Stuck open or closed? I had the piece fall out once, but I pushed it back in and peened over the edges. They took off the oil cooler and I checked the valve, it still pushes up with finger pressure. Pick up tube was checked for leaks, new gasket, Melling high volume pump, and new cam sensor. Starts right up if you fill the tank with oil, but isn't building oil pressure. Took a fitting off near the oil filter and blew air into the hole. Air comes out the oil tank for the HP pump, but doesn't bubble out into the oil pan.