how do I do a compression test?

[rculjak]

Hey guys, I was just wondering what the proper procedure was for a compression test, do all the plugs have to be out, the engine cant start so I am trying to see if I have good compression.

 

[88stangmangt]

do it plug by-plug and she will tell you all you need to know.

 

[rculjak]

do I leave the 7 plugs in and do the one cylinder, then put the plug back in and do the other cylinder always leaving the heads sealed?

 

[wisconsinboy]

yah usually you just go 1 by 1 all the way around and check for variences in the readings. i think you should ideally have it within 5% but i think goin up to even 10% isnt bad if its not in concurrent cylinders which would reveal you ahve a sealing problem somewhere in that area.

 

[wisconsinboy]

if you understand what im saying cause thats kinda confusing to me even.

 

[hllon4whls]

Take all plugs out. Srcrew compression testor in. Open throttle. Crank until needle stops climbing (or 3-4 revolutions). Record all cylinders. Find out if highest cylinder is with 10-15% of lowest cylinder. If it is you are good. If not, retest with some oil in the cylinder (about 1 teaspoon woth) if compression goes way up, then rings, if not possible head gasket or valve problem.

I assume you have trouble that you want to isolate?