Old School Testing Tool

[Trav]

What would you think of a tool that cost $20-30 and could diagnose many engine problems including, low compression, bad rings, burned and sticking valve(s), bad valve guides, bad cat or exhaust restriction, restricted intake and a host of other common issues. A tool small enough to take with you when looking at a used car and quick enough to use to get a good idea on the general health of the engine?

I made a post bout this tool in clinebargers thread and decided it deserved a thread of its own. When I first started which was decades before the ECM or OBD we had points condenser, rotor and wires and the primary diagnostic tools were a tach/dwell, timing light, multi meter, compression tester and vacuum gauge, if you worked in a shop they may have had a scope.

The one tool that has been for the most part ignored today is the vacuum gauge, this is one tool that I would really miss if I didn't have one. The first time I saw one of these was in a early 60's car and it was labeled economy meter, the trick was for the driver to keep it as close as possible in the green area.
Even in trade school in the early 70's they mostly brushed past the usefulness of this tool.

The gauge is largely associated with carburetor engines but it works equally as well on FI as long as you can find full manifold vacuum somewhere, you can T in in you have to. It does not work on diesel engines as they produce very little vacuum but it can be used to diagnose the vacuum pump commonly found on them. Large cam engines may have lower vacuum levels but needle reactions will be the same.

I did a VW with flashing CEL and no power, suspected bad cat right of the bat, sure enough the vacuum gauge showed it right away, further testing confirmed high back pressure, off with the cat and surprise nothing in it. It had broken up and filled the muffler inlet. The vacuum gauge diagnosed this in seconds with no parts removal or wrenching.

This is a good site to see how one works and the amazon link is a OTC gauge for under $30

http://www.secondchancegarage.com/public/186.cfm

OTC gauge

 

[demarpaint]

Basic yet extremely valuable!

 

[Silk]

I keep trying to get the young guys at work to use one as the first step in diagnosis, but they don't have a clue what it is....and why I want them to use it. You need to understand how an engine works to know what the vacuum gauge is telling you...they don't, they want the scanner to tell them what's wrong.

The Holden Commodore 4 cyl we got in the early '80's had a vacuum gauge the size of a tach (it was the tach in the 6 cyl), and was marked out as an economy gauge.

 

[Kruse]

Originally Posted by Trav
The first time I saw one of these was in a early 60's car and it was labeled economy meter, the trick was for the driver to keep it as close as possible in the green area.
Even in trade school in the early 70's they mostly brushed past the usefulness of this tool.


My uncle used to have a Ford pickup that had a factory vacuum gauge on it. I think it was labeled as an economy meter or gauge or something like that. That was during the OPEC oil embargo era.
When I went to tech school, a vacuum gauge was on the "necessary" list of tools that we had to buy before classes started. I remember a classmate (who had obviously smoke too much weed in his youth) took a blow gun on his first day of class and pressurized the gauge. Of course, it didn't work after that and blamed Matco for giving him a defective gauge. Funny how mine worked for decades.....

 

[Snagglefoot]

Thanks for the post. I'm going to dig mine out and find a good vacuum source on each of my vehicles.

 

[spasm3]

I've had one for years. Handy tool.

 

[CT8]

I have had a couple over 50 years .

 

[Chris142]

My autoshop teacher in 10th grade spent most of the year showing us how to use one. I used one for years when I was working at shops that we're more geared towards engine work.

When my dad passed i inherited his made in USA craftsman one that as old as I am.

 

[Silk]

Calibrating a couple of mine.

 

[Kira]

As a payback I got good prices at an automotive tool place. It was a professional warehouse with "Fort Knox" security. The overall décor was dungeon and dark.

The guy brought me examples of the tools I mentioned AND A VACUUM GAUGE.


"You gotta have one of these", he said. I confess I haven't needed it not being a pro myself.

 

[spackard]

I'm having flashbacks to JC Whitney catalogs.

 

[JeffKeryk]

I adjust my carbs idle mixture with mine.
I have (at least) 2...
A friend had a huge older GMC dumper with an unknown small block Chevy.
Ran poorly and hard to start. Timing marks were impossible to find.
Set base timing for highest vacuum; dang thing ran strong!
Still no timing marks.

 

[HangFire]

The old one has been in the family for a while. Print it out and read it often; there's a whole automotive engine education on the dial.

Bought the new one only to get the + as well as the -. Old one still works great.

 

[Cdn17Sport6MT]

Is it just me?... but in the OP's post i can't open up the link and see the info re what particular vacuum gauge behaviour or readings actually mean.. I can open the link but there is no diagnostic interpretation info in there...?

 

[Silk]

Many years ago I read an old Sun manual that stressed the importance of a cold crank vacuum test before even starting a tune up. This became much more important in the '80's when we had a lot of gas (LPG and CNG) powered vehicles on the road...and I had a ticket in gas conversions. You wouldn't start a conversion or tune up without a cold crank vacuum test - on a petrol engine a couple of pumps on the throttle (with an accel pump) will put liquid fuel in the manifold, and there is some hope of starting. CNG is lighter than air, press the prime button and the gas goes up...no use there. LPG is heavier than air so will fall, not so bad. But you still need suck to get that fuel in. More subtle than a compression test, restoring vacuum is a test of skills.

 

[Trav]

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