Anything you do in your startup is going to be a risk. Admittedly, this is one too. You have a genuine concern here, that if you try to crowd fund and the effort fails, that it will scare off investors. Some people will definitely see a crowd funding failure as evidence that the idea isn't going to work, at least not in it's current form. Indeed, if you don't get what you were expecting to get, you should be asking yourself the same question.
But in the very early stages of a startup, you need to be moving as quickly as you can towards validating your product. Proving that it has a market and can get traction. Crowd funding is one possible way of validating (or invalidating) your idea.
(Also, please note that having a successful crowd funding campaign, or even getting angel investors does not prove or disprove the value of an idea, it just provides some evidence towards that end.)
So while it's a valid concern to have, at some point, you've just got to get your idea or product out there and test it in some form or another. If it works, then mission accomplished. If it doesn't, the sooner you can determine that you need to modify your idea or find a whole new idea, the better.
Don't be so afraid of rejection that you fail to ever get your product out there in front of potential customers.