No oil pressure at idle?

[Zedyone_kenobi]

The OEM guage is notorious for not reading accurate. I had a brand new datsunspirit engine installed in my Z and it was running great, but when I came to a stop it read very close to zero.

I bought a new sending unit, removed the crappy pigtail going to the sending unit. Cleaned and soldered all the connections. But prior to hooking everything back up, I hooked up a simple mechanical gage to it and it read 25 psi at idle fully warmed up with 10w30. So the OEM datsun gage read 0 or close to it, but a new autometer mechanical gage read 25. Do not get too worried. IF you must know, buy a simple mechanical gage and test it to give yourself some peace of mind. But I bet it is a combination of the sending unit combined with a crappy OEM gage.

[Captain_Zeros]

A bit of a tangent, but oil pressure is a lot less important than oil flow.

It's just a lot easier to measure. For a given amount of flow, adding restrictions will increase pressure and removing restrictions will decrease that pressure, as long as the dinosaur-juice is flowing it'll be lubricating. Your new oil filter is probably just more restrictive than your old one, or your new oil after changing the filter is a little thicker than the old stuff you drained out, Jenny. (either that or heaven forbid, you got some kind of minor blockage in an oil passage at the same time and that's increasing your pressure. Just being the devil's advocate, I think it's probably the filter or the oil.)

If I'm remembering right, this article has some pretty good breakdowns on oil dynamics: FerrariChat.com - FAQ: Motor Oil Articles by Dr. Ali E. Haas (AEHaas)

[bartsscooterservice]

The OEM guage is notorious for not reading accurate. QUOTE]

Uhm..it's Seiko, not bad at all. Mine still works after 42 years..

@ ninja: must be the oil pressure sender.

[Zedyone_kenobi]

I did not say it was nonfuncitonal, but after 42 years, it probably is not all that spot on any more. By the time we get these cars, lots of things have 'changed' since new.

[Big sam]

My gauge can give some fairly low readings as well.I'll get around to ordering a new sender one day. I have a mechanical gauge that I fit every so often and check the oil pressure under driving conditions. And so far it's been fine.

[AZ-240z]

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I had the same questions when I purchased my car from the dealer new. It is just the nature of the beast. My car, recently restored

to include a rebuild of the engine, is completely stock with the correct new gages and oil sender unit. At idle, the oil pressure goes to

a needle off the 0 mark. At cruise speed of 3600 RPM, the pressure reads approximately 45 PSI. This has been 100% normal for my car

for the last 42 years.

The page I have attached is from Wick Humble's book, "How To Restore Your Datsun Z-Car" by way of a reasoned explanation from

a professional.

This is not to say your car may not have other related issues, but only to shed light on a very common complaint from day one.

Dan

[olzed]

This engine has been running at idle (and an occasional rev to attract people) for hours at a time over the last two years, and has no gauge or sender, second hand oil, second hand filter, and undersize bearing shells with shims to take up the slack. Oil pump of unknown quality, and water in the oil.

It rattles momentarily until the oil flow gets going, then it is fine. The vid was taken a couple of years back, and since then it has been given a radiator, as well as some more cutting from the block, and other minor places.

Controlling the oil flow was the main problem. I don,t have a clue what any pressure might be, if any.

Brian.

[Captain_Zeros]

That's awesome!

[FastWoman]

Upgrading my oil filter from the crappy orange FRAM filter to the Tough Guard FRAM filter increased the oil pressure substantially.

Jenny, careful with those Fram filters! A tough guard filter is merely a crappy orange filter with grip paint. IMO, the best filter for a Z is a K&N. Here's a review of several filters with... er... very interesting commentary on the Fram. I can't say I disagree with anything he says, but I don't think I would have said it quite the same way.

[Big sam]

great video;)

[olzed]

Haha. Thanks Tim.

[Stanley]

Zero pressure = zero flow. The oil pressure gauge is after the filter so a clogged filter will reduce flow (and gauge oil pressure). That's why the filter has a bypass - so you still have some lubrication if the filter is clogged. And that's why your oil pressure at idle goes up when you change the oil and put a new filter (if you waited to long to change it).

My stock gauge shows a little over 1/4 when idling cold, a little under 1/4 idling hot, and a little over 1/2 for normal driving.