Problem started with oil light flickering, found oil was low, but still between ADD and FULL. Added some oil and brought it up to FULL. Went on my way, and after another 10 minutes the oil pressure light again flickered.

Got home and the next day (cold) screwed in a mechanical gauge and started the engine and the pressure slowly rose up to 15 but stayed there ragardless of RPM, Restarted the engine and now the pressure goes to 20 and then varies with RPM up to 50 at 3000RPM.

Have tried this on 3 different days with engine cold and swapped in a 2nd mechanical gauge. Always the same result.

The engine has always been run on synthetic oil so I would not suspect sludge or varnish.

Has anyone come across this before?

 

Oil pressure sending unit perhaps??

 

I'm a little confused. You say on a restart you got 20-50 up to 3K rpm, nothing wrong with that. Are you still getting the 20-50 psi with the mechanical gauge? How was your engine temp?

 

I agree nothing wrong with oil pressure of 20 -50 (50lbs at 3000RPM). However thats not the way it is when I start it cold. With a cold start it goes to 15 and stays there regardless of RPM. Granted the oil pressure of 15 was with a mechanical gauge inserted and with no driving. But it sure seems something is odd that if I start and run car for 1 minute and the oil presure is one thing, then restart the car and its different.

It sure could be the oil pressure switch, but I would like to better understand the odd oil pressure at startup before I replace the switch. Maybe the odd oil pressure has always been there and I just noticed it when I attached a mechanical gauge.

I have also tried a second mechanical gauge, with same result.

 

I agree this is a little perplexing. On cold start-up you should get higher pressure at lower rpm's as the oil is thicker and offers more resistance to flow. Remember, pressure is the measure of flow resistance. There is a pressure control valve in the system which bleeds off excess flow to limit pressure. I would think it is at or near the oil pump. This valve may be bleeding off when cold and working properly when warm??? Theremay be a by-pass in the oil filter but I would think that it would not affect system pressure. You may want to replace the oil filter (cheap try) and see if you get any better cold start pressure. Where in the system is the oil pressure sender? If the pump is worn you wouldget good pressure (less leakage) when cold and lower pressurewhen hot. How did you hook up the mechanical gauge? Did you remove the oil sender switch first or attach it in line with the switch?

 

Does the oil pan look like it is smashed or dented at all? Possible the pan is up against the sump pickup or the screen is plugged.
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