If the blaster outputs water when it's pointed down, it points to the firing valve being open (if all else is sealed). This sometimes happens when the spring that closes the valve weakens with age. This guide
gives more details about this particular problem.
If it's not that, I'd recommend you read SSC's internal leak repair guide
, as it details several strategies to isolate the leak and fix it. As always, pictures or video do help out a lot.
The Drenchenator, also known as Lt. Col. Drench