I have installed a gauge, about a year ago,It is a vdo works great. Just recently my oil pressure dropped from 60 to about 20. When i first start the car green light stays on for about a minute. I don't hear any loud knocking so I know it is getting oil. After that the pressure goes up to about 10 psi. When i drive it the pressure goes up to 20 to30 psi. It does not fluctuate much. Yesterday i changed the oil and when i first started the car the pressure quickly went up to about 40 psi. When i took the car off the stands and started it was back to 10 psi. I don't think it is the gauge,ideas? could it be oil pump? When i drove the car it ran really well. No loud engine noise. Oil temps are normal.

Sender?

If it were me, I wouldn't drive it until I found out what was going on.

Clean out your sender and see if that makes any difference... and also make sure you have good wire connections on the sender. I had a similar issue with my car but it
was a consistent sluggish reading on my gauge. It would take about 15 seconds for the gauge to read the oil and the idiot light would stay on. It turned out to be some
debris in the sender. Yours sounds more like wiring to me though....

Sender ground? Maybe, weird things happen with bad grounds.
Pick up tube? Maybe, higher pressure on jack stands is suspicious.
Bad sender? Maybe, clean it first.
Oil Pump? Not likely but maybe, self machining would have other consequences.

what is the motor history
I would verify the guage, but it could also be a worn motor
doesn't sound good

you might want to take the old oil filter and tear it open.(don't use a saw that leaves debris)

I have one pressure guage on the end of a hose, that I can screw directly into the motor oil pressure spot and measure pressure direct for testing (good for elimating all questions about wiring)

Good advice. I keep one in my garage. Always use it for rebuilds. Too damned important to trust electrical gages/senders.

This doesn't sound good. When did this start? With this info, looks like your gauge is reading ok. What is the oil level at?

I took the sender out and checked it out looks ok oil in tube running to it. When i hooked it up again no oil pressure Im thinking it is the sender at fault.

Any way to test the sender?

I would be very afraid to run the car at this time

I would buy a mechanical guage that you can thread into the stock location for testing purposes....

just because you don't have rod knock, does not mean you have oil pressure

do you still have the stock single pole sending unit
you might see if that changes the green stock warning light.
you can pull all of the plugs and run that test by just cranking the motor with the starter enough to build 3psi.

the case is NPT
buy a brass tube of the same size that you can screw in rigid for static testing purposes.... bring that up to a brass block that a mechanical oil pressure guage can screw into...
(or you can use a flexible hydraulic hose if you want)

but I would run the mechanical test first
then if you have pressure then replace your sender...

brant

Could be no ground at the sender. If you used teflon tape on it, may not be grounded any more. Try connecting a ground witr to the sender, hole the wire in place with a hose clamp. Only need to ground the body.

Problem solved it was a clogged feeder tube.When i installed the sensor i used a grease gun hose. I used a piece of wire stripped and ran it down the hose. After that it worked fine. Thanks every body.