I presume its a diesel tester you have, the compression ratio on your engine should be 19:1, if the readings through the pots are around that, you are ok
If they are down or erratic, that will diagnose which pot is at fault, after the initial test if some are down, try a squirt of engine oil in the bore and re test them, if the pressure goes up, its more than likely rings, if not it will probably mean a cylinder head problem
