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Unread 08-26-2009, 10:21 AM   #1
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1996 XJ Cherokee 
Join Date: Apr 2009
Location: Gaines, NY
Posts: 1,039
Oil Pressure Problem

ok so on my '96 XJ Sport 4.0L H.O. my oil pressure gauge is showing something strange.....it used to be at 0 when the engine was off then around 40 at an idle and go up a bit when i'm on the highway.....but recently the gauge has been saying 40 even when the engine is off (and has been off for a while) and says about 60 at an idle and goes up a little from there when I drive......

is it my gauge thats messed up or is it my oil pump or filter or what? is this a big problem?

'99 XJ Sport - The Green Lantern (sold) 4.0/AX-15/NP231/HP30/C8.25, 3" RC lift, 30's
'96 XJ Sport - The Red Zeppelin (DD) 4.0/AX-15/NP231/HP30/C8.25, 2" BB, IRO Front Hooks, Hella Black Magics
'91 XJ Laredo - The Grizzly Bomber (Trail Rig) 4.0/AW4/NP242/HP30/D35, 2"BB 31's
'91 XJ Briarwood - The Spruce Moose (Parting Out)
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Unread 08-26-2009, 10:52 AM   #2
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1997 XJ Cherokee 
Join Date: Aug 2009
Location: Marietta, GA
Posts: 341
Shouldn't all the gauges drop to zero when powered off ?

- _litz
1997 Jeep Cherokee Sport
1976 Fairmont MT-19
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Unread 08-27-2009, 07:03 AM   #3
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1999 XJ Cherokee 
Join Date: Feb 2009
Location: ridgway pa
Posts: 146
there is an oil pressure sending unit that sends the signal to the guage. i would say that the unit is going bad. its buy the oil filter. i pretty sure thay are cheep and easy to fix.
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Unread 08-27-2009, 11:01 AM   #4
It's the crank sensor!
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1999 XJ Cherokee 
Join Date: Nov 2007
Location: Central Minnesota, MN
Posts: 8,705
Oil temp sending units are a very common failure on the Jeep 4.0 engine. And when they go south, they often exhibit the symptoms you are describing.

Some guys temporarily put a mechanical oil pressure gauge where the sending unit resides to verify their exact oil pressure, but my bet is that a new sending unit will restore your oil pressure reading accuracy. It is located directly above the oil filter.

You might want to try cleaning the electrical connector to the sensor with electrical contact cleaner first before replacing it.

I would highly recommend purchasing this directly from Jeep for best accuracy/mating with your factory gauge. Many people including me have had mixed (poor) luck with aftermarket hardware.

Good Luck!
99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!
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