Turn the flywheel by hand, if its easy to turn then it has no or low compression, if its hard then its has good compression. Do this with the glow plug on tight.

The blue wire plugs into the part of the glow plug that sticks out, there is another wire from the ez start that goes into the engine body, (I think this is white & its sheilded). When testing if the ez start give power to the glow plug igniter (blue wire) remove the glow plug but keep the blue wire plugged into it, just touch the side if it to the engine block or cooling head to make a negative ground contact then activate the ez start to see if the glow plug lights up.