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Fuel drain in a high pressure system

stringfellow

Active Member
Perhaps I'm losing my mind but I posted this last night and I don't see the thread anywhere. In the event it was moderated out of existence, perhaps the mods could PM the affected so we're not left scratching our heads.

I'm installing an EFII system. The low point in my fuel system is not the wing tanks, it is the belly. I would like to add a sump drain on each supply line just before the fuel selector valve, but it was suggested by someone that in a high pressure system, it is conceivable that the spring-loaded Curtis valve could be partially opened by the high pressure flow in the line, introducing air.

I have a hard time believing this could be the case with the low cross-sectional area of a drain plunger. Can anyone shed any light on it? If it is an issue, were to find lock-closed sump drains?
 
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Unless you are routing the fuel lines outside of the belly there is simply no way for the fuel lines to be lower than the designated sump location in your fuel tank.
Even if the belly of your RV-10, unlike any other 10 was in fact lower than the fuel tanks, it would make no sense to route the fuel lines all the way at the bottom of the belly. When you get to the fuel selector you'll have to bring the lines up to the level of the selector in- and outlets. Even if you were to use an extension on the fuel selector handle, you'd still be off the belly skin by several inches and thus several inches higher than the tank drains.
Can't say if those drain plungers are adversely affected by high fuel pressure but I am quite sure that adding unnecessary fittings will not improve your fuel system over a conventional high pressure system.
 
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