m103 has 0 oil pressure at idle
 

About 1 mile from home I notice the low oil light. I also notice that I have 0 oil pressure at idle but 3+ at around 1500 rpm. Car usually takes a quart between OC. I add 1 quart and that brings it up to 1/2 quart low. Start it and still 0 pressure at idle and 3+ with just gunning it a little. I go for a short drive and still 0 pressure at idle. I'm thinking (hoping) something happened to the level sending unit or the oil pressure switch. Any thoughts?

3+ PSI or 3+ Bar ?

If Bar, the sender is likely bad. If the oil pressure relief was stuck open , pressure would likely still be low at 1,500 R.

Do you have an external oil pressure gauge available to test with?

just to clarify. You mean the oil level sender and NOT the pressure switch? It's 3+ bar (full max)

I had the same problem and said OH NO! (Thinking oil pump went out...)

So I removed the oil filler cap and peeked inside the engine with it running. Plenty of oil flowing to lubricate everything!

So the oil pressure sending unit was a LIAR! I replaced it and it now indicates oil pressure at idle - low like 1 or so when warm, but no longer 0. And it goes up to 3 when I am driving.

I'm talking about the oil pressure sender.

Oil pressure sender