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John

Ed Huntress wrote:
On Wed, 20 Mar 2013 21:56:51 -0400, wrote:

On Wed, 20 Mar 2013 21:38:05 -0400, Ed Huntress
wrote:

On Wed, 20 Mar 2013 18:24:12 -0700 (PDT), jon_banquer
wrote:

On Mar 20, 6:04 pm, Ed Huntress
wrote:
On Wed, 20 Mar 2013 19:59:49 -0400,
wrote:
On Wed, 20 Mar 2013 11:49:22 -0400, Ed Huntress
wrote:

On Wed, 20 Mar 2013 08:42:16 -0700, "PrecisionmachinisT"
wrote:

"Ken Grunke" wrote in message
...

I am assuming there has to be a separate check valve INLINE between the
plug adapter and the gauge below the release valve.
That is what I am missing. It may be a fitting I had,
but absent-mindedly misplaced.

Could be a spring and or check ball is missng or gunked
up at the spark plug fitting end...

--FWIW blowing into the end with your mouth probably
won't produce enough hose expansion to actuate a ball
type check valve.

Sorry for jumping into the middle without having read the
thread, but there are two kinds of compression testers:
the regular kind, which have a button to activate the
check-release valve; and leak-down testers, which have no
such valve.

I have both. They look almost the same. Perhaps, if Ken's
tester doesn't have a check valve, he has a leakdown
tester. If so, it will have a spark-plug-thread terminal
end. Regular testers *may* have such a thread. Mine just
has a tapered rubber plug.
A leakdown tester should have 2 guages and WILL have a
connector for compressed air.

Mine has one gauge. It's around 45 years old. And as I noted
in an addition to the post above, it has a Schrader valve for
pumping up the cylinder.

What's the second gauge for? With mine, you just attach it,
make sure both valves are closed, and pump it up. Test dry,
then test wet (with about an ounce of oil in the cylinder;
more for a V-engine).

Is there something else that I've missed?

-- Ed Huntress

One gauge tells you your air input pressure, the other your
cylinder pressure.

I don't understand that. All you care about is the air you get
into the cylinder, right?

I used to do a lot of leakdown tests, and I think I remember how
they were done. All I did was pump the cylinder up to some
pressure and time how long it takes to drop to some lower
pressure. Do the test dry, then wet, in each cylinder. If it
falls faster when dry, it's rings. If it's the same time when
wet, it's valves.

Am I missing something?
I guess you can do it that way, but it's not terribly effective or
accurate. A normal leakdown tester feeds 80psi to one side of a
restriction, which feeds the air into the cyl. Guage on inlet
(generally 80 psi) and on the cyl side. With no leakage at all you
get 80/80. If you have a small leakdown (normal) you may have
80/75. A sognificant leak may give you 80/60 or 80/50.

Then you listen in the intake, exhaust, and crankcase to tell
where the air is going.

Yeah, I can see that it's very quick to diagnose several problems.
But watch out what you call "normal." g Unless I'm mistaken, those
two-gauge deals didn't exist when I was club racing, in the late
'60s and early '70s. At least, it wasn't equipment that we
bottom-dollar sports car types had. The ones we used were "normal"
then.

I do see a limitiation of this newer device, compared to the old
ones, however. I described it in one of my posts to Jon.

The leakdown testers were used in aviation. The calibrated leak in the
tester has a spec. for hole size and length as well as other
dimensions. There are more than one size of calibrated leak. For
larger cylinders such as a 200 Cu In on a 1820 Wright you had to use a
larger calibrated leak gauge or every reading would indicate a bad cylinder.

http://en.wikipedia.org/wiki/Leak-down_tester

John