Best place to place a vacuum gauge to get the best reading? 2H - 1979 HJ (1 Viewer)

[vincent85]

Hey guys,

Doing a full frame off I was doing allot of research and after reading a very compelling technical article on vacuum in the vehicle, I am going to add a vacuum gauge. I know we have a vacuum pump on the back of the alternator. Does this and the vacuum reservoir on the frame support function of anything beyond the brakes?

Here is a chart that I found as a excellent reference from that article that clearly shows the vacuum gauge being used (mainly in petrol engines), but still good technical data.

CONDITION INDICATION

Readings are at idle unless otherwise stated. Gauge readings are in inches

1. Normal Steady at 15 to 21; Drops to 2, then rises to 25 when throttle pedal is rapidly depressed then released.
2. Intake leak Low steady reading less than 10
3. Head gasket leak Gauge floats between 5 and 19
4. Improper idle mixture floats slowly plus or minus 1 ½ to 2 ½ inches
5. Small spark gap or defective points slight float plus or minus 1 to 1½ inches
6. Late ignition timing Approx 2 inches below normal idle
7. Late valve timing 4 to 8 inches below normal idle
8. Worn valve guides Oscillates plus or minus 2
9. Weak valve springs Violent oscillation (plus or minus 5 inches) as rpm increases. Often steady at idle.
10. Sticking valves Normally steady, will intermittently flick downward about 4 inches
11. Leaky valve Regular drop about 2 inches
12. Burned or warped valve Regular, evenly spaced down-scale flick approx 4 inches
13. Worn rings/ diluted oil Drops to 0, then rises to approx 18 when throttle is rapidly depressed then released
14. Restricted exhaust system Normal when first started. Drops to 0 as rpm increases. May eventually rise to approx 18

Any consideration or suggestions from experience where the best place to insert the mechanical sensor is?

Here is the autometer gauge: http://www.autometer.com/vacuum-4231.html

For everyones FYI here the article on vacuum: http://www.ih8mud.com/tech/vacuum.php

 

[whitey45]

Diesel engines dont produce vacuum like a gasser! Thats why they need a vacuum pump for the power brakes.

 

[duncanrm]

The most useful gauge I've added to a 2H is a Volt Meter.. much more useful than the Ammeter that comes from the factory..

 

[vincent85]

Whitey you know I actually knew diesels did not produce their own vacuum, but as you know our 2H in the diesel has the vacuum pump on the back of our alternator. I am still learning the finer details of the engine workings. So excuse my ignorance on some details. I just rebuilt most of my 2H, which was my first personal engine rebuild. So I am still learning and figuring details outs. I was mainly talking about putting in a vacuum gauge for the diesel application. I am just wondering it would be worth it or applicable at all to have the gauge in diesel application. So does the vacuum in a diesel only pertain to the braking system? I know we have a vacuum reservoir on the frame, is that all it is for?

I just thought it was handy to put in the 2 cents about the article which does mainly pertain to petrol engines and can be relative to everybody.

 

[vincent85]

The most useful gauge I've added to a 2H is a Volt Meter.. much more useful than the Ammeter that comes from the factory..

Why did you consider the volt meter better then the stock ammeter?

 

[duncanrm]

Why did you consider the volt meter better then the stock ammeter?

It doesnt cause fires for a start..

You can see at a glance if your alternator is charging, when the vehicle is ON but not started you can get an impression of your battery charge state, when you glow the plugs you can assess the health of your battery by the voltage drop you see..

 

[RufusTheDufus]

On your 2H the vacuum pump is only helpful for the brakes. Some later models used the vacuum switching valves to perform a number of functions like idle-up for air conditioning and triggering the shutdown function on the injection pump. Attaching that gauge to the vacuum system on your Troopy will only tell you if you have a leak.

It won't help at all for points 1-14 in the original post above. Why? On a petrol engine that gauge is connected to the intake manifold. It measures the vacuum inside the engine. The vacuum pump and plumbing on your 2H is completely external to the engine and isn't an indication of what might be happening inside the engine.

It's a waste of money. A volt meter is far more helpful.

 

[Henry James the 47th]

I couldn't add anything to Rufus's excellent advice - don't waste your money on a vacuum gauge.

 

[vincent85]

Great points everyone, thanks as usual. I am learning something everyday. I was not really considering a voltmeter, but after today I am going to add it for sure!

 

[vincent85]

I am going to get a mechanical voltmeter from autometer. They have two types one is 8-18V and the other is 16-36V. I think it is safe to assume that the 8-18V is the standard choice for my 12V vehicle application?

Have any of you wired a voltmeter into your Land Cruisers? Any tips or placements suggestions?

 

[Tapage]

After 18 years with my 2H gauges what I won't live without ..

1. Pyrometer

2. Oil Pressure

3. Water Temp

if you have turbo, obviously boost gauge.

 

[vincent85]

That is another one you hit the nail on the head with is the water temp. I got the EGT gauge, oil pressure, and boost thus far. I will be adding the voltmeter and water temp.

Thanks guys as always!

