'96 Cherokee oil pressure gauge--wacky

Yesterday I was on the way to the auto parts store when the oil pressure gauge maxed out. I turned off the engine and the pressure gauge stayed maxed. While the jeep sat at the parking lot, the pressure went to zero.

On the drive, the oil pressure went to about 70 psi and then right before I got home, maxed the gauge. I shut off the engine and the gauge stayed maxed.

As I was doing an oil change (hence trip to auto parts store), I pulled the filter and drain plug. Pressure stayed maxed.
Disconnected sensor - gauge maxed
Disconnected battery (sensor still unplugged) - gauge maxed
Turned ignition on with batter disconnected and sensor unplugged - gauge maxed.

After changing filter and oil, reconnected battery, oil sensor, started engine. gauge went to 70 psi. Shut off engine and then put the key to the pre-start position, gauge stayed at 70. Switched off the key, switched on key and oil pressure went to zero. switched key off and gauge remained at zero.

Started engine, pressure went to 65 - 70 psi, but when I shut off the engine remained and would only return to zero when I would turn the key on (pre-start position) and then back off again.

Long story short, is this the sender? To me it sounds like it might be the gauge in the cluster rather than wiring to the cluster. Anything else I should check before I decide what might be the issue.

I really hope it is the sender as it is much easier to fix. Does anyone know if the oil pressure gauge can even be changed in the cluster without a lot of pain?

Anyone know what voltage range the gauge is looking for?

BTW, I installed the cluster out of a used '94 about 6 - 8 years ago. Still think it was stupid of them not to put a tach in a vehicle with a manual transmission.

Tom

well i do not exactly have the answer to your question but i can tell you that me and my girlfriend have a '96 Xj that has been doing the same exact thing that yours is doing for a while now. I changed the sender when this first started happening and it did'nt change a thing. Its been about 8 months now and the jeep still runs great, i just told her to ignore the whacky gauge. the jeep has been on a couple big mileage road trips with this problem and it never skips a beat. i just have'nt classified it as a big enough problem yet to do anything about.

When it maxes, the sender is flaky.

They gauge is supposed to "freeze" when you turn the key off. When you turn it to ON, (pre-ignition) the gauge is supposed to drop to zero.

Anyone have the info on what range and values of the transmitter (sending unit)? If it is the transmitter, I should be able to pull the unit, hook it to a pressure pump and then measure the appropriate values. All one needs is a 0-100 psi rig and it can be done with a regulator and air pressure, then hook a multimeter up to the output.

Like wise, I could make up my own signal generator and hook it to the transmitter wire to the gauge to test out that portion of the circuit.

Make sure the plug is seated all the way in the sender. Mine maxes out if I don't plug it in all the way after an oil change.

OK... my '96XJ just started doing this exact same thing this past week. Did you ever find the fix?

Also, where exactly is the oil pressure sending unit located? My XJ is due an oil change this week so I want to make sure I double check everything and get this fixed. I don't like ignoring gauges that I know are wrong or are acting flaky... I'd rather they worked like they're intended.

No need to find fix, we Know its the Sender! On the 96, it is right next to the oil filter where the connection plugs in. As a temp fix you can remove and clean connections.

OK... feeling STUPID!! I popped the hood on the XJ when I got home f/work yesterday to discover that my Oil Pressure Sending unit had simply come unplugged.... Plugged it back in and whalah... the gauge works as it had before.

Guess w/all the stuff that's gone on the past 2 weeks my oil pressure gauge was on the lower end of the priority scale... record ice-storm and power outages here in OK, all the down Pecan Trees around my property, etc... so long as the XJ kept running I was happy... lol.

I just picked up a 91 XJ on eBay with this same problem and also the volt-meter reads about 16 volts when running. Prev owner stated both systems had been manually checked and were normal. Could the problems be related? I haven't yet had time to get under the hood to check anything.

HAVE 96 XJ OIL PRESSURE WENT WACKY TOO, ABOUT 4 MONTHS AGO , WENT TO THE ZONE AND GOT A NEW ONE WAS FINE FOR A SHORT TIME , WAS POS BRAND . WENT TO A MOM AND POPS PARTS HOUSE TURNS OUT THERE ARE AT LEAST 4 DIFFERENT ONES , CANADIAN MODEL, AMERICAN , AND DIESEL , OH AND EUROPEAN, SOME ARE ONE AND SOME ARE TWO PRONG . ENDED UP WITH A STANDARD. HAS TWO PRONG , EUROPEAN HAS ONE .