If you're wondering if your anti siphon valve is stuck, or clogged, here's a test....

[Lou C]

I had mine replaced years ago, always wondered if there was a way to test it to make sure it's not starting to stick again. I have a pressure and vacuum tester for the outdrive, so I rigged up a way to put a vacuum on a new un-installed anti siphon valve and see at what point it opens, about -2" of mercury. So if it holds much more vacuum than that, a good sign it might be contributing to a fuel delivery problem you could be having. This could be useful if the old one has been installed a long time and might not come out easily....