Oil Pressure Woes?...

[EricB]

'81 F54 L28 rebuilt 3000miles ago with new bearings/rings

Also has MSA cast Al oil pan with 7qt capacity

L28 oil pump fitted with stiffer comp springs

Changed the oil friday morning before I set out on my 1200mile weekend up to Monterey, then San Francisco, then ..., etc returning back to LA last night

On the drive up no problems of course

Last night somewhere in the middle of the valley on the I5 cruising at a steady 4000rpm in fifth (roughly 80-90mph) i notice that my factory oil press gauge which reads usually somewhere between 45-55psi (ie the needle over the "L" of OIL) is actually hovering over the "O" so I am guessing that puts it at a pressure of roughly 25-30psi

I pulled over at the first gas station, let it sit, checked the oil, checked the oil again... still nice and clear and still at full level... checked all over the engine saw nothing wrong

gingerly got back on the road....

the oil pressure seemed to be better just coming out of the gas station and getting on the freeway, but once cruising again it settled back to the low reading i observed earlier... i also noticed that if i gently accelerated from 4000rpm in fifth gear if the oil press needle did anything at all it would slightly drop further, not increase... wtf???

sweated bullets up & over the grapevine but got home a-ok

am changing the oil & filter again this am, will go around the block again and do some other testing of the sort... but i may just pull the engine this weekend and go look inside...

what do you all think?

-e

[ChrisA]

Hey Eric, this a bad way to check things. With the engine idling, take the oil fill cap off and look in with a flash light, you should see oil squirting out lubing the rocker arm cam contact area.

I have a secondary mechanical oil pressure gauge plumbed in at the electric pressure sender on my 73. It sounds to me like your sending unit is going bad.

Much luck,

Chris

[240ZX]

If what Chris said does not apply, then I would ask if you replaced your oil pump when you did your engine overhaul?

[26th-Z]

I would have the same thought, Eric. Especially before I went to the trouble of pulling the engine out.

[240ZX]

I would have the same thought, Eric. Especially before I went to the trouble of pulling the engine out.

Who said anything about pulling an engine?

26th, are you trying to stir thinks up here? :laugh:

[beandip]

Dont use a after market sending unit bite the bullet and go to Nissan. you wont be sorry.

[sblake01]

Who said anything about pulling an engine?

[/quote=EricB]... but I may just pull the engine this weekend and go look inside...

Eric B did! Don't do it! Check the sending unit and guage first.

[Victor Laury]

Eric. Swap sending units with me and see what changes on both cars.

[26th-Z]

What???? He said; "but i may just pull the engine this weekend and go look inside..." and then ChrisA suggested looking at the cam to determine flow and then suggested checking with a mechanical gauge. All I did was agree. WTF? Stirring it up? Is that what you guys think of me? Geez. I'll sit down and shut up!

[Bambikiller240]

"Chill pills for sale, get your ice cold Chill pills. Two for a dollar."LOL

I think 240ZX just misread the earlier (original) post, or didn't read it carefully.

[26th-Z]

Mr. Stir-it-up here.

[ChrisA]

My 72 with the L28 is notorious for showing good oil pressure(on the gauge) for about 30 minutes after startup then slowly decreasing. I'm sure its got something to do with a combination of the sending unit being not all that accurate (new Nissan part when L28 went in) and the oil changing its physical properties as it absorbs more and more heat. Could the constant voltage through the gauge cause some drop off in the reading over time? The windings in the gauge itself have to be degraded on a 32 year old car.

FWIW

Chris