compression test

[guide002]

hello all, has anyone done a compression check with the vantage pro... wondering what your settings was.I'm using a 40 amp clamp...just not sure what the voltage scale should be.... it would be nice if they included it with the new update.....thanks

[leemack]

well i always thought you should use a high amps clamp as you'll be drawing around 200-400 amps.

But having said that i've seen video's on youtube were they use a lo-amps clamp.

[guide002]

yeah me too.. just not sure of the math side of it....

[hefaus]

Low Amp Probe Compression Test

Hi I had an old file I saved from a Forum Compression test. Hope this Helps with the settings. Have fun Keep Smiling.

[roadracer587]

As long as you are getting a waveform on the screen, it doesn't matter what scale you are on. Depending on your amp clamp setting, either on 10mv equals 1 amp or 100mv equals 1 amp will determine what your settings need to be to get a waveform. However, if you have a waveform, all you are looking for is a difference in current draw that would indicate a low compression cylinder. You will still not know what is causing the low compression and unless you are using another channel to trigger the scope you may not know which cylinder is the low one. Having said this, usually when you find a low compression cylinder it requires engine disassembly and it really does not matter which cylinder because you certainly would not redo the valves in one head only or replace the rings on one cylinder only. I use it just to be able to tell my customer that it will be rather expensive and will take a large amount of time. Hopefully this rant was helpful.

[guide002]

thanks guys that helps......

[protraxrptr17]

Use 40 amps AC coupled. I start with a 2 second sweep (may change it to make it clearer) If you have a low cylinder, pull a spark plug and look at the wave again. You will see a new dropout (unless you got lucky and pulled the one with low compression) which is the cylinder with the missing spark plug. Fill in the firing order and now you know which cylinder is low. Pull out your leakdown tester, and check it. Now you know which cylinder is weak and why.