Ça va? Ça marche?

Ça va? (as a question, raise your voice at the end) = How's it going? How are you? How's things? Are you ok? Is everything ok? etc.

To make it clear that you are asking a question, you could say, Comment ça va?

Ça va  = I'm fine, it's fine, everything's fine, it's ok etc.

Ça va bien merci = I'm very well, everythings going well (etc.) thank you 
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Ça marche? (as a question, raise your voice at the end) = Is it working?

Ça marche = It's working

Ça marche? 

 Mais non - évidemment, ça ne marche pas!

Ça marche? 

Ah oui - heureusement, ça marche