no compression is:

either a hole in your piston ( no compression)
knackered piston rings ( very little or no compression)
bent or damged valves ( no compression)
cracked cylinder head( u would get a little compression)
cracked bore wall ( u would get a little compression)
headgasket( u would get small compression)


doubt its the plugs unless its not seated right but u would hear it pop as the pressure would be good!