And the warm numbers are? Are cold numbers in the 45 PSI range idle and 2000 rpm?

Spec for D2 is 10 or above idle, and 50 hot at 2000 rpm. When cold, typically you will read about equal for both idle and 2000 because bypass valve in filter is active, no flow thru the filter material, and oil is thicker. As it warms up, bypass valve closes, and the idle pressure is reduced.

D1 3.9 liter spec is 40 PSI at 2500 rpm warm.

D1 4.0 liter spec is 30-40 PSI at 2500 rpm warm.

 

Yes sorry, meant to post the rest but got distracted by a work call. Cold idle was around 43 PSI and at 2000 rpm went to what looked like 45.5/46 PSI (again the it's a cheap gauge that is only in increments of 5 so I think I might go buy a nicer one to install). When the truck was at running temp the PSI was around 20/21 idle and jumped up to just above 50 PSI on the gauge at 2000 rpm. I have a T joint and am going to install the mechanical gauge so I can see what the actual PSI is. Does anyone know where I can get as close to an OEM mount as possible for the gauge? Was at Pep-boys and Auto Zone and wasn't too impressed by what they had.

Again thanks everyone for your help.

 

Well, an OEM mount for an oil pressure gauge comes in a big box marked "complete knock down" Series Rover.... they actually had a factory option for an oil PSI gauge in the dark ages before Disco. So you are own your own to be creative of the Disco, some have posted photos of pods that attach to the windshield post, etc. Even saw one pix somewhere of one mounted under the hood, so he could check it with everything else on the fluids check.

You pressure sounds spot on. A cracked oil pump would have a hard time making that good a pressure.

But why the low oil warning? Trash on the pickup screen? Pickup tube about to fall off? Pickup tube O - ring toast? Bad oil PSI switch? Rubbed insulation allowing wire to ground out somewhere (no likely if it goes away at speed and does not come on at other times)? You may sleep better if you drop the pan.

 

I have added it to the list of things to do, I don't believe there was an actual drop in oil pressure. I believe the sender switch is faulty or the connection was dirty, I gave it a good cleaning before putting it back on. I have a new one arriving on Wednesday and will install it then.

Plus I have the mechanical gauge hooked up via a T joint and I have it temporarily sitting under my dash (ghetto I know, but I want to monitor the pressure to doubly make sure it's just the sender switch).