Verifying Oil Pressure

On and off Ive been working on my wifes grandpas Mitsubishi Satoh Beaver tractor. Its a cute little 2 cylinder diesel. Its been sitting for 20 years and I just now got it running for 15 seconds or so before letting it die. Problem is the oil idiot light stayed on. I figure itll take a little while to prime up but would like to verify its pumping before I start it up again. Does anyone have any ideas on how to check this? I was thinking about pulling the oil filter to see if it was filling up at least.

Im presume u checked the oil in it. Find an oil f as Lowry plug and remove it. Then crank it or just enough to start and stop it and oil should be flying out. Or did I change the oil in it ? Then it would take a few seconds for it to go out. Could check filter also.

In the attached picture number 9 is the oil pressure sender.
You could screw it loose to see if there is pressure there when you start it. Ideally you should hook a manual gauge to it to see what is really going bad. Look at the gauge in the link, not sure what they charge for shipping but that is certainly cheap enough as a check gauge. The problem may be the engine could have metric threads, that would require an adapter. You may also be able to go to Oreiley or other parts stores and get a loaner test gauge there. If the circuits work like the majority of them if you unplug the wire off the sender and turn the key on if the light is out there is a good possibility the wiring and light is working correctly. It is then a matter of whether it actually has no oil pressure or is the sender bad. If the light stays on with it unhooked it possibly means the wire is shorting to ground somewhere between the sender and the light or the light is also connected to something else that has a problem and it is lighted to warn you about that. Do you have an operators manual it would probably tell you if that is the case. If you do not have one when you get my email you will have access to one. I may have to give an explanation of how to find it.

Manual Oil pressure gauge

Thanks for the comment and the email. Ill be checking out the forum link you sent.

It has fresh oil. I unplugged the sender unit wire and the light comes on and off as expected. Then I cracked the new oil filter loose and it was bone dry. Hoping that it just needs a little more run time since its been sitting so long but will start researching if theres a way to prime the pump

cranking the engine with the fuel shut off is probably the best way to prime the pump.

Go to page 2-32 in the manual I directed you to. I would pull that plug above and in front of the oil filled and dump oil in there. Look at 2-33 in the pump diagram above the one that shows the pressure switch. If that spring and ball are in there pull them out with a magnet. You should then be dumping the oil right into the pump. Once you get some oil in there I would think it would go ahead and prime itself.

Be careful what you screw into the oil pressure port, many foreign engines are BSP threads, similar to our NPT, but not the same! Whenever possible I always fill the filter with oil before installing it, if it screws on from the bottom.