Dumb question:

Where is the oil pressure sending unit located on 2.5L I4? ('93 Wrangler S 5spd if that's important).

My guage was giving weird readings that didn't make sense (i.e. were not representative of what oil pressure could really be doing - 80psi to 40 psi bouncing needle), and now it's sitting below 0 psi, I'm REALLY REALLY REALLY hoping that the wire came loose or something. Otherwise I've put about 200 miles on her with no oil pressure, and I'll be checking the For Sale forum for a 4.0 I6 upgrade soon...

Some years ago I was experiencing the same symptoms in my S-10 Blazer. One day I noticed that the oil pressure guage was all over the spectrum and then one day it settled on 0 oil pressure. I had a hunch was it was and my mechanic confirmed it. The main bearings spun and was blocking oil flow. Things went down hill from there. I ended up replacing the engine. I believe the X is still driving it.

Realy? Main bearing blocking pressure from the sending unit...
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

i had somthing like that happen to my 86 cj...i just took the sending unit and the guage out and replaced them with a guage that didnt require a sending unit...just had to run the small tube through the dash to the new guage..and all was better... <img src="/forums/images/graemlins/cheers.gif" alt="" />

Them is called "mechanical gauges". Back in the days when vehicles came with no gauge and only a RED LIGHT when the pressure was low.. I installed a bunch of them things.. And yes if the 1/8" nylon tubing does not go away they are great.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

I'm fairly sure it is on top the filter housing. It is on the 4.0's. Most other engines have it there.

most likely that will be your problem a very common issue with the jeeps. they are close to the filter so they are prone to accidental bumps and such from oil changes( i replaced mine once and alot on customer jeeps). hopefully it is just your oil pressure sensor good luck

Ok, I found it, it's above the filter but on the other side (towards the front) of the distributor. The "plug" that holds the wire in place was sticking out... I tried to put it back in and started the engine; the gauge went up to about 10 psi and then dropped back to 0... I looked again and the plug was hanging out again. Fortunately it's not spraying oil all over the engine compartment, but I'm pretty sure I can just replace that and be done. Looks like $27.99 from Checker.

Re-upping this post.

So, as I was posting all of this stuff, my wife was leaving me. I got the house and the Jeep, she got the Ford Focus. <img src="/forums/images/graemlins/butwiggle.gif" alt="" />

Anyway I replaced the sender and all seemed fine for about 3 months (though the pressure seemed to read high) then same symptom. Another new sender and it's been stable for about 2 years, but it consistently reads very high pressure (40-60 psi at idle depending on temp, pegged over 80 at anything over 1500 rpm).

Do I have a "bad scale factor" in the cheapo Checker sender or do I have a blocked oil passage somewhere? How can I "quickly" check what actual oil pressure is? Unscrew sender and put some sort of "trusted" guage in its place, for example?

Oh, yeah, I've put a good 20k on this little 4banger since the original post, so at least that's positive! <img src="/forums/images/graemlins/kewl.gif" alt="" />

Welcome back Greggy!! I never have worried about high pressure.. For sure it is a lectric problem. Maybe you have some oil leak on the connecting wire?
But if you are worried go get a standard 100 lb 2" pressure guage that is used on water wells and air compressors.. I'd even borrow one I have on one of my compressors now!
It should be easy to find a way to screw it into the sender hole threads with an adapter if sorts.. Then start her up and watch the actual pressure.
I never worry about pressure until my lifters run out of oil and start YELLING at me.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />