Destro

Changed the oil and now I am showing no oil pressure. It was reading low before, but I figured that was due to the thin oil (needed an oil change when I got it). 6 quarts of new oil so I know it isn't a lack of oil. I will check and see if I bumped the sending unit, I believe it is near the oil filter- I may have bumped it. Should I get an oil pressure tester and verify actual oil pressure? I see them on E-Bay for $10- not too bad.

littleblueman

It sounds like you broke the sending unit. I did the same thing last oil change, as the old one had been hit a few times. My pressure was showing a little low before so it needed changing anyways. New oil pressure switch and the pressure is back showing normal. Cost me 32 bucks at Oreillys.

Destro

That is what I am hoping, but I may see if I can rent or buy a cheap oil pressure tester. My check engine light never came on, even with the gauge reading 0. The CE light does work as it comes on with the key for a second...

Also my washer fluid light is on, even after I filled it back up.

94HOCHEROKEE

What is standard Warm oil pressure supposed to be??? Mine will go from 40psi to like 82 when im downshifting to pass.

Firestorm500

No oil pressure = either bad/worn out bearings or bad oil pump.

New oil is thinner than old oil, therefore new oil does not fill the excessive bearing clearances. This causes the no oil pressure reading.

Drain about 2 quarts, put about 4 cans of STP in it, sell it.

Destro

Well I don't think just and oil change would drop oil pressure from 30PSI warm to zero, and it seems to run just fine still (no lifter noise or anything you would expect with zero oil pressure). I will track down a pressure tester and see, then tackle the problem from there- be it new pump or complete rebuild (stroker anyone?).

GreenClassic

Most likely the sending unit. You wouldn't get far without any oil pressure, the engine would seize up pretty quick.

Six-Pack Smile

what filter are you running because i have seen cheap one affect presure.

Destro

Fram Dual-Guard or something (the more expensive Fram filter). Well I drove it a couple miles without any knocking or any strange engine noises so I think it is the sending unit, but I am going to park it until I get my hands on an oil pressure tester. Going to try and pick one up tonight. This is the best price I have found for the sending unit:

$11.99 http://www.thepartsbin.com/catalog/?...294965190+5606

BuckB91XJ

Destro, the peace of mind knowing your oil pressure is good is definitely worth the cost of renting an external gauge, if not buying one. Sounds like the sender to me, too but, you can NEVER be too careful when it comes to verifying good oil pressure.

Destro

I hear that. I am going to pickup an oil pressure tester and sending unit tonight (if oil pressure doesn't test out I can return the sender).

If that fails it looks like I will try an oil pump. I was under the Jeep for the first time last night doing the oil change and it doesn't look too bad to pull the pan. Pump is only two bolts after that.

BuckB91XJ

Yeah, once you get the bolts out of the pan and the seal between the pan and the block broken. You can drop it just enough to get in there and remove the 2 oil pump bolts. This will make sliding the pan out much easier.

tkdtim

Not to derail, but on the flipside can you have too high of Oil Pressure?
Mines running 60-80.

Fraser

youd be suprised, im running 30w in mine and when it gets hot the pressure dives to nothin, and yes it is nothing. runs same as normal, no knocks yet or anything. I have since picked up another motor

Destro

I did the oil change and am only running 5W30 (what I had on hand) but only 5 quarts and one quart of STP oil treatment. From reading the oil pumps on the 4.0 is not very reliable so I am guessing that may be it if not the sending unit. Bearings are not as often the problem as the pump itself (crossing fingers). If it is bearings I'll probably just dump in some heavy straight weight oil and drive the crap out of it until winter when I can do a rebuild to a stroker. :-)

We will see tonight if I can get a tester for cheap or rent one... Ebay has them for $10 w/ $11 shipping! I think Harbor Freight has one for $9 I can go pickup today...