Low oil pressure at idle?

[RJK]

Hey folks, I don't know if this is normal behavior, but I recently noticed that my 1972 240Z will show an oil pressure at idle of basically zero. In any gear, as soon as I give it some throttle, the oil pressure rises predictably to a "normal" range. Hold it at 3500-4000RPM for 5-10 seconds, and the oil pressure will rise to 50-70PSI. I did some recent wiring/ignition work, so I'm not sure if this recently manifested itself, or if I somehow didn't notice it for all these years. Is this normal, or concerning in any way? I would expect the oil pressure to drop at idle, but this is literally to zero. Seems strange. (side note: since installing an MSD 6A ignition box, I am having some strange gauge behaviors, at least at the tach.....what reads as 2k is absolutely not 2k-there's maybe a 500-700RPM "offset".)

[DatsunZGuy]

These cars typically have low oil pressure at idle.  If in doubt, get a new sending unit.  They are some of the last affordable replacement items left in the engine bay.

[Patcon]

or just check it with a mechanical gauge. I don't trust any of the senders

[siteunseen]

You might pull the valve cover and check the spray bar too. It could be loose somewhere and dropping oil instead of spraying through the small holes. Simple reassurance to me if you haven't checked it lately. Then again there's always the quicker way of removing the fill cap while it's idling and looking at the oil sling around. Mine almost jumps out of the hole so it's a pretty good amount flying around in there even at idle.

[mailnome]

Where is a good spot to hook up a mechanical gauge? I guess right there at the sender?

I vote for the sender unit too, I think they eventually have a hard time registering low pressure.


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[Racer X]

46 minutes ago, mailnome said:

Where is a good spot to hook up a mechanical gauge? I guess right there at the sender?

I vote for the sender unit too, I think they eventually have a hard time registering low pressure.


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You can put a tee in the block where the sender goes, screw the sender in one port, a mechanical gage in the other.

The rule of thumb for oil pressure is 1lb for every 100rpm. So at idle if you have 10lbs you're good to go.

 

[RJK]

thanks folks!!!