Ok guys, I did some searching. And I have yet to find any kind of answer to point me in the right direction.
My 2000 XJ is having, what I think, is oil pump problems.
Under normal driving conditions, about 99% of the time, my oil pressure is PERFECT. No issues what so ever. Runs about 60 under load and roughly around 25 to 30 cruising... 10 to 15 at idle.
I noticed the other morning going to work while I was sitting in traffic that all of a sudden my CHECK GAUGES light came on and I had 0 oil pressure. I paniced and shut the motor down. I got out and checked everything over and visually, things looked OK.
I started the Jeep back up, perfect oil pressure. After some more head scratching I drove on to work. A few days later, it did it again!
The condition is this....while at idle for more than a minute. My engine's oil pressure drops to 0! However, works perfect at all other points in time. And when the engine drops to 0, you can slightly rev the engine to ~1000rpm and viola! oil pressure comes back. Something else that is wierd...it does not do it all the time. It is sporadic, seeming to do it only when the engine temp is at normal operating temp.
The vast percentage of strange oil pressure readings are caused by a faulty oil pressure sending unit as already mentioned. If your oil pressure truly was zero, you'd probably be hearing some engine noises. Some guys just replace them as they're cheap (I recommend buying from Jeep for best gauge mating accuracy) or if you're ambitious, get a hold of a mechanical gauge and temporarily hook it up where the oil pressure sending unit is and compare readings to what you're seeing.
99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche Without "data", all you have is an opinion!
Yep, Just freaked out today when the wife called and said her oil pressure was at 0. Hooked up the manual gauge and it was perfectly normal. In the process (actually when I first took it out) I noticed that it had a bunch of oil in the electrical plug side of it. Good news to me, I almost had to buy my neighbors Cherokee that has a new bored out 4.0 and a lift already....lol
Agree on the sending unit, especially if its OK after a shutdown and restart. They leak oil past the internal diaphragm, and when enough oil builds up on the backside, they read 0 pressure. Turn off, oil forces its way back out and they're good again for a while. Pretty common failure on any vehicle with an electric oil pressure gauge.
That said, NEVER roll the dice with oil pressure. If it really does go to zero, your engine has about a minute (or less) to live without damage if you're driving. A little longer at idle/no load.