Tank venting

[Dgamble]

I noticed yesterday as I was removing the fuel cap from my right side tank, there seemed to be a vacuum in the tank. This was exhibited by a reluctant-to-be-removed cap and the sound of air moving into the tank once I got the cap off.

Does this possibly indicate a blocked fuel vent? Is there a way to test it?

[Mike S]

Yes, I would suspect a blocked vent for sure.

I am able to slip a section of 1/4" hose over my vents, and blow in to check for blockage.

Do this with the fuel cap off-----otherwise the tank will act like a balloon, and will blow back at you when you stop. Plus with the cap off, you can hear if it is free.

[jfogarty]

I blow in to the vent lines on the Cardinal during my preflight and that works great. I will be using that same preflight process for my RV9A.
The Cardinal never blows back, I'm not sure of the difference? I hear the air entering the tank and then I know the line is open. There is a great article on this in Sports Aviation this month, The Most Unforgivable Sin, page 25. Do most RV pilots check the vent lines before each flight? Thanks.

Jim

[Walt]

If you don't have screens on your vents (or religiously use covers) you are asking for problems. I've personally cleaned out a number of pitot tubes totally blocked by mud daubers.

Link to AOPA article

[jdeas]

Originally Posted by jfogarty

I blow in to the vent lines on the Cardinal during my preflight and that works great. I will be using that same preflight process for my RV9A.
The Cardinal never blows back, I'm not sure of the difference? I hear the air entering the tank and then I know the line is open. There is a great article on this in Sports Aviation this month, The Most Unforgivable Sin, page 25. Do most RV pilots check the vent lines before each flight? Thanks.

Jim

There is a vent on both tanks on the 177 and if the fuel selector is on both I can see this happening. On a low wing aircraft I bet you have to keep the cap off.

JD

[6 Gun]

We use pipe cleaners to stick in vents when sitting in hangar cheap and easy to carry spares and if you left one in it would blow out and if it dont it will still let air pass.
Bob