low oil pressure?

[liltuber]

Hey everyone I'm new to the forum. I just picked up a 71 240z that has just had it's engine rebuilt, hasn't even been broken in yet. I was letting the car sit at idle before I adjusted the carborators when i glanced over and noticed that the oil pressure gauge was pegged at the bottom. I gave it a little gas and it raised to about 20. After letting off it soon returned to the bottom of the gauge. Also when i give it gas a small blue cloud is puffed out. The weird thing is, if i drive it around a little bit it will stop spilling out smoke. I can even let it sit after that and it still wont smoke. I pulled a couple plugs and there weren't any signs of oil, but it was running rich earlier so they were carbon black, but not wet/oily. I am hoping that this is just caused by the break in period and the rings haven't had a chance to seat yet. If anyone has anything to ad please do.(Checks I can do to make sure the pressure is fine, or anything else).

thanks

adam shepp

[240znz]

The oil sender on you block is probably shot. It is a common problem. You could try putting a new one on and see if the guage reads any better.

If it doesn't, then I'd be directing questions to the person who rebuilt the engine for you.

[DeesZ]

I agree with 240znz, likely a sender issue with the pressure. Just wondering, how did the pressure read before the rebuild? Do you have any way of finding that out? Assuming the sender wasn't changed out, your pressure should be about the same or better than it was. (Of course that also depends on what was wrong that required a rebuild in the first place.)

I'd consider speaking with the rebuilder now, not later. Get your issues documented real early, and see what the expectations are supposed to be for you (like am I to 'expect' the blue smoke for a period, should the oil he put in it be changed out at a specific time, etc.) Do you have any documentation related to what was done for this rebuild (top end w/ valve seals, bottom end, both)? Has the engine been run at all since the rebuild, or is your start-up the first since the work? Just curious, what oil are you running now? Also, is there any loss of coolant?

I hope this works its way out favirably for you.

[beandip]

DO NOT LET A BRAND NEW ENGINE SET AT IDLE !! maintain the RPM at or around 1500 RPM to keep the oil pressure and to lube the cylinder walls. Do not be concerned about a little oil smoke on a new engine . Drive the car as you plan on driving it all the time . Not a good idea to spin the engine up to high Rs when not under a load . I agree the oil sender cold be faulty , a common problem. I just went to the parts store and bought a cheep mechanical gage. I think it was less than $15.00 , connected it to the engine where sending unit is screwed in . This will tell you what the oil pressure really is . Mine came with enough tubing that I could have the gage on the console inside so I could see what was going on as I drove the car. I am getting about 25psi at idle and around 50 while driving . This is after warm up. Your engine will run better if you just drive in normally as you want to later . It will brake in better. I am not saying to go out and drag race or see what the top speed is . Be mindful of the temp as well as the Oil pressure. Gary

[sideshowbob]

Have you already cleaned the electrical contacts on the sending unit and the wire attached to it?

[Pir0San]

A way to check your oil pressure gauge is to disconnect it from the sender unit, and ground it against the body. Have a friend sit in the car, and if the gauge is working, then when you ground the connector, the needle on the gauge should shoot all the way up, to where it would theoretically have max pressure. If that works, then your oil sender unit is faulty.

[liltuber]

Well I didnt have a chance to work on the car today due to excessive schedule, but I can clear some things up. First, beandip i have the carbs tuned so that it idles high, around 1500 actually. I bought the car right after the engine had been rebuilt. He ran it for about a week but then had to work on his new house that he and his fiance just moved into. He's a cool guy and I can talk to him tomorow. He is a master tech at saturn. Pirosan and sideshow bob i will also try your recomendations tomorow. Thanks everyone for your help and I will keep posted.

shepp

[BillD]

Although I'm pretty sure that the sender is at fault, I had a similar problem where the sender wasn't the problem. It responded well to the replacement of the regular oil pump with an oil pump from a later model, turbo z.

[liltuber]

Ok so I did the grounding check for the guage and the gauge went up but it did it really slow. It in no way shot up. It crept very slowly. Also before my friend got to my house to help me with this I was playing with the connection, wiggling it and what not, and when I started the car it read out good pressure readings, like about 40 at 1500 rpm(idle), but i did take the actual sender out when I was looking stuff over so maybe it had to readjust or something? anyway a little bit later it returned to its lazy self. Im thinking it is the guage, not the sender. Does anyone know how difficult it would be to change that? I only looked briefly, do I have to take apart the dash or does the single guage pop out?

shepp

[sideshowbob]

http://www.atlanticz.ca/zclub/techtips/electricalconnections/index.html

[liltuber]

Well I'm slightly confused now. Recently when I've started the car the pressure goes up to about 40 psi, and it stays there for a while. I can drive it for a while and it stays pretty good, but then after like 15 minutes the pressure gradually goes back down. Is this the sending unit or should I up my oil pump to the one from the turbo car?

[sideshowbob]

Sounds like heat is affecting the reading, switch out the sender. Switching to the turbo oil pump might be a good idea either way, they provide better oiling.