Startup problem with Getz

Hi to everyone. I've got a startup problem with my Getz!! Sometimes I have to start the engine different times before it works well (maybe 4-5 as 15, for example as this morning)
It's not an electrical problem, I'm sure I hear the pump, it seems to switch on, but it fails! I heard it can be the butterfly valve, but I'd like opinions or a confirmation During the summer the problem seemed to be absent, but now it's becoming "fastidious", and I'm a bit scared for the battery. Thanks to anyone who will help me!
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