Hello everyone, I have a 1988 jeep wagoneer limited and I'm having an issue with my oil pressure gauge. The emissions testing facility wont even take it in if the gauge isnt working, which I kinda think is dumb since the gauge hasn't been working properly in a very long time and they've tested it before. But I'm trying to get the issue resolved and I'm getting nowhere. I've already replaced the oil pressure sending switch, and the gauge. When I replaced the switch, the gauge didn't move, it just stayed past 80 where it's been for a long time. When I replaced the gauge, the gauge was sitting somewhere around 20 before i turned the ignition on, then when i did turn on the accessory, the new gauge pegged out past 80 just like the old one did. There wasn't a change when the car was started either. Is there something else I'm missing? Any help is appreciated. I just haven't been able to find anything on this for anything older than a 1996 xj

 

I had the opposite issue:

https://www.cherokeeforum.com/f2/oil...gnosis-247764/

Turned out to be the sender. The system on my 96 sport works by grounding the sender. If you ground the wire to the sender, pressure gauge goes to past 80. Unplug it and it should go to 0. I would try unplugging it and see if you get 0. If not, I suspect you are grounding out before the sender. If you do get 0, it is probably your sender. Make sure you get the right one. MOPAR, not the cheap one (if it is the sender, don't just waste your money if you don't need one).

And not passing inspection is bogus. I'd go somewhere else if I were you.

 

Unfortunately with colorado emissions, I have to go to my county's emissions center and cant take it anywhere else. But I'll try what you've said and see if there are any changes. The gauge is hanging around the 80 mark right now but hasn't moved

 

If you replace the sending unit, it should work properly

 

I already have replaced it. But the problem could be the replacement part was from autozone and not a mopar product. The sender only has one wire, so I wouldn't be able to try the ground fix that was recommended right?

 

It works by grounding the gauge and metering the voltage with a small rheostat inside it. You might have another ground you shouldn't have in the printed circuit on the back of the instrument cluster. Or, as you say, cheap chinese stuff. It has been known to happen all too frequently

 

Yeah, the Autozone special is extremely unreliable for oil pressure senders. Do the test as Jesse mentioned and if the sender is bad, go Mopar.

 

I had the same issue last year with mine, and replaced the sending unit and it has been fine since then. It sounds like you have a bad (new) sending unit. Admittedly, I replaced mine with a NAPA one so far so good. I can't bring myself to spend dealer money on 20 year old vehicle. At least not as my first stop for a replacement part.

 

Make sure you get the sending unit and NOT the switch. Some parts monkeys dont know the difference

the switch is for the idiot light gauge clusters and will make the gauge peg out

 

Isnt the sending unit also the switch on my xj? Any time I look up the part, no matter the wording, it always comes up with the exact same thing. The part I'm thinking of is located almost right next to the oil filter and kinda looks like a fuel filter with one wire prong coming off of it. Is there another part that's apart of this? Cuz I dont think my cluster even has a light on it for the oil pressure

 

There are two different units, a sending unit for XJs equipped with an oil-pressure gauge which is a variable resistor, and the switch (either on or off with a pre-set minimum pressure) for XJs that only have a oil-pressure light and no gauge.

 

There are two instrument cluster options, one with gauges, and one with idiot lights. There are also two different sending units, one that acts as a switch to activate the light, and one that has a resistor to control the gauge. When I switched my cluster in my Jeep that came with idiot lights, the gauge pegged past 80. When I put the proper sending unit in, it works as a normal gauge. I used the Standard brand part, part# PS257. ($20.00 on amazon) No problem so far. I think it was like a 21mm deep socket to change it, but don't quote me on it.

 

Red1992xj, is the jeep you're talking about the same as your username? Aren't there a lot of electrical differences between 90's xj's and the late 80's xj's? I've been finding a lot of information on this problem with xj's that have a completely different "sensor" than mine does. Mine looks like the picture I attached

 

My apologies, I thought the sensors would be interchangeable. I did a little research on Rockauto, you would probably get the WVE/AIRTEX/WELLS 1S6563 sender. When you look at the listings, it will say either "light" or "gauge". You want the one with the gauge, obviously. If you go to a local part store, check their website first for an exact part#. New guys behind the counter wont give a hoot what they give you. I don't know what the mopar part would run you, but it'd probably be expensive, if you could still get it.

 

My suggestion is:

• Get a multimeter out and
  • Check power to the wire that goes to the sender. From what you said about the new gauge going from 20 - 80 this should be fine. You should see around battery voltage at the wire
  • Make up/connect a short lead to connect to the sensor for ease of reading
  • Check the resistance of the sensor itself so one probe on earth and one on the short lead. Take note of the reading
  • Start the engine and take another reading, this should be different to the previous
  • If possible get someone to rev the engine up and down and the reading should move with the RPMs

If the readings don't move then the sensor is faulty. If the readings move around with RPMs then it may be possible that it is the wrong sensor and is giving the gauge the wrong resistance to ground causing the mis-reading. I do not know what the correct readings should be however my gauge does work on my 95 XJ so if needed I could get the readings from mine to compare.