I purchased a used brison 5.8 the older green case one. I got it on the plane and let it set for 4 years or so, never ran gas thru it at all. Today I tried to fire it up and the carb is not pulling fuel from the tank. This is my first gasser to play with so Im not sure about a few things. Does the tank need to be pressurized? There is a nipple on the side of the motor, what is that for? Any help would be greatly appreciated. I did take carb apart and cleaned it. Its the walbro carb wasn't gummy or dirty or anything inside, all ports are nice and clear.