Chasing fuel line leak.

[docjjrmd]

Well I am glad I listened to my big toe itch. For background I am building an RV-12iS and working on finishing up the fuselage. I decided to high pressure test the fuel lines before riveting the avionics bay floor. Pumped the lines (not the tank!) up to 40 psi. Oops, leaking. First leak found was on the bypass block and was fixed with another 1/2 flat turn on the nut. That took care of the majority of the leak but was still losing pressure very slowly. Stood on my head and used mirror to look at bulkhead fittings with leak detector. These are not the easiest to get to at the best of times. Right hand connector had small ring of bubbles. Studied it for a while realized only way to get to it was to drop the rudder pedals. That opened everything up vision and access wise. Cranked on the nut another 1/4 turn. Leak slower but small ring of bubbles persisted. At this point, only option I could see was to pull the connection apart, see what was happening. So as can be seen in photo below, found a small nick or crack on edge of flare at 3 o'clock and some dicey looking area at 6 o'clock. I presume that is cause of leak. Pulled the fitting off the firewall, looks ok. The plan going forward is to cut flare off, re-flare, and retest before going further. I will also replace bulkhead fitting with new simply because I have one at hand .

I certainly feel for those builders that have to track and repair this connection after avionics and controls are installed. Instructions cover leak testing of fuel tank but silent on fuel line system until fuel pumps installed with power plant kit. I'd suggest the addition of a high pressure test after fuel lines are fabricated and installed so access is easier and familiar. - JJR