compression gauge puzzler

Not how it's supposed to work. Most of them use a check valve in the plug adapter fitting on the end of the hose. 99% use a tire valve core type valve. Looks just like the release valve in that T fitting on the old gauge.

Oh the old unit uses nothing more than a bog standard air pressure gauge with a "compression tester" face on it. The spark adapter fittings are the part that makes it special.

"Schrader"

If the check valve was further up the hose the dead space would lower the reading.

several years of non-use, it's demise helped along by a good dose of rust. I needed one for a project car I just started working on so I went ebay shopping for a replacement gauge to go on my hose & adapters.

with a release valve for a good price of $15 including shipping but there isn't a check valve to hold the pressure for cumulative readings. On my old gauge, it must be built into the gauge's body as I don't see any kind of external check valve on it.

cycle. I'm not familiar with how a standard automotive compression tester is supposed to work here, other than it should hold the pressure and increase the reading a bit with each crank cycle of the motor.

It jumps to 300 lbs on each crank and then drops off again?

The gauge is missing a check valve in the bottom of the hose above the spark plug adapter

The methodology of the left has always been:

1. Lie
2. Repeat the lie as many times as possible
3. Have as many people repeat the lie as often as possible
4. Eventually, the uninformed believe the lie
5. The lie will then be made into some form oflaw
6. Then everyone must conform to the lie

Perhaps Ken can rescue the adapters with check valves off the old gauge. The fittings are probably standard pipe thread with some Teflon tape.

My compression gauge has a two piece adapter. The adapter for larger spark plug threads can be unscrewed for the smaller plug sizes. Once this part is unscrewed, the tire valve type check valve is clearly visible and can be removed/replaced with a (cheap) special tool.

Yep, A Schrader type valve core. However some folks don't know that name.

I have units with the valve at the tip and one with the valve right at the gauge. No difference in the readings but they ones at the adapters are easier to change out.

ugh this Google Group thing is scary, I'll get me a *real* newsgroup reader ...

So I am missing the Schrader valve, I don't see it in the hose end where th e adapters screw on to, nor in the fitting at the gauge. So it's either in side the gauge or it's just plain lost. I haven't used the thing for eons, it sat on a shelf in the garage but I do remember it working back in the da y when I still had most of my hair and better eyesight. I did buy the thing new and used it a few times.

No Gunner it goes up to whatever that cylinder's pressure is, the four cyli nders varied between 150 and 200 on a 20 yr old engine.

Bingo, I had everything apart and do not see any check valve or schrader va lve.

Sure I'm trying to save a couple bucks, and also trying to avoid the Chines e crap that is rampant on ebay (and everywhere else). I live in the boonies and don't hit the metropolis very often. And yes, I am a penny pincher on a limited income.

Paul, I am using the adapters and hose from my old tester with the new gaug e in place of the rusty old one. Maybe at some point the check valve fell out when I was switching adapters? Dunno.

Guys, thanks for the replies, I'm gonna sleep on it and maybe look for anot her gauge on ebay in the morning. BTW the seller was a fabulous guy who off ered a full refund including shipping. I searched high and low for the box the gauge came in and told him I couldnt find it, expecting him to refuse t he refund. But he answered back don't even bother returning the unit, just use it for a paperweight and then he refunded the full amount. Now there's a nomination for ebay seller of the year :)

You might try putting some soapy water or spit around the fitting where the release button is, just below the gage to see if bubbles are present with some pressure applied. Then, if that release button assembly can be disassembled, you might find a fleck of dirt or possibly a missing ball or spring.

In the section where the button is, there should probably be a check valve which holds the pressure in the gage until the user presses the button.

There are also some types of compression testers which have the check/tire valve core located at the end of the tube where the rubber tip is (which is intended to seal in the spark plug hole.

But the release button on the Proto gage should engage something acting as a check valve.

Another less likely fault could be that there is an internal leak in the Proto gage, which is a little more complicated to check and repair, but possible.

Nope, it's just the release valve. That works fine. I can blow into the hos e with all my cheekmuscles, and the button will release the pressure - ther e is nothing between the gauge and the plug adapter, only a free passage. S ame with the old gauge, it has only the release valve. That one is a Schrad er valve in a T-fitting just below the gauge which is plainly seen in my fi rst picture:

I am assuming there has to be a separate check valve INLINE between the plu g 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.

Well, they do now...

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.

Whup, I hit "send" too fast. The leak-down tester also has a Schrader valve, for filling the cylinder with air.

Am I repeating stuff that's been said? If so, I apologize.

I am assuming there has to be a separate check valve INLINE between the

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.

John

with all my cheekmuscles, and the button will release the pressure - there is nothing between the gauge and the plug adapter, only a free passage. Same with the old gauge, it has only the release valve. That one is a Schrader valve in a T-fitting just below the gauge which is plainly seen in my first picture:

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.

Yes, and they usually fit into the line as you assumed. My old Snap-On has some at the air fitting end and some at the plug end. Look for internal threads at both ends of your adapter, Ken. The only thing which may be missing is a schrader valve insert.

with all my cheekmuscles, and the button will release the pressure - there is nothing between the gauge and the plug adapter, only a free passage. Same with the old gauge, it has only the release valve. That one is a Schrader valve in a T-fitting just below the gauge which is plainly seen in my first picture:

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. Is there an internal thread anywhere in the end of the hose/fitting? If so, pop a tire valve in and try it A tire valve may drop your pressure reading a bit more than the "proper" valve - some testers uses special valves, some used regular tire valves - some long - some short. Long will have less effect on the reading if it can be used (softer spring)

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?