hey guys i need some help with my 92xj 4.0 high output with 230xxx miles my oil pressure reads at about 20 but normally it ran at 40+ and i can't figure out why its so low? when i punch on the throttle it gains 10 to 15 but once its back idle again it goes back down to 20?
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92xj 4.0 H/O oil pressure?
- Thread starter Aliendu4
- Start date
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Oil pressure, as a general rule, should be 10 psi per 1000 rpm. Some references say 13 psi minimum at idle.
Put a mechanical gauge on it to see what it is really running at. Could be a failing sender or the wire where it attaches to the sender.
Gotta ask: what brand oil filter? What viscosity oil?
Put a mechanical gauge on it to see what it is really running at. Could be a failing sender or the wire where it attaches to the sender.
Gotta ask: what brand oil filter? What viscosity oil?
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Ok. Oil viscosity is correct.
Do a search on here for fram filters. They are controversial, but you should make up your own mind.
Do a search on here for fram filters. They are controversial, but you should make up your own mind.
iwannadie
NAXJA Forum User
- Location
- Gilbert, Az
Can you recommend a good mechanical gauge, or are they all pretty much equals? I keep meaning to pick one up for testing but never know what kind to buy or what/if any adapters are needed...
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Not high tech, you could get one from Harbor Freight to do the job. It needs to fit where the oil pressure sender goes, sorry, I don't remember the size, but most come with an assortment.
You could rent one from a parts store just for a quickie test.
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Well, I only use NEW pumps. Kind of like without a good pump it is meltdown time.
Some things you can go cheap. I don't put waterpumps, thermostats, radiators, clutches, brakes, bearings, and pumps (oil or fuel) in the "Go Cheap" category.
And I NEVER go cheap on customer's vehicles, only my own. Every mechanic/technician/shop owner I have ever known that went cheap on parts has lived to regret it. They have either gone out of business for come backs (freebies that always cost more than if the job had been done right the first time), bad reputations, or law suits. I have lost a lot of jobs to the "guy down the street" because he was cheaper, but that "guy down the street" isn't there for very long.
birchlakeXJ
NAXJA Forum User
- Location
- Melrose, MN
Hold up. I'm not at all sure you have a problem. What you describe, 20 psi at idle, is well within the factory spec. for oil pressure on the 4.0 The Jeep spec is at least 13 psi at hot idle.
In fact, my 99 has been at just a smidgen over 20 psi at hot idle since the day I drove it off the lot 10 years ago. I would be very hesitant to assume you have a problem with 20 psi.
If you are really unsure and want to verify oil pressure, then as mentioned, temporarily hook up a mechanical oil pressure gauge where the oil pressure sending unit currently resides. Mechanical gauges can be rented for a few bucks from many parts stores.
Oil pressure sending units have been known to fail on the 4.0 Verification with a mechanical gauge will tell the real story. And if it truly is 20 psi at hot idle, you are just fine. Digging in may be of no value and only expense.
hello I have a 92 4.0L with 161,000 at start up its right at 80 after warm its at 40 around town if I drive hard on the inter state and pull up on the ramp and cluch it it drops to about 25 for a fu sec.As soon as I drive off its back up to 35 to 40 I have checked it with a manal gauge to make sure and my dash gauge is verry close. i do lose oil presser with fram filters about 10 to 15 lbs all around. I run wix filters and Mobil Delvac 1300 super 10w30.
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Cheap part, no harm no foul.
Beg, borrow, rent, or steal(?) a mechanical pressure gauge and see what your actual pressure is. You could have a bad sender. Get the gauge.
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
It comes off of the Oil Filter Adapter, where the filter is mounted.
