This tutorial will help you step by step to perform an engine compression test on your 1.8L Nissan Sentra.
More importantly, I'll show you how to interpret your test results to determine if you actually have a problem or not.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Verificar La Compresión Del Motor (2000-2006 1.8L Nissan Sentra) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 1.8L Nissan Sentra: 2000, 2001, 2002, 2003, 2004, 2005, 2006.
Symptoms Of Low Or No Engine Compression
If the engine in your 1.8L Nissan Sentra does not have compression on all four cylinders, it will not start.
On the other hand, if a cylinder has low/no compression, the engine will start but will not idle smoothly.
Let me elaborate on both conditions:
Engine starts but runs with a misfire:
- Also known as an engine miss, rough idle condition. The usual causes are:
- Very low compression in one cylinder.
- Uneven engine compression that varies more than 15% across all 4 cylinders.
- Check Engine Light on with misfire codes:
- P0300 Random Cylinder Misfire.
- P0301 Cylinder #1 Misfire.
- P0302 Cylinder #2 Misfire.
- P0303 Cylinder #3 Misfire.
- P0304 Cylinder #4 Misfire.
- Bad gas mileage.
- This is caused by the simple fact that the engine is now running on 3 cylinders, making those 3 work harder to move the vehicle.
- Engine pollutes more.
- This is also simply because the engine is now running on 3 cylinders, which now have to compensate for the 'dead' cylinder.
Your Nissan won't start:
This is usually caused by 2 or all 4 cylinders not having compression. In this case, you'll see:
- The engine cranks very fast.
- This fast cranking speed is very noticeable.
- The ignition system is creating and delivering spark to all 4 cylinders.
- This tells you that the engine no-start problem is not caused by a fault in the ignition system.
- The fuel injectors spray fuel.
- You can confirm this with a Noid light test.
- You can also confirm this, albeit indirectly, by removing the spark plugs and checking to see if they're soaked with fuel (fuel fouled).
- Fuel pump is working and providing pressure.
- The most common causes of no compression on 2 or all 4 cylinders are:
- Blown head gasket.
- Broken timing belt.
- Engine threw a rod.
OK, now that we've covered the most common low and no compression scenarios, let's test if this is the case for your 1.8L Nissan vehicle.
Which Compression Tester Should I Buy?
There are many engine compression testers to choose from and many places to buy them. I'll give you two recommendations:
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.
2) Where To Buy: You can buy an engine compression tester almost anywhere, but you'll end up paying more for it (especially at your local auto parts store). The links above will help you comparison shop. I think you'll agree that this is the better way to save money on a compression tester!
TEST 1: 'Dry' Engine Compression Test
If you don't have an engine compression tester, you can buy one from your local auto parts store or, if you have an AutoZone or O'Reilly Auto Parts nearby, rent one there (they'll loan it for free after depositing a cash deposit for the tool, which you get back when you return it).
If you need help deciding where to buy one or which one, take a look at my recommendations: Which Compression Tester Should I Buy?
IMPORTANT: You'll be working near a cranking engine so be careful and stay alert at all times. Always think safety!
This is what you'll need to do:
- 1
Disconnect all of the fuel injectors. This will prevent fuel from being injected into the cylinders as you crank the engine.
- 2
Remove all four Coil-On-Plug (COP) ignition coils.
- 3
Remove all four spark plugs.
NOTE: Be careful when removing them and don't drop any of them on the Ground, otherwise the ceramic insulator of the spark plug may break, which may result in misfire! - 4
Thread the engine compression gauge into the spark plug hole for the number 1 engine cylinder (this is the spark plug hole closest to the drive belt).
Hand tighten the compression gauge only! Do not use any type of tool to get it tight. - 5
When the tester is set up, ask your helper to crank the engine while you keep an eye on the compression gauge.
- 6
Once the needle on the gauge stops climbing, have your helper stop cranking the engine.
- 7
Write down the compression value on a piece of paper. Include the number of the cylinder this reading belongs to.
- 8
Now repeat steps 4 thru' 7 on the other 3 cylinders.
Let's take a look at what your test results mean:
CASE 1: 0 PSI 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 (Nissan 1.8L).
- Broken timing chain.
- Engine threw a rod.
CASE 2: Low compression in one or more cylinders. Depending on how low the compression value, it could be causing a problem or not.
We can easily find out, if the compression value is causing a problem or not, by doing some math. Go to: Interpreting Your Compression Test Results.
CASE 3: 0 PSI compression in one or more cylinders. The cylinder or cylinders with 0 PSI compression are considered 'dead' and are causing a misfire problem or a no-start problem.
The next step is to do a 'wet' compression test and find out if the problem is due to bad piston rings or bad cylinder head valves. Go to: TEST 2: 'Wet' Engine Compression Test.
