You can glean a lot of information from the results of an engine compression test. For example: If low compression in one or more cylinders is causing a misfire condition and code. It can also help you find out if a ‘no-start’ condition is due to a broken timing belt or internal engine damage.
In this tutorial I'll explain how the compression test is done and more importantly, how to interpret its results.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar La Compresión Del Motor (2.2L Toyota Camry) (at: autotecnico-online.com).
Important Tips And Suggestions
TIP 1: If your 2.2L Toyota's engine starts and runs, let it warm up for about 15 minutes before you start your compression test. Don't let the engine reach normal operating temperature. The idea here is for your Toyota's engine to be ‘slightly warmed up’, 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. Please use common sense and think safety all of the time.
TIP 3: The cylinder head, on your 2.2L Toyota, 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 usually fall into 2 specific categories. These are.
- Compression problem causing a rough idle (misfire) when the engine is operating.
- Compression problem causing the engine to NOT start.
Let's go into a more detailed look at these two types of problems:
Low compression on one or two cylinders in your engine 2.2L Toyota Camry (Celica, or MR2) will cause the engine to misfire (shake) at idle. This misfire usually goes away once you accelerate the engine.
On OBD II equipped 2.2L Toyota's the PCM will set one or more of the following misfire codes:
- P0300: Random Cylinder Misfire.
- P0301: Cylinder #1 Misfire.
- P0302: Cylinder #2 Misfire.
- P0303: Cylinder #3 Misfire.
- P0304: Cylinder #4 Misfire.
Unfortunately, even if your Toyota is equipped with OBD II the computer doesn't always register a misfire trouble code even when the engine is experiencing a cylinder failure.
Zero compression in two or more cylinders will cause your 2.2L Toyota Camry (Celica, MR2) to ‘crank but not start’. Generally, when all 4 cylinders have no compression, you'll also see:
- Your 2.2L engine cranks very fast when trying to start it. This fast cranking speed is so noticeable that you know without a doubt that something's wrong.
- All 4 cylinders are getting spark. This let's you know that the engine's ‘cranks but does not start’ problem is not due to a fault in the ignition system.
- The fuel injectors are injecting fuel.
- You can confirm this by checking the injector pulse with a Noid light.
- You can confirm this by removing the spark plugs and verifying that they're soaked in gasoline.
The most common causes of zero compression in all cylinders are:
- Blown head gasket.
- Broken timing belt.
- Engine threw a rod.
Let's 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 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.
Engine Compression Gauge Testers
2) Where to buy: You can buy an engine compression tester just about anywhere, but you'll end up paying more for it (especially at your local auto parts store). The above links will help you comparison shop. I think you'll agree it's the better way to save money on the compression tester!
TEST 1: Dry Compression Test
OK, in this tutorial you'll be doing two types of compression tests. The first is a dry compression test and the second one is a wet compression test. The difference between them is that the wet compression test is done with a little bit of oil added to the cylinder that has low compression.
The purpose of the dry compression test is to find out the compression values of all 4 cylinders. If your Toyota doesn't start, then these values will tell you if the engine compression is behind the ‘no-start’ condition. If your Toyota is misfiring, then these values will let us know if there's cylinder with too low compression that's causing the misfire problem.
CAUTION: Be careful and be alert at all times since you'll be working around a cranking engine.
NOTE: If your Toyota's engine is hot, wait for it to cool down before removing 4 spark plugs. Removing the spark plugs from a hot engine can damage the spark plug threads in the cylinder head.
Alright, these are the test steps:
Disable the ignition system by disconnecting the ignition distributor from its electrical connector. This will prevent the ignition coil from sparking during the test.
Remove the spark plugs from a slightly warmed up engine (if it starts and runs). 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.
If the engine does not start, don't worry about it being warmed up.
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.
Have your helper crank the engine till the needle on the compression gauge stops climbing.
Now, record on paper the value at which the needle stopped and the number of the engine cylinder on a piece of paper. Release the pressure on the gauge and repeat this step one more time.
Repeat this test step on the remaining 3 cylinders.
Let's take a look at what your test results mean:
CASE 1: You go 0 PSI compression on all 4 cylinders. This is not good and tells you that one of the following conditions exists
- Timing belt problem.
- Blown head gasket.
- Blown engine.
Any compression value below 100 PSI (even if it does not 0 PSI) means internal mechanical engine trouble.
CASE 2: Some, but not all, of the cylinders had a low compression value. Up to a certain point this is normal -especially if the engine has a lot of miles.
What is NOT normal is if the values vary too much. With a bit of math we can find out if the lowest compression values are normal or not. Go to: Interpreting Your Compression Test Results.
The rule of thumb is that the lowest compression value cannot vary more than 15% from the highest value you recorded. Any cylinder with a compression value lower than 15% of the highest will misfire.