Dead Cylinder #3

garmartin

New User
Dead cylinder #3! I have been around Ford N tractors my whole life and in the last 7 years during my retirement, I have started buying nonrunning N tractors to fix up and sell just as a hobby. I have come across a 9N that is driving me crazy. The initial problem was a stuck open exhaust valve on #3. Was able to use Pblaster and transmission fluid to free it up and is working fine except, the cylinder is still dead. Originally there was 0 compression but after unsticking the valve, it now has 95psi. The other cylinders vary between 95 and 105psi. Checked for spark and it seemed week so I replaced the distributor and points. Cylinder #3 still dead. When I pull off the spark plug wire on #3 while running there is no difference. The new 437 sparkplug in cylinder #3 still looks brand new and does not get hot to the touch while the tractor is running. Thinking there was a manifold problem, I removed the manifold and inspected for a problem but found nothing wrong. While the manifold was off I inspected the valves but found nothing wrong. I took a piece of paper and held up to intake on block and turned engine over to see if there was suction to manifold and carburetor and there was. Put manifold back on with new gasket but cylinder #3 still dead! What am I missing?
 
(quoted from post at 19:57:47 08/06/21) Dead cylinder #3! I have been around Ford N tractors my whole life and in the last 7 years during my retirement, I have started buying nonrunning N tractors to fix up and sell just as a hobby. I have come across a 9N that is driving me crazy. The initial problem was a stuck open exhaust valve on #3. Was able to use Pblaster and transmission fluid to free it up and is working fine except, the cylinder is still dead. Originally there was 0 compression but after unsticking the valve, it now has 95psi. The other cylinders vary between 95 and 105psi. Checked for spark and it seemed week so I replaced the distributor and points. Cylinder #3 still dead. When I pull off the spark plug wire on #3 while running there is no difference. The new 437 sparkplug in cylinder #3 still looks brand new and does not get hot to the touch while the tractor is running. Thinking there was a manifold problem, I removed the manifold and inspected for a problem but found nothing wrong. While the manifold was off I inspected the valves but found nothing wrong. I took a piece of paper and held up to intake on block and turned engine over to see if there was suction to manifold and carburetor and there was. Put manifold back on with new gasket but cylinder #3 still dead! What am I missing?

This may sound like a simple question but, are you getting spark to #3 cylinder now? You replaced parts but you did not address this question.
 
gmartin, did you do as Shaun Wallace suggested in your original post? If that exhaust valve is slow to close, you could get a good compression reading at starter cranking rpm, but perhaps not at running rpm.
 

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