joshuadreed Posted March 21, 2009 Share Posted March 21, 2009 78 280z 4spd man. While driving I noticed I had very high oil pressure, it was nearly constant at 80psi. Once I arrived at my destination I checked my oil level and it read at the minimum level. Ignoring the Oil pressure I just put more oil in and drove it home. The car runs fine but I'm actually loosing oil and the pressure is still way to high. It idles at about 60-70psi and as soon as I bring the rpms up it shoots to 90 and stays. I'm sorry if this goes on and on but I want to make sure and give you all of the details. As far as oil consumption is concerned I did an oil change about a month ago and had it filled to the max level. It took me about 2 quarts to get it back to the max level. I'm using Royal Purple 5w-30 oil. Another little detail is that it seems to be spitting black stuff out of the tail pipe at high rpms(oil?). I noticed this when I was sitting in my garage and around 4500 rpms it begins doing this. So my first thought was that I needed a new oil pressure sender but now I'm not so sure; is there any way to test my sender without buying a new one? Does anyone have any ideas what the problem may be? Thanks- Joshua Quote Link to comment Share on other sites More sharing options...
woldson Posted March 21, 2009 Share Posted March 21, 2009 Mine (83zx na) will be at eighty when cold. Idel will be up close to yours as well. When heated up, not nearly so high. (really warmed up) Could just be a gauge problem, the loss of oil should not be a factor in why it is soo high. Search, there was some advice to a mach. gauge on the engine at the sensor location, if I remeber correctly. Quote Link to comment Share on other sites More sharing options...
joshuadreed Posted March 21, 2009 Author Share Posted March 21, 2009 So what I'm guessing is that I can use any $10 dollar liquid pressure gauge with a btp to npt adapter to check my sender. Does this sound right? Quote Link to comment Share on other sites More sharing options...
Careless Posted March 21, 2009 Share Posted March 21, 2009 So what I'm guessing is that I can use any $10 dollar liquid pressure gauge with a btp to npt adapter to check my sender. Does this sound right? you could! Quote Link to comment Share on other sites More sharing options...
joshuadreed Posted March 22, 2009 Author Share Posted March 22, 2009 So... I changed my pressure sender and the pressure is still high, it's as if once the pressure increases it just stays there. So I decided to drain my oil and replace the filter in case it was broken and or plugged. It wasn't the filter. When I did this I found a new part of the problem. My oil is now water thin, smells of gas and is brown(which is wierd considering it was purple). So, what is causing my oil to fill with gas? I've done some searching but can't find much. : ( Once again Thanks for all your help. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted March 23, 2009 Share Posted March 23, 2009 How many miles did you have on that oil before you changed it? Quote Link to comment Share on other sites More sharing options...
joshuadreed Posted March 23, 2009 Author Share Posted March 23, 2009 About 1200 miles. I did an oil and filter change less around a month ago. I've only had the car for about two months and I'm actually very new to mechanics. I like to think I'm doing pretty good so far. Quote Link to comment Share on other sites More sharing options...
joshuadreed Posted March 23, 2009 Author Share Posted March 23, 2009 Some history of the car that may be helpful... I bought the car from the 2nd owner who said he was not sure whether it was at 40,000 or 140,000 miles because he was selling it for his dad. People who have seen it in person say it's probably 40,000 because it's in good condition and things like the seats are nearly perfect. Since I bought it I have switched to a 240sx throttle body, mainly so I could use a throttle cable. I replaced the radiator because it had been seeping for who knows how long. My heater core or valve is leaking so its just not hooked up right now. I had a pretty bad exhaust leak so I've replaced the intake/exhaust gaskets. While I was in there I put new electrical connections on almost the entire efi harness, put new seals on the injectors and new fuel hoses, vacuum hoses and hose clamps thru out. I'm sure there is more but that is all I can think of right now. Hope that helps Quote Link to comment Share on other sites More sharing options...
