Ka24e chain has no tension oil light is on

[S13coupe_]

Hey I have a 90 240sx coupe with a stock ka24e my oil light turned on while driving and at first It was blinking and then it stayed on after the light stayed on there was a nose I later found out the nose was coming from the valve cover I opened it up and saw my chain was loose so I went out and got a oil pressure switch And a oil pump thinking it would fix the light and I put every thing back together started her up and still no tension I did notice when I would crank her over shut her off sometimes she would have tension I'm clueless to what's going on here does anyone know or have had this problem?