99 4.0L spitting oil

My cousin's 99 XJ 4.0L auto 4x4 170,000 miles starting leaking oil pretty good after he started it up two days ago after it had sat for a week. He said it had a rough time starting and sounded almost like it was missing and then smoothed out some. He said the oil pressure was reading almost nothing and then went up to about 70 after he gave it some throttle. Shortly after he noticed some smoke coming out from underneath and then he just cut it off and called me. I went by today and took a look at it. It definitely is leaking oil towards the back of the pan and dripping oil right on the downpipe where it makes its first turn from the header. The Jeep for sure seems to need a new oil pan gasket and rear main seal which I can do no problem. The thing that has me concerned is the oil pressure. I fired it up while I was there. It started and ran just fine. Reved it up a few time and watched the oil pressure gauge. At idle is was just over 40 and up to 3000 RPM it got as high as 60. I didn't go beyond 3000 RPM so I don't know if it would keep rising beyond that or not.

So other than replacing the seals, does thing sound like a failing oil pump or do we have a bigger problem on our hands?

I would stick another oil pressure switch on it see if that helps, and give you a better reading of what the pump is actually doing. Or better yet an oil pressure test guage. If nothing changes. Put a new oil pump in it while you have the pan off.

40 psi at a cold idle is pretty good and 60 over 3k is within spec.

CaliXJ said:

I would stick another oil pressure switch on it see if that helps, and give you a better reading of what the pump is actually doing. Or better yet an oil pressure test guage. If nothing changes. Put a new oil pump in it while you have the pan off.

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^^X2 Get one from the dealership. I don't trust regular part store replacements for this. Same symptoms happened to me. Replaced it from a local automotive store and crapped out in a few days. I replaced it with OEM part and it's been good ever since.

Leaky 4.0, normal.
40psi at idle, normal.

nothing out of the ordinary here.