There are many ways to leak check the tank. We have had good success with several, but we have gravitated toward putting 1 PSI (not more than 2 PSI) of air in tank and checking with soapy water for bubbles. You can make a test setup to measure the 1 PSI accurate and cheaply. It is a basic manometer.
1. Install the fuel cap
2. Us a AN-6 fitting cap or install the quick disconnect fitting to the fuel pick to cap it off
3. Insert an air fill valve (called a Schrader valve) into the drain flange. You will need either a 1/8 or ¼ NPT fitting. Verify your actual flanges to see what size you have. We get them from Mc Master Carr (Part #8063K41 for 1/8 NPT and 8063K37 for ¼ NPT). Install with teflon paste, use caution not to over tighten.
4. Flare a 4 inch long scrap of ¼” 3003 tube and attach to vent fitting with nut and sleeve
5. Attach approx. 8 ft of cheap ¼” clear tube to the aluminum and secure with a hose clamp.
6. Make an approx. 3 foot loop in tubing and secure to scrap board per photo with zip ties.
7. Fill the “u” in tube with about 18 inches of water and mark where the water is.
8. Measure up from the “water level mark” 14 inches
9. Add air slowly watching the water level as it rises up toward the 14 inch mark. An old hand tire pump works well but a compressor is fine also, just go slow. When at the 14 inch mark you have 1 psi inside the tank. It will visibly “bulge” a little.
10. It should hold at the 14 inch mark. Use a mixture of dish soap and clean water and apply along all seams and rivets with a soft brush or use a spray bottle.
Even a tiny leak will show up as either a stream of tiny bubbles, or it will blow a huge bubble. Work slowly. We take about 30 minutes per tank. The ends of the tank at the rib and tank backs are most common leak points we’ve found when repairing brand X fuel tanks.
OK great! It passed! You now get to go eat some chocolate cake, enjoy a beverage or celebrate as you would any victory!
