Hmm, well it could be the sending unit, the pump, or the rear main seal.yesterday my truck decided to start dropping oil pressure when i come to a stop and I was wondering what it could be? now let start with it's a 95 ram 1500 3.9l v6 OK from what i can tell when its cold its just fine! after it gets warm everytime i come to a stop the oil pressure drops and my oil light comes on and Before i replace the oil pump i want to know if that's the problem or if its the oil pressure sending unit please help!
The first thing to do is to rule out the rear main seal and the pump. In order to do this you're going to want to connect a mechanical oil pressure gauge to the engine and check the oil pressure, if it is very low then you basically ruled out the sending unit which means that would leave you with the rear main seal or pump. Now if the mechanical gauge reads fine then you can safely assume the sending unit has failed.
Ok with that all on the table their... You're going to want to first drive the truck around until the engine is all nice and warm then you can stop and connect the oil gauge where the sending unit screws in, this ways you get an accurate reading.
I ran into a similar issue where my oil pressure would drop but it wouldn't drop low enough to cause the light to come on, for me my problem was the rear main seal which was evident by the collection of oil on the bottom of the bell housing