"after a few pumps pressure is applied to pump arm forcing it down."
Pressure from where? What is forcing it down? If there is pressure being applied to the arm and its dropping on it own, it seems to me that the check valve maybe be leaking. Pump it a few times, then turn it upside down with the pump arm about 3/4 closed. If the arm opens on its own the chack valve is bad. Air pressure is slowly escaping from the valve and pushing the rod back, opening the arm.
If the check valve is ok, adjust the linkage so that the pump head makes contact with the valve face when the handle is about 1 inch from closing and you need to snap it closed a bit.