I didn't siphon the gas, so I'm thinking it might be bad gas, but I have a '99 C3500 pickup that sat for 7 months. I put a brand new battery and sprayed a little Carb Cleaner, and after it choked (revved up and down), it eventually idled perfectly. I let it run for about 30 minutes just to clean out the carb. A week later, I tried to start it and it simply clicked (all gauges and dash lights come on). So, I connected it to a running car battery, and it would crank over. Tried more carb cleaner and it would rev up but then stop after a few seconds. After about 15 minutes of this, now it's back to simply clicking. Does anyone have suggestions I should try next? Thank you!