After the swap of the cluster. I learned the oil pressure was 30psi while driving and 15psi at stop light. Low. I did some reading and found it could be the oil pressure sensor. It was! It is located next to the oil filter. Easy to replace from engine bay. All that is needed is a wrench. Easy access. Cost was $25 @ O'Rilley. Part # : 2-8197. Now oil pressure is 55psi while driving and 40psi at light. Much better!

I hope this info helps someone.

 

I would hate to bust your bubble but are you sure this new one is reading correctly? And that the old one wasn't reading correctly?

I only ask because I have used a brand new oil pressure sender that was faulty right out of the box.

Did you verify it with a mechanical gauge?

 

I only went off what my last Jeep 4.0 read with a rebuilt motor I had done. So, were good My posting should be close to specs. But, I am all ears if someone actually has a different reading. Until then, I am good with the results.

 

Mine is 20 at idle and 60 with my foot on the gas. I'm pretty sure I've read many different times that that is what you should want. But if your gauge is reading correctly than you are good to go.

 

40 psi at light engine warm sounds little high....jm2cw

 

ditto 20 and 50 here but im 89 and 199,000

 

Yeah I was thinking the same thing

 

This keeps coming up off and on. Does anyone know what is the acceptable range according to ChryCo.?

 

Great question.

My '93 YJ with 188k and rebuilt top end was 60psi while driving and 40psi at light.

My '97 XJ with 130k is 55psi while driving and 40psi at light.

My '02 Suburban with 5.3L is 60psi while driving at 40psi at stop light.

Pretty close! I have text 4 friends with same motor, even son-in-law with daughters new Jeep JK to see what their is reading with a brand new motor. Will update soon.

 

According to the factory service manual for my '98:

4.0 specifications:

At Idle Speed (600 rpm) - 13 psi
At 1600 rpm and higher - 37-75 psi

I would assume that most, if not all later 4.0 models would be somewhere close to those figures. Earlier models may be different, depending on their specific pumps, and spec'd bearing clearances.

My XJ has a remanufactured ATK longblock in it with about 8000 miles on it right now. I get (based on the tick marks on the dash gauge) about 10-12 psi at idle, and 42-45 at anything over 1600 rpm. No ticking or other frightening engine noises.

I believe that at some point (and not necessarily on Jeeps of any kind), either some sending units and/or gauges may have been equipped with resistors that caused the gauges to always read at least 40 psi. I have heard this was done by the auto industry because it freaked people out to see the big swings in pressure. I can tell you that my '02 TJ 4.0 always read at least 40, no matter what time of year, what viscocity of oil, or how hot or cold the engine and/or oil was. It may have read higher at throttle, but it never, ever, read below 40 PSI.

 

I am a little old school, but I thought I was always taught 20psi is dangerously low. With the last 35+ cars I have owned in the past few decades, 40psi is pretty normal. Thanks for the confirmation.

 

Thanks for he input. But the resistor idea would really defeat the purpose of having a gauge, right?

 

Sold Jeep YJ. But, did find a pic of the guages. This was taken in August. 115* outside! 180* state (with 1/8" drilled hole), and severe duty Hayden fan clutch. I also upgraded the fan blade count for more air to blow on motor. The dealer at the time offered it as an upgrade. 5 blade to 7 blade. She ran cool!

Anyway, the oil pressure is above 40pis at idle. This was taken maybe 2yrs ago.

 

I agree that anything below 20 psi makes my butt pucker a bit, but right there in the FSM it says 13 psi. It freaked me out at first, especially given what i was used to seeing with my TJ. But thus far I've had no problems, even in Texas heat.

From what I understand, the resistor doesn't completely negate the function of the gauge. It just keeps it from going below a certain point that is deemed "acceptable". The gauge can always go up in psi, but the resistor effectively changes its bottoming-out point to 40.

 

there old school formula for every 100 rpm should be 1psi at idle ..this is very minimum acceptable ...