[dana44]

Welcome to the forum. It is time to put a manual oil pressure gauge on the engine to ensure it is indeed no oil pressure. The tap for the pressure is on the back of the block edge on top, above the transmission case. There should be an oil pressure sensor there, about the size of a plum with a wire on the top. Oil pressure just doesn't disappear when you change the oil, unless there is something inside the oil pan that was able to cover the pick-up in the pan, or, the valve stem seals over time become hard and break into bits, cleaner oil could have allowed them to then be able to get sucked up into the oil pick-up and plug it up. So, check the pressure first, drop the pan and chances are good this is where the problem would be.

 

[Bob Lincoln]

You probably knocked the sending wire loose when you changed the filter. If the sending unit is next to the filter, you'll probably find a dangling wire there that you can just plug back in.