

4. 4

   You'll see one of two results:
   
   1.) The needle will climb higher than the previous compression number you recorded for this specific cylinder.
   
   2.) The needle will not move at all or stay at the same number you recorded earlier.
   
   What ever value your compression tester reads, write it down again.

5. 5

   Repeat steps 1 thru' 4 on any other cylinder that needs to be tested.

Let's take a look at what test results mean:

CASE 1: The compression value went up after adding motor oil and retesting. This tells you that the low compression problem is due to worn piston compression rings.

Here's why: The motor oil you just added helped the piston rings to create a tighter seal. With the piston rings now sealing the compression inside the cylinder, the compression value on your compression tester went up. This type of test result only happens when the problem is due to worn piston rings.

CASE 2: The compression value DID NOT go up after adding oil and retesting (in other words, it stayed the same). This result tells you that the low compression value registered in this cylinder (in the dry test) is due to worn/damaged cylinder head valves.