On Mar 20, 6:38*pm, 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?

It's a percentage test with two gauges.

If you have cylinder(s) with major discrepancies you find out where
the air is leaking to.

If you hear air in the exhaust pipe it's a bad exhaust valve.

If you hear air in the intake it's a bad intake valve.

If you hear air in the crankcase (check where oil dipstick is) it's
bad piston rings.