Bakerxj

I have an 01 xj. About a week ago I was sitting a a red light and my check gauges light came on and I saw that my oil gauge was at zero. The light turned green so I went and the gauge went back up to 40 came to another red light and the gauge dropped back to zero. I changed the oil and cleaned the oil sending unit. Does anyone have any ideas? My dad says it could be a worn main bearing and there's a gap between the bearing and crank shaft.

And go!

Bustedback

Check the oil pressure with a manual gauge that screws into the port that the sending unit screws into. 13psi is the minimum at idle and the rule of thump is 10psi for every 1000rpm.

dmill89

While worn bearings is a possibility, the oil-pressure sending units are notorious for failure and a failed oil pressure sending unit is much more likely. Verify the pressure with a mechanical gage (I think they are around $20 at harbor freight and you can rent/barrow them at many auto-parts stores) and/or replace the oil pressure sending unit (about $40, an OE one from the dealer is highly recommended) before jumping to any (expensive) conclusions.