How snug should fuel cap be?

I'm a brand new RV-12 owner. Hence, my very basic question: How snug should the fuel tank cap be when it's on and secured in place?

I ask, because the first time I put fuel in my plane, the cap was so tight I had to use a tool to lift the metal flap, and I could barely get the cap out of the tank neck. In fact, I thought the cap may have threads that screwed it into the tank neck, so I twisted the cap using its metal flap. That was not a good idea, because by doing that, I got the disks out of alignment, and then couldn't get the cap into the neck or put the flap down.

So I disassembled the cap and reassembled it, and now the flap is nice a loose and the cap fits into the tank neck easily. The cap also comes out of the tank neck easily -- perhaps too easily. I'm concerned it may bounce out while I'm taxiing or flying.

That's why I ask how snug should the cap be, when it's in the tank neck and the metal flap is in the down position?

My "breather hole-style" cap has been adjusted to be a slightly snug push fit on initial installation. After the lever is depressed the cap is very securely retained in the fuel port -- there should be no looseness between the cap and port when the lever is fully depressed. I use my car key to initially lift the lever and then the cap can be easily wiggled out. By the way, if your fuel cap is of the original "breather hole-style" like mine it is a good idea to test blow through the breather hole during each refueling or on preflight to ensure that the hole is open and clear.

Fuel cap instructions

[email protected] said:

I'm a brand new RV-12 owner. Hence, my very basic question: How snug should the fuel tank cap be when it's on and secured in place?

I ask, because the first time I put fuel in my plane, the cap was so tight I had to use a tool to lift the metal flap, and I could barely get the cap out of the tank neck. ?

Click to expand...

After lifting the flap to vertical, push the flap vertically down. It will only move a small amount, but the cap should now be easier to remove.

Additionally, even a properly adjusted cap can be a bit tight on the center seal.
If after lifting the latching lever you push in on the lever towards the cap it usually removes from the opening easily.

Thanks to all of you who responded to my question. I followed your advice, and the fuel cap fits perfectly now.

I was a renter for years until I bought my RV-12, so I never had to concern myself with maintenance and rarely even had to put fuel in the planes I rented. All of that was taken care of by the flight schools from which I rented. One school even forbid renters from fueling planes themselves, insisting that it be done by a fuel truck driver. So my plane's tight-then-loose fuel cap was a new thing for me.

One of the important reasons I chose to buy an RV was the incredible help that VAF members provide to others. And I've benefited from that already. Thank you again.