HOrnbrod Posted January 30, 2016 Share Posted January 30, 2016 For a couple of years my oil pressure gauge has been reading high. On startup it pegs the gauge at 80psi, then after it warms up it settles down to 65-70psi. I tried three different aftermarket sensors from various manufacturers, all the "fat bellows" type, and they too all read way high. I did hook up a mechanical gauge temporarily just to verify, and it indicated right at 50psi on a warm idling engine, so I figured my gauge was off and didn't worry about it. I spotted a NOS Mopar sensor last week on Ebay and grabbed it for $19 and stuck it on. Now on startup, a cold engine reads 65-70psi, then settles out at 45-50psi when warmed up, agreeing with the mechanical gauge. Goes to show you can't beat genuine Mopar parts. So if you're having wonky oil pressure readings, try a Mopar sensor first. :thumbsup: Link to comment Share on other sites More sharing options...
cody4359 Posted January 30, 2016 Share Posted January 30, 2016 Hmmmm. My low oil/Check engine light comes on for about 1sec before the oil pressure rises after its sat a day or more on the initial start up but it's fine after that. Wonder If that could be my issue Link to comment Share on other sites More sharing options...
Dillithium Posted January 30, 2016 Share Posted January 30, 2016 I have the same problem! It always reads 80/full when cold, it takes about 20 minutes of driving for it to read 45-50 on idle, and 60-65 cruising. I'll be looking out for one, thanks Hornbrod! Link to comment Share on other sites More sharing options...
91Pioneer Posted January 30, 2016 Share Posted January 30, 2016 My gauge is maybe wonky (or it's the pressure itself). What is the part #? My gauge cluster came out of a 93/94 XJ and I grabbed the sender out of there too. Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 30, 2016 Author Share Posted January 30, 2016 The 91 sensor p/n is 56026782, not 56026782AC (this is the new p/n and is the bellows type). It has a single spade output terminal and looks like the one in my pic above with a black body. Link to comment Share on other sites More sharing options...
91Pioneer Posted January 30, 2016 Share Posted January 30, 2016 Is that the same part # for 93/94 XJs, do you know? Would it matter? I'm going to have to go look at mine again because the factory wiring plug did not fit the XJ sender I got. Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 30, 2016 Author Share Posted January 30, 2016 The 1991 MJ/XJ sensors (56026782) were the only ones with the single spade connector. The 92-96 sensors (56026779) have two terminals so they wouldn't work w/o the proper connector on your harness.. The Euro version sender (56026781) has a single stud connector so that would work if you crimp a ring terminal on the output wire. Link to comment Share on other sites More sharing options...
gogmorgo Posted January 30, 2016 Share Posted January 30, 2016 Yeah, that. When I swapped the '93 motor in, the pressure sender was something I had to reuse from my '91. Link to comment Share on other sites More sharing options...
Minuit Posted January 30, 2016 Share Posted January 30, 2016 What do you mean by "fat bellows" type? The aftermarket sender I just put on mine (Standard Motor Products PS315) looks exactly like yours and seems to work fine, or at least believable (60-65psi cold idle, 35-45ish warm idle) Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 30, 2016 Author Share Posted January 30, 2016 Yes, I saw some aftermarket senders that looked like the Mopar units but I don't know if they have the same outputs across the pressure range. :dunno: Maybe, maybe not. Link to comment Share on other sites More sharing options...
Crash Posted January 30, 2016 Share Posted January 30, 2016 For what it's worth, I have had success with the Carquest blue box sensors (Made by Wells) Link to comment Share on other sites More sharing options...
91Pioneer Posted March 5, 2016 Share Posted March 5, 2016 For what it's worth, I used a 92-96 sender on my 91. It is actually just a single wire unit even though there is space for an extra wire and terminal (it's just plain missing). I used the wiring pigtail from the 92-96 XJ and crimped on a spade terminal to tie back into my factory 91 wiring. It may not be pretty but it works great and was a lot less than the $45 RockAuto wanted for an aftermarket sender (CDN w/shipping). The 92-96 sensors (56026779) have two terminals so they wouldn't work w/o the proper connector on your harness.. Link to comment Share on other sites More sharing options...
TheDude Posted March 5, 2016 Share Posted March 5, 2016 My oil pressure reads 70 on a cold start then goes all the way down to 20 when the oil fully warms up which seems to take a while.. Link to comment Share on other sites More sharing options...
Eagle Posted March 5, 2016 Share Posted March 5, 2016 My oil pressure reads 70 on a cold start then goes all the way down to 20 when the oil fully warms up which seems to take a while.. That's normal. The guys above reporting 45 psi at warm idle are the ones that are unusual. Factory spec for oil pressure is 13 psi minimum at warm idle, and 37 to 75 psi above 1600 RPM. Based on having driven well over half a million miles in XJs and MJs with the 4.0L engine, every new one I've had over the years has showed warm idle around 25 to 30 psi, and runs (warm) at 50 to 55 psi at highway speeds (which for me means 55 to 65 MPH). Link to comment Share on other sites More sharing options...
gitslashgin Posted March 6, 2016 Share Posted March 6, 2016 I've put a baffle style on my 1989 MJ after replacing the original with a non-baffle style twice. Each of the non-baffled sensors pegged to 80 and stuck there regardless of rpm or heat. As of now my gauge reads at/around 50-65psi almost all of the time (unless the truck isn't running ofc). I do know that my 4.0l has lost compression in at least cylinder #1 and it leaks oil from the rear main like a stuck pig. However, I now have a buildable replacement 4.0l in my garage with significantly less miles. Would that baffle-less mopar sensor be my best bet for accurate readings in my MJ after the swap? Link to comment Share on other sites More sharing options...
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