What's my oil pressure gauge telling me?

[garment]

Evening Pelicans:

My '83SC's oil pressure reading looks to be a bit wonky.

I am recalling the not too distant past (which means the 2 years and a bit since I owned the car, up to the start of this driving season here in DC) when the gauge basically read 1 bar for each 1,000 RPM. Now, I basically run at a bit higher than a constant 4 bar at anything over 1,500 RPM. Pressure falls to about 1 bar when idling and warm, which is what I would expect. The pressure on warm up looks to be more or less normal to me (3-4 bar until warm).

The car idles at a steady 900 or so. All stock. The only other clue was when the car was running hot, on a hot day in stop and go traffic this summer, with the oil temp gauge at about the 10 o'clock mark, pressure started to read as I would expect (1 bar for each 1,000 RPM). However, I've not observed that behavior since that super hot, super traffic-y day.

I've read threads that claim a constant pressure reading at 5 bar, which indicates a bad ground or bad sender, but I haven't seen this issue.

Any pressure reading gurus know what's going on here?

Thanks, Pelicans!

[Dave Colangelo]

What oil are you running/when is the last time you changed it. The temps have just dropped up here in the north east so you may be seeing a bit of that but I dont think it would change anything to drastically. Generally I see what you see 1 bar per 1200 RPM when cold and then between 1-2 bar once the car is warm. You may have an obstruction in your oil system, has the car been jacked up recently in a way that the oil lines could have been crushed? Checking and cleaning grounds is always a good idea when trouble shooting Porsche electronics in any capacity.

Regards
Dave

[Arne2]

Does it read zero with the key on but engine off?

Originally Posted by garment

The only other clue was when the car was running hot, on a hot day in stop and go traffic this summer, with the oil temp gauge at about the 10 o'clock mark, pressure started to read as I would expect (1 bar for each 1,000 RPM). However, I've not observed that behavior since that super hot, super traffic-y day.

My malfunctioning original sender would do that, read fairly high most of the time, and did not drop to zero with the key on but engine off. But if I got the oil good and hot, it would start reading normally. Once the oil cooled, it would go back to wonkiness. New sender fixed it.