What Comes Out of These Tubes?

[HopePilot]

The other day, after priming fuel pressure with the fuel pump, prior to startup, I noticed something dripping from possibly the larger of these tubes.  It made a very small puddle, which appeared to be fuel, but I thought this was where oil escapes, but I've only got 7 qts. in there right now.  Will fuel drip from this area if you over prime?

 

[KSMooniac]

Are you talking about the tubes that exit the back of the cowl on the pilot's side?  If yes, there is one tube from the breather outlet of the engine (oil can blow out here) and another from the bottom of the induction pan...which will drip fuel if you over-prime or flood the engine.

BTW, many Lycomings will blow oil out if you fill to the 8 qt capacity.  Many will blow it out if you put in more than 6, too.  I generally fill to 6 qts for that reason.  YMMV

[HopePilot]

Yup that's what I was talking about.  Thanks.

[jetdriven]

IIRC its called th "sniffle valve".  It is supposed to close when engineis running or else it pops and backfires at idle.   http://www.donmaxwell.com/publications/MAPA_TEXT/External_Hoses/External_Hoses_Tubes.htm

[Piloto]

The dripping that you are seeing is perfectly normal after you prime the engine before start. It comes from the excess fuel injected into the cylinders that drains down via the intake pipes into the crankcase intake plenum at the bottom of the engine. At the bottom of the plenun/case there is small AN fiting with a hose that discharge this fuel by the left cowl flap opening. If the excess fuel is not drained backfiring can occur during engine start.

José