Is Something Wrong With My Compression Tester?

[suth82 0]

Carried out a compression test yesterday but have a feeling that there is a problem with my gauge, when i crank the engine over the dial flickers up to about 200psi when on compression stroke but goes straight back down again, when you stop cranking the dial goes back down to zero.

 

Spent most of yesterday afternoon looking for a cause of poor compression but found nothing, iam now thinking that there is a problem with the gauge?? i presume there is supposed to be a non return valve so that pressure cannot escape from the gauge? Surely it should not go back down to zero after the dial going up to 200psi?

 

 

Paul

[Dan Ingram 1]

I cant speak for all compression testers but normally the gauge shouldn't drop down, it should work its way up to the highest compression. Mines digital so it works differently.

[welshpug 1,657]

surely if you're turning the engine over then you would lose the pressure as the exhaust valves open?! or do they have a valve in the tester?

[GLPoomobile 958]

My gauge has a non return valave, so once you've finished and taken the reading you press a button on the side and it releases the air and the gauge returns to zero.

 

If yours doesn't do that it must either be broken or it's a very cheap and nasty one.

[Rom 0]

Every tester i have ever used will keep pressure even after you stop cranking. Most will keep pressure till you release it, normally a button to press.

 

Ive seen tester go faulty, its certainly not unheard of. I wouldnt bother doing anything else until you either

 

a) get another tester to try

 

b.) try it on a known good engine

 

You could well be chasing ghosts if the gauge is duff

Edited April 27, 2008 by RKKRom

[suth82 0]

Ok thanks for the replies guys. I have now tested the compression tester by blowing compressed air into it and i could then hear the air leaking back out of the "non return valve". Its a Gunsun High gauge so if anyone is thinking of buying one then dont!!

 

Out to buy a better one tommorrow.

 

Paul

[Tom Fenton 1,542]

I've had a Gunson Hi Gauge for years, for the amount I use it, it does the job fine, sounds like you must have unfortunately got a duff one.

[jackherer 543]

I've had a Gunson Hi Gauge for years, for the amount I use it, it does the job fine, sounds like you must have unfortunately got a duff one.

 

 

Same here, but the first one I got was faulty so it is definitely worth swapping it, once you get one that works you should be fine.