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Discussion Starter · #1 ·
cylinders 1, 2, and 3 are not producing power. I can take of the wires, and no change.

Ok, The valves are adjusted properly to the best of my ability on the head.

Fire is getting to the plug.

The plug fires when I remove it from the hole, and attach it to a plug wire.


I switched the float bodies that you take off with four screws from the back SU to the front SU, and no change.


Gas is getting through the line, I can crank the car, and it comes from the rail, and If I disconnect the line that goes from the fuel bowl to the SU, it drains the fuel bowl lickety split.

The Throttle butterfly is working properly on the SU.

The Needle/Piston is moving freely.

what else COULD there be?

-andrew
73 240z
82 zx
 

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Your engine should run if you've got the three basics: gas, fire, and compression. Testing spark plugs in low atmospheric pressure conditions doesn't necessarily mean that they are working in the high compression environment of an engine. If you don't have access to a high pressure spark plug tester, then in the very least the spark you see at the plug should be zapping hot and blue. Yellow sparks are weak and indicate bad ignition components.
If I read your post right, when you disconnect your front carb from the fuel line and start the engine, the fuel in the float bowl is consumed. That you have fuel there at all indicates that you don't likely have a gas problem.
Compression is the last, and ugliest consideration. After confirming that the spark you're getting is hot, drag out a compression tester and see what's going on. This doesn't seem likely to be the problem, because the problem is consistent through all of the first three cylinders. If you've got consistent compression, then let us know those sparks look like. You also might try hosing out the internal ports, etc. on the front carb with some carb cleaner.

Good luck.
Q
 

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Discussion Starter · #3 ·
I blew out the Su hole with compressed air, and a few bits of black stuff came out, but nothing much to speak of. I do not see any fuel spraying up out of the needle hole when the car is running, and I do not feel any either when I push up the piston and hold my finger there. I also have ZERO PSI on cylinder one. I couldn't have broken a ring driving it home like this, could I? It's only been drove about 5 miles w/ 3 pistons running
 

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BINGO!

Zero PSI is a very bad thing. Even if you broke two rings, the third should still provide some amount of pressure, no matter how small. If you have -0- pressure then either you made a mistake when you took the reading or, using technical jargon, you are screwed. I'm thinking broken valve head (which would have been very noisy) or holed piston, or holed piston from broken valve head bouncing around in the combustion chamber. Welcome to the wonderful world of mid-winter engine rebuilds.
Pull your valve cover and see if everything looks normal on #1. You might try spraying some WD-40 into the #1 hole and test the compression again. If it comes up, then you likely have a ring problem of some kind. If it remains at 0, then your engine has flat-lined and needs to be taken apart.
In answer to your question, engines can fail at any time. The amount of time driven really doesn't matter. More important is HOW you drove prior to the break.
Good luck and keep us posted.
Q
 

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I dunno

I wonder if he didnt use the compression gage right. Why would a bad cyl cause 3 to not run at all? Its obviously a problem with the carburator.

Yes he might have a bad cylinder, but that is another problem.
 

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Re: I dunno

At this point I would make sure the valves are closed on # 1 (lobes pointing up) and pump compressed air into the cylinder through a fitting screwed into the spark plug hole.

You will definitely hear the air escaping through the tail pipe (bad exhaust valve), intake manifold (bad intake valve), coming back up from the oil pan to the valve area (bad piston).

Wayne Monteath
Masham, Quebec.
 

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Re: I dunno

If the intake valve is blown to peices on #1 then maybe the air is blowing back into the intake manifold strong enough to kill the suction pulling air in to 2 & 3.
 
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