2 gall plastic barrel 2" cap with vent, you know the sort. never pressured up, and its a new barrel new cap,no leaks. I decided on fresh yeast from off my spin plate, looked fine enough, added another ounce of sugar, and a week later still no pressure. Further test today and i got a fierce reaction when i put half an ounce of sugar in.No bad smells,- What is happening here? Starsan was used throughout my sterilizing procedures.
When you pour sugar into a CO2 solution it will bubble up as the sugar particles force some CO2 out of solution. A sugar addition should cause it to pressurize fast if there is a lot of yeast and no leaks in your system. One problem may be that yeast need oxygen to grow their population fast and not much is usually available at the end of a brew. Why did you need to add fresh yeast and how much did you add?