Ok I got a 93 xj sport with the 4.0 it has a slight oil leak I've replaced the valve cover gasket doing the oil filter today but still can't keep any oil pressure i also replaced a oil pump

 

Change the sending unit

 

Does any oil pressure show up when you first start it? If not... x2 on the sending unit.

 

Any idea on what that will cost also will a rear main cause bad oil pressure and I only have oil pressure when I first put oil in it

 

Price depends if you have the gauge or light. Im guessing you have the gauge and it is $30 from advance. The sender for the light is $11

 

Us the gauge I've never done one where is it located

 

On a 93, not too sure. Should be somewhere near the oil filter. On my 98 its right above the filter. Its not hard to find.

 

Alright thanks

 

I'm troubleshooting a low oil pressure reading. I've got a 97 xj country that's running fine, then dropping to 10-15 psi at idle once it's been warm for a while.
My recent history with this issue:
I bought from my brother. He had Jeep dealership test oil pressure in engine @>127k mi: 40psi.
(I don't know if the motor was warmed up when they ran this test.)
Oil & filter changed (10w-30, mopar filter) @ 127,800 mi
Oil pressure dropped to 18-20psi at idle after ~50 mi of driving.
Oil pressure sensor sending unit replaced @ 127,900 mi
Overheated 2x on a 300 mi highway hop, not driving fast.
STP oil treatment added, Serpentine belt replaced, Thermostat replaced & Radiator flushed @ 128,000 mi
ran warm, but oil level's okay, coolant's okay.
I had a mechanic look it over @128,500.
He said the idle oil pressure should be 20 psi & XJ's aren't known for blowing their oil pumps.
Since then, reaching 129k, the engine still gets warm (showing ~230 and the oil pressure is now reading 10-15psi when it's warmed up. If 20 psi is normal, then 10-15psi isn't healthy for my motor, right?

My oil pump is the original & 14 years old. Nothing lasts forever & I don't like to wait for things to break. If it's a safe bet for an aging motor, I'll do it in a few months, but if this sounds like something else, please offer opinions. No sense putting a new oil pump on and then replacing the motor and needing another new oil pump.
I'm also looking for recommendations for what oil to use at the tender age of 129k.

I have had several mechanics looking at this with me over my 1500 miles of ownership and this is what we've done/observed. I hope this helps you with ideas of what to look into.

 

K thanks

 

There's a difference between a low oil pressure reading on the gauge and really having no oil pressure.

If the gauge reads low, it would be a good idea to install a mechanical gauge temporarily and determine if the engine has oil pressure.

If the mechanical gauge shows oil pressure within allowable range, it is probably the sending unit that has failed. Replace it and you're done if the reading goes back to normal.

If the mechanical gauge confirms little or no oil pressure, it's time to look deeper. It could be as simple as very low oil level, it could be that the oil pump is shot or the engine may need a complete rebuild because there is too much bearing clearance.

If I had no oil pressure, I'd be inclined to look for a good condition used engine before considering a rebuild. It's possible that replacing the oil pump will solve the problem, but if the engine ran for any length of time with low/no oil pressure, there is likely bearing damage.

I prefer to be able to hear the engine run and observe good oil pressure before parting with my money. Look for an engine out of a well maintained wreck. Look in the oil cap and see if the rockers look clean. Look at the underside of the oil fill cap and on the dipstick for any milky deposits. Listen to the tailpipe for any sign of misfire. Look at the condition of the coolant. It should be bright green and not look like muddy water.

 

Its probably due to my oil leak then in April I'm dropping a new engine and transmission in it

 

Low oil pressure isn't because of your oil leak unless your oil level goes down dramatically.

If you really want to know what your oil pressure is (and you should), rent a mechanical oil pressure gauge from a big box parts store for a few bucks. Temporarily install it where the oil pressure sending unit currently resides (above oil filter).

Then you'll know. Good data = good decisions.

Oil pressure spec for the 4.0 is as follows:

*Not less than 13 psi at HOT idle
*Between 37-75 psi over 1600 rpms

If you are out of spec by much on the above, you most likely have bearing problems in the engine.

 

Ok thanks

 

TJWalker & WildBill1, thanks for the specifics. Kryptic11, hope you get your motor situation straight so you can get your jeep on.