Just bought an 86 Cherokee 2.8 and oil pressure readings seem weird.

I've just read all the postings covering low oil pressure. (A lot of
postings.) The sender often seems be the prime suspect.

When I first start the engine the gauge shows about 40 pounds and
drops to about zero before there's even much heat in the engine. It
stays there if I run the rpm up to 3500 or so. No warning light comes
on. There are no rod or lifter rattles or knocks that I can hear.
Nothing that sounds like main bearing "clunks" either.

Odometer says about 165k. Seller says it has only been started every
couple of months for about 1+ years. Hasn't been driven because of the
oft mentioned black smoke,stumbling throttle response, rough idle
thingie, whatever that is. She claims no history of low oil pressure
problems. Oil was down a quart and dirty when first checked.

I'm afraid to drive this thing home.

Suggestions?

Thanks,

Lance Ferguson