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1983 280zx turbo engine

Dave WM

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1 hour ago, Patcon said:

So what changed?

I wish I knew, only thing I did was add the uv dye to the system. Clearly I will be retesting, I am using the fluid from the same bottle, I should have sniffed from the tail pipe to confirm color change, will do that next time. I will conduct more test over the coming days. Thing is IIRC I had the same thing happen on the N42/MN47 spare engine, failed at 1st then tested fine later and ever since. REALLY bugs me but if I can't get it to fail again (and remember it never overheated when it did indicate fail) then I will take the W, don't want to look a gift horse in the mouth. 

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ah, a variable...

whilie I was putting the engine away for the day I recalled my plan to look in the cylinders (before doing the last chem test that was a win.

My plan had been to inspect for dye in there, in prep for that I had only installed the plugs finger tight to briefly run the engine to circulate the dye.

SO, is it possible that some of the exhaust pressure was leaking past a less the fully tighten plug, thereby reducing the combustion chamber pressure enough to allow for the test to pass? Its at least something to go on. Its too late for me to run the engine now, but will make sure the plugs are torqued to spec an will try again tomorrow. Geez I hope is passes, but if not at least the puzzle will be solved.

And if it does fail I think I will try running while disabling one cylinder at a time (pull the fuel injector connector off). That should allow me to narrow down the issue. I actually started down the path earlier before running it in the video. I had removed #6 plug, thinking it would lessen the load on the engine to not have to compress just the air, well silly me, engine ran like crap, massive air leak I guess, so I reinstalled the plug (hand tight) and the video was made. 

Now to be clear the plugs were not loose, fully seated, and I could not detect any odd noises while running making the video, Just snugged up with to the washer.


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12 hours ago, Captain Obvious said:

Man, I hate unexplained things... I sure hope you figure out what's going on with those readings.

Do you know what it is that the Swedish enlarger pump is looking for? What chemical(s) is it supposed to detect?

I dont know for sure, but I think it will detect C02 from and I presume C0 as well. 

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Ok tested again today, this time with the plugs torque to spec, again passed with flying blue colors. Only thing I can think of is something in the coolant that had to boil off. Perhaps all that WD40 I used (filled it with the stuff then drained it out to prevent rust after rinsing the evaporust out. Maybe there was trace amounts still in there? I guess as a test I could simply dump some WD 40 back in and see if the test for gas comes back positive again. Or I could move on to the turbo install. With the 02 sensor I am able to monitor the Air/fuel ratio pretty well. I could just keep an eye on that and try it with boost on the NA setup. 

I did test the color change by sampling the exhaust from the muffler, turned yellow right away.

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  • 5 months later...
  • 7 months later...

got it all disconnected and back on the test stand with the test stand key switch so I can drive my car, and will be testing that IAC when it comes in. Before disconnecting everything I tried multiple times on starting, no glitch like in the video, cranked right up. 

I looked at the exhaust, looks like the bend is about 1" lower (so the down pipe 1st bend back would put the exhaust tube about 1" lower than the stock position. I could probably just live with that, but I dont like idea of the exhaust hanging any lower than it already does. So I may try cutting and welding it back to get to a more stock position that I can then work with back to the muffler. OR I may just use the MSA exhaust designed for this. The only issue I have with that is it does not have the EGR bung and not sure if I could add one. Thats all down stream some as I dont plan to do the swap until prob next year. I want to enjoy it as is for a while. 

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