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Discussion Starter #1
Okay, I am still on the path to getting my sitting-for-10+-years 240z running.

Since my last post I have restored the fuel tank, installed the 280zx distributor, replaced the primary and secondary fuel pumps, installed the Zthereapy SUs and got my car to actually start!!!!!

Now my current problem is that I can get the car to start on starting-fluid, but it instantly goes to redline and stays there.
I cant figure out why.
  • I have set the SUs for a "base tune" and it runs this way.
  • If I back off the butterfly adjustment knob fully, it still goes to redline.
  • If I screw the needle adjustment all the way closed I can kill the car, but nothing in between seems to affect it.
  • Yes the butterfly are "closed" when the car is off
  • Yes, the return springs are installed
I was told to check for a vacuum leak, but that doesn't really make sense to me given that the crank-case vent is basically a vacuum leak all by itself. I tried blocking that off as a test without any change.

Any suggestions?
 

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Wait on a poster with more expertise and I don't remember the details of the carb linkage but it sounds like the butterflies are being pulled open by engine vacuum draw. Is there a set screw loose on the throttle shaft linkage?
 

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Is there oil in the piston dampers?
 

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Discussion Starter #5
Wait on a poster with more expertise and I don't remember the details of the carb linkage but it sounds like the butterflies are being pulled open by engine vacuum draw. Is there a set screw loose on the throttle shaft linkage?
Perhaps? I don't know of any set screw that effects how the butterfly is pulled open though. If there is, I would love to know as that could certainly affect it.
 

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just a side note...the crankcase vent has nothing to do with vacuum in your intake. It only vents the positive pressure in the case from piston blowby.
 

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Check for a vacuum leak. Get a pack of cigarettes and a hand pump from harbor freight and plug one end of the pump into the carb and start pumping/look fro smoke sneaking out. You probably have a vacuum leak.
 

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Mr.Pan:

Let's see if we have this right...

The air cleaners are off and you're looking in the throats at the pistons with the engine off. You lift each piston, noting the relative resistance between them, and then drop both that hit bottom (with an audible thunk) at the same time.

Then you lift each, and with a flashlight, note the position of the butterflys; each are closed.

Someone now starts the car (keeping away from the accelerator), and you watch the pistons snap all the way up (again with no throttle, butterflys still closed) as the engine redlines.

Is that about the size of it?
 
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