Bryant plus 90 - code 34 and after code 14

I have an old gas furnace Bryant Plus 90. i read a lot on the forum about this issue (the gas don't ignite). It's looking like the gas it not leave to the burners even if the valve it's "working" - (clicking noise from the valve on start). All the steps are OK till the gas it's suppose to lite. All it's working till then. I strongly believe that the valve it's not working mechanically. Somehow the gas it's not going to the burners.
I don't know how to find the problem, the reason of that issue.
If somebody have some ideas please let me know. I need to talk about this to solve the problem.

 

Hoe can I verify the gas valve if it's working properly? I think that sometimes this valve it is stack or somehow it not release the gas to the burners.