Hello I have a 2000 Xj I put in a new oil pressure sending unit and my gauge still goes to zero when at an idle anyone else have this problem and got it fixed it is pumping oil

 

aftermarket or mopar oil sender? mine would drop to zero when it got ran hard and dropped to idle. Put in a mopar oil pressure sender and it never read lower than 20psi. Later when I changed my rear main, I also changed the oil pump and got no appreciable gains, but I was there and it was cheap. Unfortunately most of the time if it isnt the sending unit, its the cam and main bearings. oil pumps create volume, bearing clearance creates pressure.

 

I just battled with this for a few days.

I found a break in the ground wire at the sender. (pin 3)

You could not tell easily, had to ring out the harness.

 

Good advice on the wiring!

While you're at it, spend $15-20 bucks on a mechanical gauge from your local parts store. I picked up a Bosch for $17 at Autozone when this happened to me. Turns out my pressure was just fine - it was the sending unit. It's really common.

I just used it as a test without installing it permanently. I just removed my sending unit, connected the mechanical gauge, and took some readings. 40 at idle, 60 at 2100 rpm. Not bad for an engine with ~260k on it.

This took all of... 10 minutes, tops. Brain-dead easy.


Now I have a mechanical gauge around for testing any of my vehicles. Glad I did it.

 

I don't know how simular the newer Cherokees are compared to my 89 but my oil pressure was never reading. The gauge was up all the way past 80. In pulled my cluster and looked at all th connections for each gauge and dremmeld the corrosion off. Works spot on now. Same with coolant temp Volts. And my fuel gauge doesn't float around now.