Oil pressure issue

wardogg

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Recently purchased 2002 Wrangler X. 168k Completely stock as far as I can tell. Day 2 of owning it, after about 180 miles of driving it, the oil pressure dropped to zero with the associated check gauges light while idling at a stop light. Revved engine and pressure climbed back to normal.

Got it home and changed the oil sending unit. Oil change. New filter. For the first test drive it seemed ok. But by time I got it back in the driveway while sitting at idle it slowly loses pressure. Now not all the way to zero. But down around 20psi. While idling it is a very slow decline and takes a bit to get there. Giving some rpms brings the pressure back to around 50psi. No pressure issues while driving.

What are the chances I bought an engine problem? Is it safe to drive while I figure it out?
 
Recently purchased 2002 Wrangler X. 168k Completely stock as far as I can tell. Day 2 of owning it, after about 180 miles of driving it, the oil pressure dropped to zero with the associated check gauges light while idling at a stop light. Revved engine and pressure climbed back to normal.

Got it home and changed the oil sending unit. Oil change. New filter. For the first test drive it seemed ok. But by time I got it back in the driveway while sitting at idle it slowly loses pressure. Now not all the way to zero. But down around 20psi. While idling it is a very slow decline and takes a bit to get there. Giving some rpms brings the pressure back to around 50psi. No pressure issues while driving.

What are the chances I bought an engine problem? Is it safe to drive while I figure it out?

If you raise the revs and the oil pressure goes up to 50psi then your oil pump is working. You may have bought a TJ with oil presser sender fault. if you are reading 20psi at idol and it raises with revs then its fine. below 15 is not so good and zero on a working engine without eventual bearing knock is a sender fault.
 
No worries, your oil pressure is fine and it is supposed to rise and fall in direct step with engine rpms as the oil pump is mechanically driven.

The rule-of-thumb for good acceptable oil pressure is 10 psi per 1000 engine rpms so your 20 psi at idle rpms is more than fine.
 
If you raise the revs and the oil pressure goes up to 50psi then your oil pump is working. You may have bought a TJ with oil presser sender fault. if you are reading 20psi at idol and it raises with revs then its fine. below 15 is not so good and zero on a working engine without eventual bearing knock is a sender fault.

Thanks for the reply. Yeah I thought the sender as well. I already replaced it and the issue is still there. Good while driving but pressure slowly drops while idling. As far as I know thats not normal right? It should hold a steady pressure at idle?
 
No worries, your oil pressure is fine and it is supposed to rise and fall in direct step with engine rpms as the oil pump is mechanically driven.

The rule-of-thumb for good acceptable oil pressure is 10 psi per 1000 rpms so your 20 psi at idle rpms is more than fine.

Ok good to hear. All keep an eye on its for now. I owned this the same year jeep a while back and dont remember the pressure dropping while at idle. For now Ill treat ot as a watch and see. Thanks
 
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Reactions: Jerry Bransford
I have the same IPC readings at low rpm. My problem started after replacing the sending switch. Old one leaked so figured why not, new issue. I che ked my actual base pressure with a tool and it's fine. So yea, out of spec switch likely if you have no engine noise.
 
Non-OEM sender units are a crapshoot. If you're really worried about it put a mechanical gauge on it, but it's pretty unlikely you actually have an issue.
 
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Reactions: Woodrow
No worries, your oil pressure is fine and it is supposed to rise and fall in direct step with engine rpms as the oil pump is mechanically driven.

The rule-of-thumb for good acceptable oil pressure is 10 psi per 1000 engine rpms so your 20 psi at idle rpms is more than fine.

Jerry - what year did Jeep start using the dummy oil pressure gauge?
 
I don't know the year, but if you have numbers on the gauge, it's a real one. If you have L and H, dummy.

The dummy gauge is a real one too. It just doesn't give you useless readings at every speed. I rarely even look at my speedometer, why would I want to stare at the oil pressure needle too? 🤫
 
The dummy gauge is a real one too. It just doesn't give you useless readings at every speed. I rarely even look at my speedometer, why would I want to stare at the oil pressure needle too? 🤫
X2, it's legit. If the real underlying oil pressures are within the acceptable factory ranges it shows mid-scale. If they're not the oil pressure gauge indicator will drop and indicate a problem. I'd prefer my '04 showed the actual oil pressure like my '97 did but it doesn't and I don't lose any sleep over it.
 
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Reactions: TheBoogieman
X2, it's legit. If the real underlying oil pressures are within the acceptable factory ranges it shows mid-scale. If they're not the oil pressure gauge indicator will drop and indicate a problem. I'd prefer my '04 showed the actual oil pressure like my '97 did but it doesn't and I don't lose any sleep over it.

My '04 has the L-H gauge as well.

Anyone know if it's the gauge that's make the "translation" or the ECU? I'm running a dodge ECU on the Hemi, but I run that factory gauge - which seems to work OK. Until this thread, I've not thought much about it.