In this tutorial, I'll explain how to test the engine compression on Nissan vehicles with a 1.6L 4-cylinder engine. More importantly, I'll explain how to interpret the test results so that you can know whether you have a bad cylinder or not.
The engine compression test is easy and fast especially so because the 1.6L engine's spark plugs are very accessible and can be removed without much effort.
Contents of this tutorial at a quick glance:
- Important Tips And Suggestions.
- Symptoms of Low or No Cylinder Compression.
- TEST 1: Dry Compression Test.
- TEST 2: Wet Compression Test.
- Which Compression Tester Should I Buy?
Puedes encontrar este tutorial en Español aquí: Cómo Verificar La Compresión del Motor (1.6L Nissan) (en: autotecnico-online.com).
Important Tips And Suggestions
TIP 1: If your 1.6L Nissan'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. Your safety is your responsibility... so use common sense and think safety all of the time.
TIP 3: The cylinder head, on your Nissan, 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
Generally, compression problems can be divided into two categories:
- Low compression in one or more cylinders causing a rough idle (misfire) when the engine is operating.
- Zero compression on all cylinders causing the engine to crank but 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 1.6L Nissan will cause the engine to misfire at idle. This misfire usually goes away when you accelerate the engine.
If your Nissan is OBD II diagnostic system equipped, you'll also see one or more of the following misfire trouble 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 Nissan is equipped with OBD II... the computer doesn't always register a misfire fault code even when the engine is truly experiencing a cylinder failure.
Zero compression in two or more cylinders will cause your 1.6L Nissan to ‘crank but not start’. Generally, this usually happens when the head gasket is blown or there's a timing belt/chain issue.
You'll also see one or more of the following symptoms:
- When you crank the engine to start it, it cranks very fast and this fast cranking speed is so noticeable that you know without a doubt that something's wrong.
- Each cylinder is 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...
TEST 1: Dry Compression Test
You need to remove the spark plugs to perform compression test. I suggest you mark the spark plug wires before removing them so that you can install without complications/headaches when you complete the test.
CAUTION: Be careful and be alert at all times since you'll be working around a cranking engine.
NOTE: If your Nissan'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: If the engine does not start and the results of the engine compression test are 0 PSI on all 4 cylinders then you have one of the following conditions:
- 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: If the engine does start, the very first thing you'll notice is that the compression values you wrote down for each cylinder are slightly different from one another. This is normal.
What is NOT normal is if the values vary too much. The cool thing is that we can find out if the variations in the values, you wrote down, indicate a problem (with that cylinder) or not.
The rule of thumb is that they can not vary more than 15% from each other and if they do... you're gonna' have a genuine misfire condition on your hands or possibly a No Start Condition (if more than one cylinder is affected).
How do you figure this out?... This is how you do it:
- Grab a calculator and multiply the highest compression reading that you recorded by .15. So, let's say that cylinder #4 gave you the highest reading of 170 PSI. Well 170 X .15 gives you 26 (25.5 rounded off).
- Now, the next step is to subtract 26 from 170... which gives us 144 PSI.
- So then, 144 PSI is the lowest possible compression reading that any one of the rest of the engine cylinders can have. Any compression reading below this.. and that engine cylinder will misfire.
To make better sense of the above calculation... let's say that my 1.6L Nissan produced the following compression test results:
- Cylinder #1 175 PSI.
- Cylinder #2 165 PSI.
- Cylinder #3 160 PSI.
- Cylinder #4 110 PSI.
The next step is to do the math: 175 x .15= 26, 175-26= 149. So, now I know that cylinder #4 is the one causing the misfire!!