I found a little fuel in my overboard vent line of my Tempest fuel pump
(Lycoming IO360). I used the yellow Tygon fuel tubing for the vent line
which is transparent. I have never noticed any fuel in this line before. I
have never disassembled one of these pumps, so I am not sure what could
cause this other than a bad diaphragm or maybe a bad seal. Does anyone know
of another reason for fuel to be in this vent line?

The volume was small-- about 1 1/2 inches of fuel in the 1/4-in. line.
Cleaning it out and starting the engine did not produce more in the line.

My pump has operated for 1040 Hobbs hours. Maybe it's time for a new pump,
although I have been told that they usually last to TBO.

Mike Reinath
LNC2 N3602M @ 1040 hrs
San Jose, CA