Leak down tester

Sounds like dud chinese gauges perhaps.  Imagine how it works - there's a driving pressure P1 and a calibrated leak across a small orifice, giving you a pressure in the second part of the instrument / cylinder P2.  If leakage = 0 then P2 = P1 and you have zero leakdown.  If leakage is infinite, P2 = 0 and you have 100% leakage.
The flow across the orifice should be more or less matched to the cylinder leakage at the driving pressure (eg 60psi) to give it sensible reading on the second gauge.
I would take both gauges off and put them on a common manifold and see if they read the same.  Also check orifice between the two chambers, it is usually somewhere around 1mm. 
Your instrument had a schraeder valve added to the nozzle so who knows what they were on when they made it! :)

I could not get any sensible results out of mine till I replaced both gauges and the reg with decent quality ones from SMC.
 
The hose to connect to the spark plug hole should not be connected to the gauges when you set the pressure. Set the pressure on the gauges THEN connect the hose. See the "how to use"youtube vid I posted earlier this thread and better still the second vid showing how to convert the tool so it testes at 100psi.
 
breganzane said:
Sounds like dud chinese gauges perhaps.  Imagine how it works - there's a driving pressure P1 and a calibrated leak across a small orifice, giving you a pressure in the second part of the instrument / cylinder P2.  ...
... I would take both gauges off and put them on a common manifold and see if they read the same.  Also check orifice between the two chambers, it is usually somewhere around 1mm. 
Click to expand...

Yes, I'd figured out the basic workings of the thing and come to the conclusion that it's fucked.

Probably not easy to compare the gauges directly because they're calibrated differently. One is PSI and the other is %. The % gauge is very sensitive, a couple of psi is enough to send it off scale.

I reckon I'll just put this in the "you get what you pay for" category. Was worth a try, but turned out to be a miserable failure. If anyone else is considering purchasing one of these cheapo things, save your money. Or rather, spend a bit more on a decent instrument.


Davo said:
The hose to connect to the spark plug hole should not be connected to the gauges when you set the pressure. Set the pressure on the gauges THEN connect the hose. See the "how to use"youtube vid I posted earlier this thread and better still the second vid showing how to convert the tool so it testes at 100psi.
Click to expand...

The order of connections makes no difference. The stupid thing doesn't work either way. Only difference is that the coupling between the spark plug hose and the instrument is a normal compressed air hose fitting - has a valve in it, so when disconnected there's no flow.
 
Dellortoman said:
Yes, I'd figured out the basic workings of the thing and come to the conclusion that it's fucked.
Probably not easy to compare the gauges directly because they're calibrated differently. One is PSI and the other is %. The % gauge is very sensitive, a couple of psi is enough to send it off scale.
I reckon I'll just put this in the "you get what you pay for" category. Was worth a try, but turned out to be a miserable failure. If anyone else is considering purchasing one of these cheapo things, save your money. Or rather, spend a bit more on a decent instrument.
Click to expand...

In fairness, this is exactly what I said would happen.  :)

However...

When leakage = 0 then P1=P2, gauges are reading the same pressure.  Hence I figured they should be perfectly OK being the same gauge, so I just fitted 2x identical SMC 1/8 BSP gauges to my chinese tester.  I set P1 to be say 80PSI and I get for example 70psi on the 2nd gauge, = 12% leakdown.  These things are not a calibrated instrument anyhow, they offer comparative readings.  So I tested mine on a few known decent engines to get a bit of a baseline.  I certainly got a result when I bent a valve, big fat zero psi on G2! :)

The tester itself is just a convenient bit of plumbing with an orifice between the two gauges, nothing more.  With decent pneumatic parts it will work fine.  But I agree it is a good example of a chinese knock off tool that is totally useless as delivered.
 
breganzane said:
In fairness, this is exactly what I said would happen.  :)
Click to expand...

Nobody likes a smart arse  :D

Fucking piece of crap leak down tester. I?m now looking for suitable pressure gauges to try to make it work. But I have this sinking feeling that I?m just chucking good money after bad.

I'll probably end up spending more than a decent leak down tester would have cost in the first place, and end up with a mediocre result  ::)
 
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