I have a 1993 ford f150 with a 5.0 it developed a dead miss on one cylinder and has 0 compression on the cylinder....using the hose from the compression gauge I can not blow air into this cylinder but can suck air through it .....any ideas here?

I am by no means a mechanic but I have done a few rebuilds ...just dont understand what is causing this one intake valve stuck open maybe?It seems that since I can not blow air into the cylinder it is holding compression since it can be pressurized this way,so I assume it is not a burnt exhaust valve or air would just blow through with no resistance.Thge same I would assume of the compression rings if they hold pressure blown in through a line in the plug hole then they would not cause 0 compression ? right?

A vacume applied acts as if its wide open to the outside but can taste gas fume this way...

 

DUH valve in tester line sorry

 

ok did a wet compression test and got 12 or 15 lbs so it is definatly a ring bad and a overhaul .....sorry for the dip**** first post before doing the wet test ...