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Discussion Starter #1
Howdy!

I have a L28 N42 block in a '72 240, and a cylinder balance test
said that one of my cylinders wasn't doing anything. (Hardly
anything anyhow). Then I did a compression check on it, thinking it was probably a head gasket or something, but the compression check was fine! All cylinders between 170-180 pounds.

I just had the ignition checked out with a diagnostic computer and it passed perfectly... (It's crane cams electronic ignition).

If you have good ignition and good compression, what else could
cause once cylinder to not contribute anything?

Thanks a lot for any information, I'm new to this engine stuff. :)

-rr
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Discussion Starter #2
Hello-
I know this sound really remedial but have you checked your spark plug wire to see if you are getting fire to it.

I just take the spark and wire out and start the engine and ground the spark plug and see if their is aspark and if their is it could be your valves need to be adjusted because I had the same problem in my 240 and I adjusted the valves correctly and vala I had 6 cylinders again.

Dustin Morris
 

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Discussion Starter #3
> I know this sound really remedial but have
> you checked your spark plug wire to see if
> you are getting fire to it.

Yeah, it's a good idea but the computer test I did the other day
ruled that out.

> I just take the spark and wire out and start
> the engine and ground the spark plug and see
> if their is aspark and if their is it could
> be your valves need to be adjusted because I
> had the same problem in my 240 and I
> adjusted the valves correctly and vala I had
> 6 cylinders again.

Maybe that's what I'll try then. The valves *do* really need
adjusting on that thing, (I don't think they've been looked at
in around 16,000 miles). And one of them was making a little
noise anyhow.

Thanks very much for the help sir!
-rr
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Discussion Starter #5
> check the injectors
> run some techron thru it an see if that
> don't change anything.

Well, the engine is in a '72 240Z and has been converted
to '72 SU carbs... so there aren't any injectors to check.

I like the valve adjustment idea... so I think I'll try that
first.

Thanks for the idea!
-rr
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I am not fimilar with that testing thing you used, but what you really need to make sure of is that the plug is firing, not just that end of the wire is getting power. The reason is that it may be good out of the car, but it can not fire under pressure. This happened to my dirt bike a couple times and it took hours of work and frustration to figure out it was the spark plug. It fired great out of the cylinder under no pressure, but not in the cylinder. I replaced it and it started right up and ran perfect. Just double check, for $.89 you can try it and it may do the trick. If the valvues are out a little, it would still help out but miss a little, you would be able to hear it out the tail pipe. Unplug the wire while it is running, and if it makes little difference in how the thing runs, there is your problem. Be careful though, you can shock yourself pretty good if you are not.
Good Luck,
Joshua L.

Adjust those valves anyways if they need it.
 
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