fuel tank vent patency

does anyone have a sure fire way to test the patency of my fuel vents?

i was thinking about setting fuel selector valve on OFF, taping a vacuum to the fuel filler port, turning on the vacuum and feeling the vent port at the bottom of the firewall for suction.

seems simple enough I guess but it's such a critical element i can't help reaching out for opinion in case i'm missing something.

comments invited

thanks in advance

jeff H
n377cp, KWVI

Keep it simple. Fuel valve off, tank cap on, just blow into the vent (do not use a compressor - your lungs are about right). Use vinyl tubing if the vent is too icky. You should feel the pressure building. Remove your mouth, air should flow out.
Repeat with tank cap open. Should be little back pressure, no air flowing back out.

What Bob said.

I use a hose about 6' long, attach to the vent, remove the cap, blow, and listen for air motion at the filler hole.

DO NOT get a vacuum any where close to the fuel tanks if they've ever had fuel in them.

A friend of mine tried to clean up spilled gasoline with a shop vac. He accidently invented a jet engine complete with afterburner.

Bevan

Thanks

Thank you gentlemen for your thoughtful responses. Yes, a simpler approach is agreeably better and the method was nicely articulated thank you again. But before pragmatism comes survival so I am especially thankful to my countryman for his aid in helping me avoid the rocket simulator exercise.

Regards

Jeffrey Hodgson
N377CP, KWVI