This evening I started the pressure test of the fuel tank. I attached the filler neck to the flange on the top of the tank and attached a balloon to the fuel strainer supply fitting. I then began to pump the tank full of air using a bicycle pump. I pumped and pumped the bicycle pump but the balloon would not inflate. I removed the balloon, which was a long type balloon and installed a smaller balloon to the fitting.
I began pumping again and then all of a sudden it was inflated. I put some marks on the balloon with a blue Sharpie so I could monitor if it began to deflate. I went upstairs and a couple of hours later came back down to the shop. The balloon was a little bit smaller, but it was also colder in the shop so I took the tank upstairs into the living room.
In the warmth of the living room the balloon expanded to the original size. I continued to monitor the balloon. It remained inflated at least until we went to bed. In the morning the balloon was quite small. I put the tank back in the shop when I left for work and re-inflated the balloon by pumping more air into the tank. When I got home from work it was small again. I put about 10" of water in the bath tub and began to submerge the sides and ends of the tank into the water. I did not see and air bubbles which would indicate a leak. When I pushed the bottom of the tank under water the pressure on the balloon became too great and it popped. The air rushing out of the tank kept water from entering the fitting.
I removed the tank, dried it off and installed a small orange balloon and started the air test again. The results were the same. The balloon remains inflated for several hours, but eventually goes down in size. I will try a soap solution on all of the joints and fittings to see if I can get the tank to blow any bubbles. I think it is air tight and the air is just escaping through the balloon. We'll see after the soap test.
