A different oil pressure problem

So my best friend (Jim) picked up an XJ today...

On the way home oil pressure gauge went to zero... he pulls over, and calls the towtruck. Meanwhile on the phone with the seller, seller says the gauge was bouncing around for the past couple weeks and he thinks the sensor is bad.

So, I go over and check it out... you can skip this if you want to get to the point.
'94 Country auto
dark blue and tan bottom
tan inside
good paint and interior is really good
windshield has black goop on top moulding
crappy car tires
NP 242
"high clearance" rockers in his words (auto cancer has taken its toll)
..but the floors are solid.

the point
Back at the shop, Jim starts his new pride and joy up, and oil pressure gauge reads ~40psi. Jim says it was a quart low upon purchase, and added a quart when he picked it up and checked and it was good. I pull the oil cap to see if there's a mist coming out of the valve cover while it's running, and there's no mist. Just the rockers doing their job, and a film of oil (or residue) on everything.

I know some cars have more of a 'oil mist' than others, and I'd fire up my Jeep if it had a fuel pump, but no. So, I need someone to pull the oil fill cap and run their jeep for a minute and see if there is an oil mist. I figure it's easier than having Jim pull the oil pan and look for chunks.

Any help would be appreciated.
-Matt

No mist on my 89 or 93. I'm betting he just needs to check the wiring to the oil pressure sender and maybe replace the sender. Its right next to the oil filter and its not too hard to accidentally hit the wiring while doing an oil change. Plus the senders are mechanical inside and do eventually wear out.

I agree with lawsoncl; this is most likely a sending unit problem. Could try cleaning the connector for the oil pressure sending unit with electrical contact cleaner, but you may end up replacing it. A very common failure on the 4.0. Replacement is a 10 minute job.

I HIGHLY recommend purchasing this part directly from Jeep for best reliability/accuracy/mating with the factory gauge.

somehow my sender ended up being from a chevy something at the parts store...i can get car quest part number if you need one

had the same probleem with my 94, replaced the sending unit with one form oreilys and the gauge bounced around even worse, installed a mechanical gauge to make sure and oil press. fwas good, got a sending unit f rom the dealer and both gauges read the same ever since, i would suggest using a good filter as well, not fram

My new oil pressure sender (OEM) has read almost 80 pounds of oil pressure all the time since I got it...I just didn't worry about it, as the motor runs great and makes no strange noises.

mynameisphunk said:

My new oil pressure sender (OEM) has read almost 80 pounds of oil pressure all the time since I got it...I just didn't worry about it, as the motor runs great and makes no strange noises.

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So I guess you're implying that you OEM sensor isn't any good. It reads 80 when cold and 80 at idle when hot? If so, it isn't any good.

winterbeater said:

So I guess you're implying that you OEM sensor isn't any good. It reads 80 when cold and 80 at idle when hot? If so, it isn't any good.

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That sounds like an idiot light sender, not a gauge sender.

sounds like the oil pressure sender, as stated above. Costs $20 from 4wd.com. I just bought one a few weeks ago.

my buddy uses motorcraft oil filters (I think champion labs, aka penzoil filters, and lots of others) as he works at a ford dealership.