Hey all probably a dumb question but my 2000 xj 4.0 with 142k miles just started doing this the other day. When I turn the key to the "on" position the oil pressure gauge jumps to 50 psi before starting. Once running it pegs out at 80 psi and pretty much stays there I'm figuring the gauge is off by 50 psi but what could be causing this? Thanks in advance

 

Pretty common when the oil pressure gauge sender has failed.