Here is a good method for checking compression.
With the engine removed, glow plug and flywheel installed,put a few drops of ARO in the exhaust port and turn the engine over a few times. Then spin the flywheel till you feel the beginning of the compression stroke, hold the engine by the flywheel with the cooling head 90 degrees (perpendicular) to the ground, time how long it takes for the weight of the engine to turn through the compression stroke and the cooling head is pointing at the ground.
Anything less than 10 seconds for this to occur means your engine is on its way out.

This is a much more comprehensive method of checking the overall compression than checking the engines pinch at TDC...some engines have a taper pinch while others use a straight pinch, engines with a straight pinch will feel like the pinch is gone while they still have good compression.