ok guys ive got a 01 silverado with the stock 5.3 in it at around 128k miles...the truck has longtubes,3600 stall,224 cam,241 LS1 heads ect...well i drove it to work about a month ago and when i went to get dinner i come out after eating and crunk the truck up it had no oil pressure...it had oil pressure when i parked it...i thought the sending unit might have went out and since i live 3 blocks from where i was eatin i was gonna see if i could ease home with it hopin it was just the gauge...well by the time i got on the road it already had alittle lifter noise so i just shut it off and pulled it home....my question is what will make a oil pump just go out when you crank it...i put the cam and stall(and new trans) in it when i got the truck about 6k miles before the pump quit...any hints on what might have caused it

 

I believe that the pressure relief valve can get stuck or fail without any warning

 

Get it checked, I just replaced the sending unit on my truck and talking with the mech he said he's seen several pumps fail out of nowhere.