#1:Low oil pressure.#2:digital dash

[driveshaft man]

New to the GN world so if my questions are better placed elsewhere ,please inform me. I just bought (from a broker)1986 GN.45k miles(?) looks good enough to be right, but who knows what this car has been thru.
Oil pressure at cold start1800 rpm @40 + psi . Hot idle drops to 10; if idle drops under 800(blip the throttle and almost dies before catching ) and pressure drops even more. Oil appears mid-life in change cycle. What is normal psi readings and what oil is recommended ?
Second , Digitial dash reads incorrect on fuel, assuming that display is gallons remaining in tank.(sender?)And there appears to be boxes under fuel reading that could be other displays but nothing ever lites up there. No one in my world has ever even seen this dash before so any help would be greatly aapreicated.
Harold

 

[boostingbuick]

Oil pressure at idle hot is normal at 10 psi. I don't agree with that but that is what gm states as normal. But you said it drops lower than that. I assume you mean just as it going to die and them catches itself? You may have a idle control motor going bad. Normal.

And as far as the fuel gauge goes, I would say that is the norm as well. Mine is that way. I know when it says I have 4 gallons left, its really means " tie up your laces". I just deal with it.

 

[driveshaft man]

I have learned a lot about the control systems by reading the posts made here.Thanks for the tip on the motor...I think I even know where it is.The gas gage is all over the place,showing 8 gal but would not start.Added a 5 gal can and now shows full . Is this fixable ?. Any other displays on dash besides gas,mph, and trip odometer?
Thanks,Harold

 

[bison]

What is your ol pressure at 2000rpm? How about 5000rpm? You need about 12 psi/1000 rpm and that is it. Usually be 2000 rpm its around 40 psi and hits a wall around 60 psi when hot with the factory relief spring. Anymore is not needed. The digital dash is not the problem. Its the sending unit in the tank. There is a metal arm and a resistor on the sending unit. It can be played with to get close to actual numbers but most are not that accurate. You should not get below 5 gallons actual fuel int he tank anyway so just be sure there is at least 5 gallons in there. You could pump out all the fuel and then add in 5 gallons and check the reading. Or you could replace or play with your current sender to try and get it close. You can check it out of the car with the key on. Unplug the ecm 12v wire by the battery (its the orange wire) to avoid being sprayed with residual fuel in the pump when turning the key on to check the sending unit with the sender out of the tank.

 

[turbofish38]

The sending unit in the tank might be gummed up or have some rust on it if the car was sitting for any period of time. It's normal for it to read a little off but not as off as the numbers you have stated. Probally what I would do for awhile is always fill the tank up to the filler neck and let the gas clean what rust and gunk that is on the inside. A couple of full tanks should get it reading a little more consistently anyway. Do a fuel pressure check or replace the fuel pump and at the same time you can clean the crud out of the bottom of the tank when the time comes.

 

[driveshaft man]

Oil pressure comes up quick with rpm, probadly 30-35 at 2000, haven't looked at 5000. Also don't know weight of oil in it now, but was going to Delo 15w40 when I changed. Happy to know problem is in sender , not dash . Maybe more work to solve but less money and won't have to send dash unit out for repair. I normally keep a gas tank full so hopefully this will correct itself on readout.It has a fuel pressure gage underhood that shows 30-35 at idle, which from what I've read , is normal for a basic stock unit.Thanks again for insite.Harold