joshuadreed Posted March 23, 2009 Author Share Posted March 23, 2009 I just found some info searching Zcar.com and it looks like it may be my valve seals so I'm going to go check my compression and then I'll let you all know the results. Also I just got off the phone with my dad who was a mechanic for many years but he's not familiar with imports; he says it may be the fuel pump leaking at the diaphram if it's mechanical. So another question I have is whether or not the fuel pump is electric or not on my 78. I will research for this as well as more info on the fuel system but if I could get a quick answer it would be very helpful. Quote Link to comment Share on other sites More sharing options...
joshuadreed Posted March 23, 2009 Author Share Posted March 23, 2009 Looks like I have an electric fuel pump so I will be doing a compression test soon. Quote Link to comment Share on other sites More sharing options...
joshuadreed Posted March 23, 2009 Author Share Posted March 23, 2009 Haven't tested compression yet but after talking to my dad again we've come up with a new theory... It's a little long winded so bear with me. The oil pressure sender has two pins on it, one for the oil pressure gauge and one for fuel cut in the case of a wreck and fire. Since I have high oil pressure(still don't know the cause) the fuel pump doesn't shut off when the engine does. If the ignition is on and the sender still sees engine oil pressure it will keep pumping gas thru the system. This still isn't a problem. The next "if" in this theory is that I may have one or more leaky injectors. So basically whenever I leave my ignition on to test something or just to see what the gauges are reading with the engine off I may be pumping gas into one or more of my cylinders. I have experienced a lot of smoke on start up before so maybe this is it or at least the reason for gas in my oil. I'm going to test this tommorow by leaving the ignition on for a while and seeing if that causes a ton of smoke on start up. Quote Link to comment Share on other sites More sharing options...
gwnwar Posted March 23, 2009 Share Posted March 23, 2009 Have you put a fuel pressure gage on the fuel line. does it hold.. pressure or drop off fast like leaking.... Quote Link to comment Share on other sites More sharing options...
joshuadreed Posted March 23, 2009 Author Share Posted March 23, 2009 That's definitely going to be my next test, thanks for the advice. It seems so obvious to test that but for some reason the gears in my brain have started to just mash into each other lately. Quote Link to comment Share on other sites More sharing options...
skib Posted March 23, 2009 Share Posted March 23, 2009 Hope you get this figured out in time for next months meeting man, let me know if you need any parts, I might have em. Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted March 23, 2009 Share Posted March 23, 2009 first check the sensor connections its not un-heard of to have a bad connection, shorted or open connections, the fuel pump should not run if the ignitions not in the on- possition, verify with a vom meter that the pumps not getting power when the keys removed. next find the source of the fuel leak, yes as you surmised itmight be a leaky injector but that may not be the only problem. remove the new ,old oil, and replace it carefully checking for new fuel contamination after, a few days, running fuel oil mix will quickly destroy rings Quote Link to comment Share on other sites More sharing options...
Careless Posted March 24, 2009 Share Posted March 24, 2009 is think your oil pressure is being hightened by the crankcase pressure that your cylinders may be blowing by. have you checked to make sure all vac lines and all PCV hoses are not plugged and the oil is circulating out of the crank case? Quote Link to comment Share on other sites More sharing options...
joshuadreed Posted March 24, 2009 Author Share Posted March 24, 2009 Ok guys... Sorry for the double post and I would have given an update sooner but I was having some problems with hybridz. Last night I finally got fresh oil in it, which I would have done sooner but I couldn't get to the store and didn't want to put the bad oil back in. With the fresh oil the pressure sender is working perfectly. I think without oil to lubricate it the sender was not returning properly and showing I had much higher oil pressure than I did. My dad thinks I may have been using to thin of an oil and it was just washing past the rings. He's told me to watch my oil consumption closer and start fresh and I'm doing just that. I am still going to do a fuel pressure and compression test some time in the near future. Thanks everyone for your continued help and I will let you all know how this batch of oil turns out. Quote Link to comment Share on other sites More sharing options...
joshuadreed Posted March 24, 2009 Author Share Posted March 24, 2009 Also I wanted to add that nearly every vacuum hose is brand new and I just put a new pvc valve in too. I will however double check all these hoses. Quote Link to comment Share on other sites More sharing options...
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