What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Fuel leak

Bobstern

Member
Patron
I have removed a totally electric fuel system from my RV7A and have redone it to a Vans blueprint system with one mechanical pump and one electric pump. Once complete, everything was pressure tested with no leaks found. Now after 10 flight hours I have found leaks coming from the 90's where they connect to the fuel selector valve. When I was assembling this system, I could not fully tighten the 90's because they would be out of position to line up with the fuel lines coming from the tanks. There must be a simple solution to this I just can't think of it. Any help or ideas will be greatly appreciated.
 
Maybe a stupid question, but did you use a sealant on the threads? Flared fittings don't get any kind of sealer applied, but the pipe thread end needs a sealant on it or they will weep.

Also, if you are trying to clock those and decide you went too far, don't try to back it off even a little, because the threads deform when you tighten it down and it will absolutely be leak prone if you back it off.
 
When I was assembling this system, I could not fully tighten the 90's because they would be out of position to line up with the fuel lines coming from the tanks.

I believe the general spec for NPT fittings is to thread until hand-tight, then go 2-3 full turns more. You should be able to line up the fittings with the tube.

I had a few (like on the brake master cylinders) that needed to go almost one full turn past finger tight, and yeah, it took some wrenching to get it there, and I was worried it was going to crack the boss, but none of them did.
 
HI Bob--- recovered enough to see you at OSH!!!
Mark on the valve where the 90*s need to point, remove them, reseal them, and then reinstall---snug then about 2 full turns + the amount to orient them. IF you go past that point before they are tight, go another turn.
Might be easier to remove the valve from the plane and lock in in a vise----easier than fighting it in the cabin.

Tom
 
Fuel Leak

Tom, great news, I will definitely look you up at OSH. I ordered 2 new 90's thinking I may have ruined them by overtightening them then backing them out to situate their position for the fuel lines. What type of seal are you talking about? I did not put any seal on the fittings at all. BTW, your fuel lines were the BOMB! They made this job so much easier for me, thanks for providing such a great product and caring.
 
Close...

I use Locktite 565, as called for in Section 5 of the more recent plans (Page 5-27).

TDS/MSDS here -- https://www.henkel-adhesives.com/us/en/product/thread-sealants/loctite_565.html

For grins/giggles compare to compare to 567

https://www.henkel-adhesives.com/us/en/product/thread-sealants/loctite_567.html

The 567 seems to be intended for more high temp environments (firewall forward perhaps?)

Locktite 565 holds up better (% strength) in the presence of Gasoline, Acetone, Brake fluid, etc. etc.
 
This website is the greatest! So many people with knowledge that they are willing to share with us who needs more knowledge about airplane stuff. Thanks!
 
Back
Top