My oil pressure guage on my '98 Cherokee Sport 4.0L ranges from 40 at idle to 10 when decellerating for a stop. It increases as I accelerate. Sometimes when I start up, my check guages light comes on and the oil pressure guage doesn't move. After 30 seconds or so, it sometimes kicks in and runs up to 40, sometimes I turn off the motor and wait 30 to 60 seconds and start again. Somtimes the pressure guage shows pressure right away, sometimes I have to wait again and it kicks in showing pressure. It was suggested to replace the sending unit, which I will do if I can figure out how to unhook the electrical from the old one. Any other ideas if this doesn't work?

 

I put in a mechanical guage which actually came in handy recently when my stock one quit.

 

At least check the oil pressure with a mechanical guage...don't trust the stock set-up.