oil pressure not good. Some opinions please.

We are dealing with my 96xj with the 4.0HO. Last week I was driving to town and noticed my pressure was not normal. Normal was around 50 to 60 at startup, 30 to 40 warm at highway speeds, and 10 to 20 at warm idle.
This is a 15 mile drive there and back. On the way there it would be around 25lbs. at 50mph and at idle between 0 and 5lbs. It would go up when getting on the gas but would drop once at speed.
Then on the way home it got worse and when almost home I could not even get any pressure to show at all but everything sounded good and there were no other problems. I took it for a short ride after and still no pressure but ran fine.
I am thinking a sending unit is in order but could there be something else wrong I am not looking into? I will be going out to the garage shortly to start it up and see if there is any pressure at cold startup. I haven't started it in almost a week.
So any thoughts or suggestions are welcome. Thanks.

Kim.

No rappity-rappity-rap at idles when the gauge reads 0?

I would think, and replace, the sendor 1st.

Rev

Rev Den said:

No rappity-rappity-rap at idles when the gauge reads 0?

I would think, and replace, the sendor 1st.

Rev

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There was no abnormal clicks, ticks, knocks, or anything. That is what makes me think the sending unit. But is this something that happens when the sending unit goes out? Just all of a sudden? Don't know myself, I have never had to replace one yet. Thanks Rev.

Kim.

Just had it started in the garage. Pressure at startup was 40 and within seconds began to slowly go to 0 in less than two minutes of letting it idle. Everything ran fine even at normal running temp. No knocking or anything just no pressure reading. So it looks like I will be replacing a sending unit Friday night.

Kim.

85xjwoody said:

But is this something that happens when the sending unit goes out? Just all of a sudden?

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Yup.

Anytime.

Rev

x2 on rev's advice, it's cheap and easy to change. mine dropped like a rock after i went to synthetic oil, i changed it and it's been fine for 7 years.......

I took the jeep for a ride this afternoon and now my oil pressure guage is working but it moves around more than it used to. At warm idle it stays between 30 and 40 but moves everywhere inbetween. At speed it stays above 40 but is always going up and down but not below 40. I still think that the sending unit is the culprit here. I hope.

Kim.

when i got the 6 guage cluster, and put in the new sender, it was a little erradic too. its settled down after a couple weeks.

I had a motor home (Ford 460) do this somewhere between Flaming Gorge Res. and Salt Lake. Stopped at a NAPA in some little town and installed an analog gauge (with the plastic capillary line). The Ford gauge was all over the place - scared the crap out of me. The analog gauge showed normal pressure at all RPM's. It was a bad sender. I still haven't changed it out (can't find the damn thing), and it still acts goofy, but the engine oil pressure is good. Since you have no other symptoms, my money is on the sender. Have fun.

jayuu said:

when i got the 6 guage cluster, and put in the new sender, it was a little erradic too. its settled down after a couple weeks.

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I have not put in a new sender yet. Maybe Saturday if I can find time.

Kim.

85xjwoody said:

I took the jeep for a ride this afternoon and now my oil pressure guage is working but it moves around more than it used to. At warm idle it stays between 30 and 40 but moves everywhere inbetween. At speed it stays above 40 but is always going up and down but not below 40. I still think that the sending unit is the culprit here. I hope.

Kim.

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If the sending unit turns out to be OK, the next most likely possibility is that the oil pressure relief valve inside the oil pump is malfunctioning. Instead of trying to fix the valve, you'd be better off getting a new oil pump.

Dr. Dyno said:

If the sending unit turns out to be OK, the next most likely possibility is that the oil pressure relief valve inside the oil pump is malfunctioning. Instead of trying to fix the valve, you'd be better off getting a new oil pump.

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Thanks Dr. Dyno. I will find out soon about the sending unit. I sure hope the pump isn't the culprit. Almost $100.00 for a new one. When I change the sending unit I will be replacing the oil and filter with a new Baldwin filter. I just don't trust anything besides a Baldwin. Most others have failed on me so the oil filter could be a problem too. Change the cheap things first then let it get expensive.
Oh yeah, did I mention this motor was hydrolocked once before. I think alot of headaches are starting to show up. Possibly time for a stroker if this motor goes.

Kim.