Help why would my oil pressure be so low?

 

Weak oil pump.. worn cam bearings.. pressure gauge/sending unit inaccurate.. oh wait, make that last one first

 

If you have an oil pressure gauge, read it while driving. But don't crash, haha.
On a cold engine:
-40psi at idle
-60psi under acceleration
On a warm engine:
-20psi at idle
-30 to 40psi under acceleration
The pressure can also vary because of the viscosity of the oil you use. I use 10w-30 and I have no problems. When was the last time you changed your oil and filter? If it's been a while, do it again and see what happens. It's periodic maintenance anyway.

 

Sorry, 10w-40. I had a typo.

 

This. kjc nailed it.

Low is a subjective term. What are your ACTUAL readings? The oil pressure spec for the 4.0 is as follows. If you are within these specs, you're fine.

*Not less than 13 psi at hot idle
*Between 37-75 psi over 1600 rpms

For truly low oil pressure readings, you can start with one of two things.

1. Get a "mechanical" oil pressure gauge. Temporarily install it where the oil pressure sending unit resides. Then you'll know for sure.

2. Take a chance that the sending unit is the culprit and get a new one. Buy a MOPAR unit from a Jeep dealer for best reliability/accuracy/mating with your factory unit.

 

Read this while you're at it:



http://www.jeepforum.com/forum/f19/4...fixed-1304679/

 

Thanks for all the help guys! Since ive had this xj its had just the lights and not the full gauge cluster untill yesterday i installed a full cluster yesterday and the oil pressure drops to 0 while idling and i notice the smoke coming from the tail pipe looked blue.

 

Blue smoke at idle could be valve stem seals. They can be replaced easily without removing the engine. Perhaps you should test the oil pressure with a mechanical gauge before proceeding. Did you read the link I posted above?

 

Not yet ive got a house full of kids tonight i will when they go to bed .. also im waiting to get a new compression tester!

 

ok so if previous owner was bad about oil changes there is a filter on your oil pump most likely it is clogged up so BEFORE you buy an oil pump take your old one off more than likely it will be clogged you can get the oil pan off from underneath if you take the steering crossmember and sway bar loose but you will have to jack the axel back up when putting the sway bar back on oh and you will have to shake the oil pan to get it out. i have just done this with my jeep and it will take about a whole days work with a lift so dont take it to a machanic or ull be looking at alot of money spent

 

Ok thanks

 

Thats a very good idea! never would have thought about that!