TEST 2: Wet Compression Test
The very last step, if you have one or more cylinders that have very low compression values, is to do a wet compression test on those specific cylinders.
This type of test will help you find out if the low compression value is due to worn valves in the cylinder head or worn rings on the pistons.
This involves adding a spoonful of engine oil to the affected cylinder and testing the compression again.
OK, this is what you'll need to do:
- 1
Add a tablespoon 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
Once you've added the oil, install the compression gauge, and as before just hand tighten it.
- 3
Now, have your helper crank the engine till the needle stops climbing on the compression gauge.
- 4
As before, your job is to keep an eye on the gauge, and 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
If you have another cylinder that needs to be tested then repeat steps 1 thru' 4 on it now.
Let's take a look at what your compression test results mean:
CASE 1: The needle on the gauge registered a higher value. This tells you that the lack of compression (or low compression) recorded earlier is due to bad or severely worn piston rings.
CASE 2: The needle DID NOT move beyond the previous recorded value. This result tells you that the problem is due to worn intake or exhaust valves in the cylinder head.
Related Test Articles
To see all of the 2.6L Isuzu specific articles here at troubleshootmyvehicle.com, go to: Isuzu 2.6L Index Of Articles.
Here's a sample of the articles, you'll find in the Index of Articles:
- 2.6L Isuzu MAF Sensor Test Amigo, Pick Up, Rodeo (1993-96).
- Blown Head Gasket Test Amigo, Pick Up, Rodeo (1993-96 Isuzu 2.6L).
- How To Test The Fuel Injectors (2.6L Isuzu Pick Up).
- Testing A Bad Alternator: Symptoms And Diagnosis.
- How To Bench Test The Starter Motor.
If this info saved the day, buy me a beer!
