Every time I turn on the sprayer at the sink, all pressure goes out of the main faucet, but nothing really comes out of the sprayer, either--just a few drips. When I let go of the sprayer handle, the water in the main faucet does not come back on. Only after leaving the faucet handle up for several minutes or moving it on and off many times does it come back on. I'd like to fix it myself and not have to call a plumber. Any ideas what's going wrong here? Thanks!