Hello,
When I was leaving a store today I started the Jeep and it started shuttering, and sounded different. I looked at the oil pressure gauge and it was about 4ish psi. I turned it off, popped the hood and checked my oil. It was really high, like several inches high. I waited a bit, cycled the ignition a few times, and started her again. Seemed to be running ok now, and the pressure was about 10ish at idle.

Fast forward an hour or so and I am back to 4ish psi at idle, it would jump up and down a few psi while just sitting at idle. I drove home and my pressure was 19-20 while driving. I checked the dipstick when I got home, and same thing, verrry high. Oil seemed to not have water in it, and coolant level is fine, so I don't think it is my headgasket.

I read a few other posts related to low pressure and people mentioned the oil pump and the pickup tube, but I didn't see anyone mention a high oil level. Does that indicate anything obvious.

I have never had low oil pressure before, and the jeep doesn't seem to be driving any differently. Any ideas?

What kind of Cherokee? When and who changed your oil last? What oil filter are you running?

89 XJ with 4.0 L. I always change it, I think the last one was November? Not sure. Filter is a Fram PH3985.

I had a friend who had this happen to them. what he did was change his oil and filter. That seemed for the most part fix it.

If it's not oil in the crankcase, it's gotta be something, oil doesn't just magically expand.

So I did some reading about high oil levels and someone mentioned gas in the oil. I checked mine and sure enough it smelled like gas.

I changed the oil and filter. And checked the compression, which was good. As someone mentioned, this issues could be caused by not having combustion in a cylinder. So I replaced the distributor cap and rotor and made sure I was getting spark at each plug. I am getting great oil pressure know because the oil is not watered down from the gas. I will keep an eye on the dipstick level, because I kinda doubt it has been fixed.

What were your compression readings?

Worn rings can let blowby fuel get in the crankcase.

Check your fuel pressure, especially after a rest. A leaky injector can let raw gasoline get into a cylinder(s). Then fuel leaks past worn rings or scored cylinder walls.

Verify your pressure readings, ditch the Fram filter and use a high quality filter....

I don't have my notes with me, but the pressures ranged from 125 psi to 138 psi.

Is the fuel pressure worth checking if the cylinder pressures were ok?

Edit:

Cyl 1: 135 psi
Cyl 2: 126 psi
Cyl 3: 125 psi
Cyl 4: 129 psi
Cyl 5: 121 psi
Cyl 6: 138 psi

overfilling oil will cause a low oil pressure

http://www.dsmtuners.com/threads/com...esting.338152/

Pressure range for a 4.0 should be 120-150 PSI with no more than 30 PSI variation between cylinders.

Your #5 looks weak.

Although 121 is not great, it is within the spec, so shouldn't it be fine?

I picked up a fuel pressure test kit and followed the procedure in my Haynes Manual. Pressure was right on spec with and without the regulator connected, 31 and 39 psi respectively. I also did a leak down test and the pressure dropped from 39 psi to 29 psi in 30 minutes, which is well within the Haynes spec of 0-20 psi drop in 30 minutes.

I am lost.

121 is at the low end of the scale, barely before it becomes unacceptable. I don't term that "fine". "Fine" is more like your #1 and #6, in the middle of the range.

The gasoline is getting into the crankcase by some route for sure.

How many miles are on the engine?

Is your operating temp greater than 195 degrees?

145,000 miles. Operating temp is right around 200 F.

My plan is to pull the fuel rail, attach the injectors, turn the car on to pressurize it, and see if any injectors are leaking. I replaced the injectors with Bosch 703's about 18 months ago.