08-19-2013, 08:57 AM
What the others said. But I shall add this:
However you do the test, hot or cold, throttles open or shut, the readings should be consistent across all cylinders. Any individual number, because of a host of reasons, is meaningless. But the collective numbers, across cylinders and across time, have a great deal of meaning.
This I learned to my benefit when testing a V12 for sale. All cylinders measured equal until the last cylinder, which was crap. That last cylinder was just below the power brake booster port, and regardless of what you read elsewhere, power brake fluid is a _lousy_ lubricant. I got a good deal on the car because of the readings.
I fixed the leaky booster, and then got a consistent 150 psi, +/- a couple of psi, open throttle, on all cylinders. It was a small V12, so such high readings are to be expected.
Now to get to the bad news: a jumped timing belt or chain can give reasonably good numbers, yet the car will run like crap, if it runs at all. Compression checks, in isolation, are pretty much useless.
Eustace
However you do the test, hot or cold, throttles open or shut, the readings should be consistent across all cylinders. Any individual number, because of a host of reasons, is meaningless. But the collective numbers, across cylinders and across time, have a great deal of meaning.
This I learned to my benefit when testing a V12 for sale. All cylinders measured equal until the last cylinder, which was crap. That last cylinder was just below the power brake booster port, and regardless of what you read elsewhere, power brake fluid is a _lousy_ lubricant. I got a good deal on the car because of the readings.
I fixed the leaky booster, and then got a consistent 150 psi, +/- a couple of psi, open throttle, on all cylinders. It was a small V12, so such high readings are to be expected.
Now to get to the bad news: a jumped timing belt or chain can give reasonably good numbers, yet the car will run like crap, if it runs at all. Compression checks, in isolation, are pretty much useless.
Eustace