Greenie Posted September 6, 2012 Share Posted September 6, 2012 Hello,I'm thinking of buying a compression tester but wouldn't use it very often, are the cheapy ones any good for a skinflint infrequent user?Something like this...http://www.ebay.co.uk/itm/PETROL-ENGINE-AUTOMOTIVE-COMPRESSION-TESTER-TOOL-KIT-/400303386303?pt=UK_Diagnostic_Tools_Equipment&hash=item5d33f0eebf Quote Link to comment Share on other sites More sharing options...
herald948 Posted September 6, 2012 Share Posted September 6, 2012 That should be fine; in fact, I have one very similar to it, and it seems to work very well. Understand that you don't really need anything with accuracy down to 6-7 decimal points. Relative readings are fine, so if the gauge is actually off by several psi, it doesn't matter, as you're really comparing amongst all cylinders. In other words, that gauge might show readings of 130-125-128-130, while someone else's might show 135-130-133-135. No problem, unless you're dead-set on knowing the absolute correct number. ;) Quote Link to comment Share on other sites More sharing options...
thebrookster Posted September 6, 2012 Share Posted September 6, 2012 I use the Gunson Tester, available from Machine Mart etc.However, the thing to remember is to basically ignore the actual readings, OK it may well read in the ballpark area but these devices are not accurate!! For accuracy you pay a LOT more, and have to faff around calibrating the darn thing everytime you use it.What these testers are good for (and this is what most of us use them for) is showing variations between cylinders, and also showing dramatic loss of pressure in any/all cylinders.So when you look at it like that, basically all your tester needs is to have an easy to read dial, the correct fittings for your engine and be able to cope with the expected pressures (in particular hose fittings etc, the last you want is a cheap tool where the hose pings off in your face as you try to read guage!! 150-200 PSI will hurt!!)Cheers,Phil Quote Link to comment Share on other sites More sharing options...
Greenie Posted September 6, 2012 Author Share Posted September 6, 2012 Thanks Phil and Andy. Good advice about the hose potentially pinging off - I better get my nearest and dearest to read the dial in that case...CheersSimon Quote Link to comment Share on other sites More sharing options...
Sheepy Posted September 6, 2012 Share Posted September 6, 2012 Simon, Like the others say, that one should be good for what the average d.i.y'er needs.I have one similar that I had from a tenneager, and it's fine, I also have a top notch one, from an old company I worked for that folded.I once tested an engine with both gauges, and there was not a lot between them.Also, when you have her read the gauge for your safety, tell her it's because you can't read it and turn the motor over at same time! ;DGood luckShaun Quote Link to comment Share on other sites More sharing options...
Dannyb Posted September 6, 2012 Share Posted September 6, 2012 1936 wrote:Hello,I'm thinking of buying a compression tester but wouldn't use it very often, are the cheapy ones any good for a skinflint infrequent user?Something like this...http://www.ebay.co.uk/itm/PETROL-ENGINE-AUTOMOTIVE-COMPRESSION-TESTER-TOOL-KIT-/400303386303?pt=UK_Diagnostic_Tools_Equipment&hash=item5d33f0eebfI have the same one as that. Works a treat. I also found it fairly accurate when testing a motorbike with a known compression. Quote Link to comment Share on other sites More sharing options...
Greenie Posted September 6, 2012 Author Share Posted September 6, 2012 Thanks Dannyb and everyone, I've just ordered one - saw the same one even cheaper at £9.49, and I need to save all my pennies for Beaulieu this weekendShaun, I don't know if I'll get away with spinning her that line - I was all brave until the reality sank in of what would happen to me if she got a high pressure hose on the nose. Quote Link to comment Share on other sites More sharing options...
GT6 M Posted September 6, 2012 Share Posted September 6, 2012 its not just the figures you need to look at, but how the figures are gotlook at how far it jumps up in first strokes, a lang way, is good, then slightly less on other pumps,till its gone no further, generaly about 6-8 pumpsbut ,if its only very slow build up,and not much on first pump, then some thing amis.also try a running test, it shows just how well your engine is working at tick over.will be alot less than cranking test, by about 60-100 depending on cam.M Quote Link to comment Share on other sites More sharing options...
Greenie Posted September 9, 2012 Author Share Posted September 9, 2012 Thanks Marcus - I now have my engine running so will see how it looks when the tester arrives. Quote Link to comment Share on other sites More sharing options...
Mr Elsie Posted September 9, 2012 Share Posted September 9, 2012 Daft question... How do you use the compression testers. Do you connect and turn engine via cranking fan or do you turn it over via ignition? Quote Link to comment Share on other sites More sharing options...
Clive Posted September 9, 2012 Share Posted September 9, 2012 Wide open throttle, turn over on the starter. Turn over a few times and write down each compression. If something odd, add a teaspoon or 2 of oil to each cylinder in turn, and measure again. That will give a basic diagnostic of piston or valve leaks.Best to take all the plugs out first! (and label the plug leads) Quote Link to comment Share on other sites More sharing options...
Sheepy Posted September 9, 2012 Share Posted September 9, 2012 cliftyhanger wrote:Wide open throttle, turn over on the starter. Turn over a few times and write down each compression. If something odd, add a teaspoon or 2 of oil to each cylinder in turn, and measure again. That will give a basic diagnostic of piston or valve leaks.Best to take all the plugs out first! (and label the plug leads)Clive is correct, but just to add to it, disconect the H.T. Lead from the coil also.And I would turn over the engine, until the needle stops increasing on the gauge, (may be more than a few times) make sure your battery is charged! :)Some testers have a pressure release button on them, don't forget to release pressure before testing the next cylinder.Then write down your results comparing figures to manufacturers specs, and to the other cylinders. Quote Link to comment Share on other sites More sharing options...
drofgum Posted September 9, 2012 Share Posted September 9, 2012 Hi,One thing I do to make a more complete check of the readings is to repeat the first cylinder test after testing all other cylinders. This gives a second reading to show how much, if any, has been lost from the battery during the test. Occasionally it will show enough loss that when added to the last cylinder it is within a safe range of the highest cylinder where without this allowance it would indicate the need for more serious engine work. Cheers, Paul Quote Link to comment Share on other sites More sharing options...
thebrookster Posted September 9, 2012 Share Posted September 9, 2012 1317 wrote:Hi,One thing I do to make a more complete check of the readings is to repeat the first cylinder test after testing all other cylinders. This gives a second reading to show how much, if any, has been lost from the battery during the test. Occasionally it will show enough loss that when added to the last cylinder it is within a safe range of the highest cylinder where without this allowance it would indicate the need for more serious engine work. Cheers, PaulCrikey, I shall keep this tip in mind from now on!! A dull battery could make quite a difference when you think about it.Cheers for that Paul :)Phil Quote Link to comment Share on other sites More sharing options...
Docman Posted September 11, 2012 Share Posted September 11, 2012 Does the engine temperature matter? It's been a while but I think the engine should be up to temp as you would do when checking valve clearances, correct?.Again, I may be off base, it's been a while. I need to check both on mine. Quote Link to comment Share on other sites More sharing options...
thebrookster Posted September 11, 2012 Share Posted September 11, 2012 Yes, you do want the engine up to temperature IIRC!! Quote Link to comment Share on other sites More sharing options...
.thumb.jpeg.b15b81ef10abeea1c3039ae03c4a9f3a.jpeg)
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.