another oil press question

[97XJ Jeeper]

ok had some low oil pressure issues so i did a oil and filter change. was using valvoline max life 10w30 switched to valvoline VR-1 racing 10w30 because it can handle high heat and switched from cheap champ filter to ac delco ph13. i think that is the right filter that what advanced auto cross refer for me. i also picked up a oil press sending unit good thing i hit the old one with a filter wrench and broke the plactic part off the unit. so i have good hot oil pressure now but it is slow to rise and fall is that normal for the 4.0. i drive some chevys and fords at work and there oil press gauge rise and fall fast like it was a boost gauge or something. could it be sludge around the pickup in the pan or the pickup screen getting clogged? i have good pressure now just wondering if everyone elses does the same.
:compwork:

[BGXJ]

i dont know from experience but i would think that the oil pressure would fluctuate rapidly only on startup and shutdown. Is that what you're referring to? Also, how much did that sending unit cost you?

[97XJ Jeeper]

i dont know from experience but i would think that the oil pressure would fluctuate rapidly only on startup and shutdown. Is that what you're referring to? Also, how much did that sending unit cost you?
it cost $25
no i am talking about when the rpms go up and down.

[XJPhoenix]

I think it's normal for Jeeps.

I've had old units, and new units, and they are all slow to react.

:)

[clunk]

yeah it's normal, around 10PSI pressure/1000RPM is what I have read is "perfectly normal".

[BGXJ]

mine doesnt work, always at 80

[97XJ Jeeper]

one more ???? i have a 97 if i want to use the bigger filter like the 5.0 ford filter do i need a thread adapter like i have seen in some other post? thanks!!

[XJ5]

No, the ford filter screws right on.

[Ecomike]

ok had some low oil pressure issues so i did a oil and filter change. was using valvoline max life 10w30 switched to valvoline VR-1 racing 10w30 because it can handle high heat and switched from cheap champ filter to ac delco ph13. i think that is the right filter that what advanced auto cross refer for me. i also picked up a oil press sending unit good thing i hit the old one with a filter wrench and broke the plactic part off the unit. so i have good hot oil pressure now but it is slow to rise and fall is that normal for the 4.0. i drive some chevys and fords at work and there oil press gauge rise and fall fast like it was a boost gauge or something. could it be sludge around the pickup in the pan or the pickup screen getting clogged? i have good pressure now just wondering if everyone elses does the same.
:compwork:

I recently changed the o'rings on my oil filter adapter and cleaned it up.....while doing so I noticed a build up of solidified sludge apx 1/8" thick/deep in the recessed area where the little steel tube coming out of the engine block and up to the adapter housing terminates with an opening of apx. 1/16". I suspect that tube leads to the oil pressure sender (just a logic guess on my part, maybe some one here can verify that???).

Based on the sludge I saw in that recessed area where the tube is located when the oil adapter is installed I suspect the inside of this tube also scales up with sludge over time, restricting the flow of oil to the oil pressure sender. That restriction could be slowing the pressure sensor response to changes in oil pressure. There could also be a pressure snubber (dampener) built into the oil pressure sensors themselves that slows the response to protect the sensor from pressure spikes.

Also, I believe the oil pressure sensor is on the clean filtered side of the oil filter, so a change in RPM might cause a delay in pressure changes on the clean side of the filter since the filter causes a flow restriction (pressure drop) that varies with RPM (and thus varies with pressure). When the RPM is raised (or lowered) suddenly, it takes a few seconds for the higher (or lower) oil pressure on the dirty side of the filter to build up (or drop) to a new equilibrium higher (or lower) pressure on the clean side of the filter where the oil pressure sensor reads the pressure.

Also the oil viscosity, and oil temperature (which affects the viscosity) would affect the flow rate through the filter to the oil pressure sensor.