oil pressure goes up to 30 on start up, but after about 15 seconds it slowly drops down to zero. i checked the wire from the pressure sending unit and it looks clean. any other thoughts where i should start

 

You have a few options here.

1. Ignore it
2. Use sandpaper and clean the terminal on the sender
3. Replace the sender
4. If oil pressure is important to you, get an aftermarket gauge

Keep in mind the stock oil pressure gauge isn't all that accurate or useful to begin with. I wouldn't stress over it all. I'm also assuming you're talking about an fd.

 

Profile lists a 87 rx7 gxl.

I like to see my oil pressure. You could have someone monitor the gauge while you manipulate that connection with the engine running. That would tell you if it's the connection or sender.

 

People like to pretend like these pumps never go bad.. Isn't true. If you rule everything else out by process of elimination, it very well could be the pump itself.

 

Pumps going bad are fairly rare on a n/a engine

My biggest question is what weight oil are you using and what are the temps outside right now?

 

I have had to replace the pump on more than one of my cars due to oil pressure acting as the OP described. The FC3S are 30 year old cars now. I wouldn't say it's nearly as rare as it once was. The first time I made a mistake assuming my gauge was simply faulty and wrote it off. This lead to a short lived engine that burned lots of oil due to excessively worn oil control ring carriers.

To the OP: If it's determined to truly be low pressure, go by the procedure in the FSM to check the pump clearances with the feeler gauges. you may be surprised how out of spec it is. Perfect time to upgrade to a turbo oil pump if you see fit.

 

5w30. 60s in the day and 20s at night.

 

thats a little thin, I'm on 20w-50 for around the same temps, and I got 30 hot idle, 60 going down the road

 

A 5w, especially with some fuel dilution and a dirty connection at the sender can all conspire to give low indicated oil pressure at hot idle.

 

^THIS, I forgot to add that, all rotaries get fuel dilution in the oil, and it doesn't help any with oil pressure

 

Mine is very finicky as well. Try replacing the sender and getting a new gauge if oil pressure is that important to you.

 

so now none of my gages work

 

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https://www.rx7club.com/3rd-generati...orking-754067/