what could it be?it seems to run fine.

 

My concern would be that you have a genuine fluctuating oil pressure (as indicated by the gauge) – either due to a pump fault or some form of relief valve operation/sticking.

It could be an electrical fault (in the gauge circuit) causing the fluctuating readings.

Given the importance of engine lubrication – I would get it checked out before you have a very expensive repair on your hands.

Any garage worth its salt should have the ability to determine whether the engine oil pressure is acting up.

 

Or, replace the Pressure sending unit. Pay attention to the oil pressure once you do to determine if the pump is going bad.

 

what year cherokee? the earlier renix models (86-90 i believe) had many electrical short comings one of which is a poor ground connection for the gauge cluster, the poor ground could cause false readings. If it is one of these models i can give you a way to improve this ground. also even if this turns out not to be the problem it would be good to do anyway.

 

2000 and newer do not have oil pressure gages....that thing that on the dash is useless.
The oil sending unit is just a simple pressure switch that closes when pressure is above 5-7 psi and moves the gage to mid scale. when pressure drops below 5-7 psi gage will go to zero.....those are the only two positions the gage will ever display!

 

WHAT??, my 2001 GC Laredo has an Oil Pressure gauge. What are you driving?

 

'04 GC

 

My mistake...it is '03 and newer that don't have oil pressure gages.....it looks like a gage but it ain't no gage, it is fake!

 

Now that is a damn shame!!

 

HAHA!!! I was looking to change my oil pressure sender in my 04 because I thought it was broken! Why oh why would they make the gauge a fake!?!?

Question.... Is it possible to change the sending unit to one that actually means something? Or will the computer not know how to read the sensor correctly and show all kinda crazy readings?

 

Good question but I do not think the computer is programmed fo an analog signal. The '04 sending unit is just a simple switch that closes and grounds the computer input when pressure is > 7 psi.