No oil pressure.
 

I just did a motor swap on my 95. After the installation, I turn the key switch to on and the oil pressure guage will go up to 90. When I crank the car up to start it, its back at zero. The engine starts and sounds good. but no oil pressure...did i forget to connect something? is there a pin for the oil pressure guage that i miss? if i did, where can i find it?

It cannot show 90psi without the engine running. Is it the switch type? Probably connected wrong.

How can i tell if its a switch type? I don't think i've ever seen whats behind the cluster. where can i find the connection?

Alright, let me think if I can drag out the memories of the various oil pressure senders... (somebody correct whatever information I fuck up):

The 90-94 senders showed higher pressure as resistance decreased. Meaning that gunk on the connectors or whatever would cause a lower reading than you should see.

The 95+ "fake" sending units were an on/off switch that operated such that when you hooked it up to an earlier gauge, the gauge would show to the max on the scale with no pressure, but somewhere in the middle (or maybe the bottom) with pressure above 7psi. This sounds like your symptoms.

Basically, I don't know what sender you have on the engine, and what gauge you have in the car, and therefore can't say anything intelligent. Did the "fake" gauges have markings for actual pressures? Did a '95 have a "real" gauge or a "fake" gauge (I thought '94 was the last year, but I'm not sure) and did you retrofit something else? Methinks that your problem isn't a lack of oil pressure, it's a hodgepodge of bastardized components that don't know how to play nicely together.

Wish I could be more helpful, but I haven't been thinking about Miatas much lately. I also can't help you identify one sender or another- but what year motor did you put in and did you use the sender on that motor?

Is your sender more the size of a quarter or a light bulb?

Let's put a picture into play, look above your oil filter but under the intake manifold, does the sender look like the one on the left or the one on the right?

http://www.too-many-parts.com/rs/ima...fore-after.jpg

the oil pressure guage on a 95 miata will show half way up when there is no oil in the car ,, WTF.. i think its just the diffrence in the year you got i would not worry about it much just make she checks her oil...

it looks like the one on the left

it looks like the one on the left with the pin.

You either need to swap to the gimp sender that you can get for $5 at autozone, or you need to upgrade your gauge to the old "true analog" style