- #1
zoobyshoe
- 6,510
- 1,290
I've never done this before, and undertook it for the first time today, guided by books, google, and YouTube.
My truck's a 4 cylinder. I did the first test after driving it for a while to warm it up. I got 150-150-146-140 psi for the four respective cylinders 1-2-3-4. The instruction I was following was to crank the engine for about 5 seconds on each cylinder.
After reading some more, I found a site that said you should only crank 6 revolutions per cylinder. Otherwise you can falsely build up acceptable pressure in a cylinder that might actually be worn or have worn valves. So, I redid the test, trying to count 6 revolutions by ear.
This time I got 120 plus or minus 2 psi on all four cylinders. However, the 6 revolutions seemed to me to take about the same time as my previous 5 second count. The difference may well have been due to an hour of cooling off time: I didn't warm the engine up before the second test.
Anyway, my real question is about acceptable readings. I have two separate manuals for the car, one Chilton's, one Haynes, and neither says what acceptable readings are supposed to be. (I checked them both over for a long time.) Both books explain how to do a compression test, but neither tells you what the readings you get may mean.
A website I found says anything above 100 psi is acceptable. 135 or more would be considered excellent. The implication was that this is true of all cars. Is that the case?
My truck's a 4 cylinder. I did the first test after driving it for a while to warm it up. I got 150-150-146-140 psi for the four respective cylinders 1-2-3-4. The instruction I was following was to crank the engine for about 5 seconds on each cylinder.
After reading some more, I found a site that said you should only crank 6 revolutions per cylinder. Otherwise you can falsely build up acceptable pressure in a cylinder that might actually be worn or have worn valves. So, I redid the test, trying to count 6 revolutions by ear.
This time I got 120 plus or minus 2 psi on all four cylinders. However, the 6 revolutions seemed to me to take about the same time as my previous 5 second count. The difference may well have been due to an hour of cooling off time: I didn't warm the engine up before the second test.
Anyway, my real question is about acceptable readings. I have two separate manuals for the car, one Chilton's, one Haynes, and neither says what acceptable readings are supposed to be. (I checked them both over for a long time.) Both books explain how to do a compression test, but neither tells you what the readings you get may mean.
A website I found says anything above 100 psi is acceptable. 135 or more would be considered excellent. The implication was that this is true of all cars. Is that the case?