 

[vincent85]

Okay guys I wanted to elaborate and understand the vacuum process better myself regarding petrol vs diesel engines. We all know to this point that diesel engines do not produce vacuum naturally in the engine, as petrol engines do. I want to understand the process better and after doing some research this is one of the better explanations I found and it makes sense:


Vacuum is one of the major differences between gasoline and diesel engines. It's the chief reason diesels produce more MPG than gasoline engines.

Gas engines use a throttle blade to control air entry to the engine to control power output. Removing the throttle blade produces a runaway effect with a gas engine, wide open throttle as it were.

Diesels operate at WOT at all times. They require full cylinder filling with air to produce the heat necessary for compression ignition. Power on the diesel is managed by dispensing only the amount of fuel required at the time to meet the needs of the driver.

Having no throttle, there is nothing to restrict air intake to the engine. With no restriction, vacuum simply isn't built.

 

[RufusTheDufus]

That's a poor description of the purpose of the throttle plate. I wouldn't trust that source.

Diesel engines are much more efficient than gasoline because they run at a higher compression ratio. They convert more chemical energy into kinetic energy. By volume diesel #2 contains 13% more energy than gasoline. These two facts are the primary reason diesels produce higher MPG than petrol/gas. Vacuum or a throttle plate has nothing to do with it.

In order for gasoline to burn efficiently it requires the correct ratio of air to fuel at a given engine load. The throttle plate is a primary mechanical means to influence the proper ratio of air to fuel. (Lots of other things are involved in measuring the amount of air in the engine and metering the fuel to match the available air under the current driving conditions.)

The combustion processes of diesel and gasoline are very different chemical reactions. The ratio of air to fuel is important in a diesel though much less less critical than a gasoline engine. After ignition diesel will burn until all of the available oxygen is consumed or all of the available fuel is consumed.

Your 2H has a throttle plate. Based on your description it should be impossible for your engine to run at all because the cylinders cannot completely fill with air.

 

[rustybucket]

I would include on other item...water hight sensor, if it was possible to incorporate one. Last thing some one wants when off road, is a unknown water leak that drains your fluid with the risk of overheating the engine.

 

[vincent85]

That's a poor description of the purpose of the throttle plate. I wouldn't trust that source.

Diesel engines are much more efficient than gasoline because they run at a higher compression ratio. They convert more chemical energy into kinetic energy. By volume diesel #2 contains 13% more energy than gasoline. These two facts are the primary reason diesels produce higher MPG than petrol/gas. Vacuum or a throttle plate has nothing to do with it.

In order for gasoline to burn efficiently it requires the correct ratio of air to fuel at a given engine load. The throttle plate is a primary mechanical means to influence the proper ratio of air to fuel. (Lots of other things are involved in measuring the amount of air in the engine and metering the fuel to match the available air under the current driving conditions.)

The combustion processes of diesel and gasoline are very different chemical reactions. The ratio of air to fuel is important in a diesel though much less less critical than a gasoline engine. After ignition diesel will burn until all of the available oxygen is consumed or all of the available fuel is consumed.

Your 2H has a throttle plate. Based on your description it should be impossible for your engine to run at all because the cylinders cannot completely fill with air.

Yes you make a good point my 2H does indeed have a throttle plate. It has been very hard to find reliable information on this topic, I have seen various opinions. I will quote my source next time, but supposedly this person was a 30 year plus diesel mechanic. I knew already that diesels are more efficient than gasoline, because they run at higher compression ratios. I think the 2H runs at like 20:1, but I was not certain on how the vacuum worked exactly.

Thanks for correcting that information, the last thing I want is false information floating around. What you said makes allot more sense now that I think about it in contrast to what I have read.

 

[lostmarbles]

...Have any of you wired a voltmeter into your Land Cruisers? Any tips or placements suggestions?

I incorporated a voltmeter into the bracket I made for my diff-lock air pressure gauge and front/rear diff-lock switches and places that bracket just below the dash:

And here's where I got the feed for the voltage readout and the backlighting feed (to ensure the voltmeter is backlighted only when my sidelights (or sidelights+headlights) are on:

 

[Henry James the 47th]

Be careful. Tom is trying to lead you astray from LC purity with these aftermarket gauges. It's a slippery slope - soon you will have dozens of gauges, many of which will not even be hooked up...

 

[lostmarbles]

Be careful. Tom is trying to lead you astray from LC purity with these aftermarket gauges. It's a slippery slope - soon you will have dozens of gauges, many of which will not even be hooked up...

Yep.. The air gauge still isn't hooked up and I took those photos a long time ago too.......

(It's Xmas day already here Chris .....And I've consumed so much wine already that I can't even find the right smilie to add to this post err... and I've just knocked my precious glass over while typing away on this keyboard too. Amazing it still works! Must go for a refill....)

Edit: Actually what-da-ya-know....wine makes a good cleaner.... Underneath the printer hasn't been so clean in years.... Nice smell too...

Edit edirt... And the rest of the family here (why BTW are adults) are presently fighting over who's-is-who's with the little plastic toys they got in their Xmas crackers...

 

[Henry James the 47th]

Just trying, uh, to gauge your reaction, you know....