Spark at plugs, but cyl not running

[Troyb56]

Ok, here we go again. 1971 60hp johnson. I had cyl 1&2 running and 3 not. Took off carb and got fuel to number 3 now. You could pull off plug wires off 1&2 and engine would bog and 3 nothing. Now only cyl 3 is running and 1&2 you can pull plug boots off and motor does nothing. There is spark coming to all plug boots when i check each plug wire. Any help is really appreciated. Thanks

 

[Monte1961]

Re: Spark at plugs, but cyl not running

Are the plug-wires right?

 

[Borgey401]

Re: Spark at plugs, but cyl not running

Have you tested how strong spark is on each cylinder? Also, have you tested compression on each cylinder?

 

[Troyb56]

Re: Spark at plugs, but cyl not running

Yes all plug wires are right and compression is great on each cyl around 135. I just bought the tester to check spark length, but all are fireing when checked with plug outside cyl.

 

[Monte1961]

Re: Spark at plugs, but cyl not running

Is it a possibility that key-way is sheared? Just a thought.

 

[Troyb56]

Re: Spark at plugs, but cyl not running

Idk, but I had one mechanic set the points and rebuild all 3 carbs, but said he couldn't pinpoint why the one cyl wasn't fireing but getting spark, since then the one that wasn't fireing is and the other 2 not. At first I thought that I just had a fuel problem on the one that wasn't fireing because plug came out dry and clean, since then that plug is wet and is the only cyl that is running.