Oil Pressure guage acting funky

[Marine1Texas]

Ok 87 4.0 manual 4x4 renix with full cluster of gauges. The oil Pressure gauge when off or with key in is saying 20 PSI. I disconnected the lead to pressure sensor and it stays the same, so I am looking at a guage that is not resetting to 0.  I also made sure it was not sensor by using a old one for testing same results. So at idle it says 55 to 60 psi and when driving is from 75psi and goes all the way over pass 80 to what would be 85. Basically about 20 higher then it really is

 

It just started doing this yesterday, when I had to pull 10k hay bales trailer 65 miles to Quinlan. I pulled over to check everything once I seen it acting weird. No excess oil in pcv valve or hose, and no excess oil coming out of the filter for the valve cover. oil level is full and golden color. The engine running at a nice 205 no up or down, and not a single oil drip.

Today I drove it down to Houston to pickup some parts a 460 mile round trip had not a single issue doing 75mph there and back.

 

So I am thinking something in the cluster is messed up. Anyone know of away to repair the gauge? or am I looking at looking for another cluster. All the other things work on the cluster fine and reads very close to what is.

 

 

[Ωhm]

Either you have excess resistance on the sending unit side of the circuit or a faulty gauge.

[Marine1Texas]

I think I am going to start looking for a new cluster.

[87MJTIM]

I've learned not to trust the gauges. A few times the gauge was reading 20 psi while running at speed.  At idle it would drop to near zero.

 

I swapped out several clusters until I found an oil pressure gauges that reads (some what) correctly.

[Minuit]

The individual gauges can be replaced, but at that point... might as well just grab another cluster unless you have a supply of known good gauges for some reason or it's the rare '87 only blue full cluster with the late speedo connection. I had this problem on my '87 blue full cluster in my red truck - the temp and oil pressure gauges were reading way too low. I used gauges from an '88 3/4 cluster and it works fine now.

[Strokermjcomanche]

Double check to make sure it'll work 

 

https://m.ebay.com/itm/NOS-1984-86-AMC-Jeep-XJ-Cherokee-MJ-Comanche-In-Dash-Oil-Gauge/232585429651?epid=2240590132&hash=item36272c0293:g:dGoAAOSwm-pZtU5h

[Marine1Texas]

When I pulled the thing out today to check on it, everything seems like it is almost 1 piece. It is the blue case. I can see if you unsolder you can get it out after you take the few screws out. For now I just installed after market electric one I had on a old tractor that needs rebuild. It fit the oil sender port on the engine and reads about where it should be. I have it tie strapped in place just over the steering wheel.

 

To me the temp and oil are needed. We spend at least 10 hours a day in the back acreage in it. Running from one place or another to get work done. In the amount of mileage we have put over the last 30 years on it, it holds up great. I think we can make it to 500k easy before it needs a rebuild. Seems like the sensors are the biggest issue we have ever had on it. You can push it hard all the time and it never skips a beat.

   

[jeepdude89]

Mine in my 88 MJ was acting weird-getting stuck, giving false readings etc until I cleaned my C101 connector. Has been working great and has been accurate since.

[Marine1Texas]

I have non c101 I bypassed it years ago and have everything wired direct. Since day one in Nov 1987 the truck had those wiring issues in the c101. we took care of that long ago. Plus we added a extra piece of sheet metal that would catch and push away any drippings from the master clutch over the fuse box. I have done all of the cruiser tip type stuff, and then some more. We have redone every ground either with larger grounds wires and cleaner spots as well as created a 2 gauge ground wire running thru frame that I have each near by ground connected to.