‘Wet’ Engine Compression Test
Low (or no) engine compression in one or more (but not all) six cylinder on your 3.2L Isuzu is usually caused by worn cylinder head valves or worn piston rings.
The cool thing (if there's such a thing when testing for a worn out engine) is that we can find out without tearing down the engine. How? By doing a ‘wet’ compression test.
All that the wet compression test involves is adding about two tablespoons of oil to the engine cylinder that showed a low compression reading in the ‘dry’ compression test and testing its compression once again.
If the piston rings are worn, the engine oil that you just added will cause the compression value to shoot up to whatever the average compression value is for the rest of the cylinders.
If the cylinder head valves are worn (for that particular cylinder), the compression value will stay the same.
Here are the steps:
Add a small amount of engine oil to the cylinder that reported low compression or no compression in the ‘dry’ compression test. The amount should be about 1 to 2 tablespoons of oil.
Install the compression tester onto the cylinder.
Remember, do not use any type of tool to tightened the compression tester. Hand tight is fine.
Have a helper crank your Isuzu's engine after you've set up the test.
The compression test will either record a compression value that will go up (from the one you recorded before) or it will stay the same.
Let's interpret your test result:
CASE 1: The compression value shot up. This tells you that the piston compression rings are worn out and thus the problem is in the bottom end (block) of the engine in your 3.2L Isuzu Amigo (Rodeo, Trooper or 3.2L Honda Passport).
CASE 2: The compression value stayed the same. This confirms that the problem, causing the low (or no) compression value you recorded earlier, is in the cylinder head valves.
More specifically, you have burned out or broken cylinder head valves that are provoking the low (or no) engine compression condition in that specific engine cylinder.
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 in any auto parts store in any neighborhood, in any city, but you'll be paying at least twice as much. Go to the above compression tester links, browse and compare, you'll see a big price difference!
More Isuzu 3.2L Tutorials
You can find a complete list of tutorials in this index: Isuzu 3.2L Index Of Articles.
- How To Test The Isuzu 3.2L COP Ignition Coils.
- How To Test The Isuzu 3.2L Throttle Position Sensor.
- How To Test The Isuzu Manifold Absolute Pressure (MAP) Sensor.
- Ignition Control Module Test (1992-1995 3.2L Isuzu Rodeo and Trooper).
- How To Test The GM MAF Sensor (3.1L, 3.4L, 4.3L, 5.0L and 5.7L).
- For GM MAF sensor equipped 3.2L engines.
If this info really saved the day, buy me a beer!