**help low oil pressure light **
 

Okay I have a 2000 Monte Carlo 3.8 non supercharged with 198000 miles on it and a low oil pressure light comes on but I change the oil pressure switch an the oil level sensor but the light still comes on . I can hear then engine knocking from the lack of oil. And sometimes it it won't start or just die after a few minutes...I use to have a oil leak around the oil sensor on the housing but I replaced it with another 1. While changing it there was a plunger with a spring. The spring came out and fell into the oil drip pan. I cleaned it off and put the whole thing back together but still no pressure. I don't the the tools to do a pressure test so I'm very limited on my resources..so any advice would be deeply appreciated....also when I installed a new pressure sensor is used Teflon tape and wrapped it all the way to the tip. .what I suppose to leave a bit exposed? ?..my next thoughto would be the oil pump but they rarely go out....so I'm clueless. ..thank in advance