Thermos Style Pressure Fuel Cap failure

[GraemeSmith]

Aircraft Spruce call it a - Thermos Style Pressure Fuel Cap

Manufacturer Shaw Plugs call it a "SnapTite"

Part number 51019-4....2 inch

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Strong smell of fuel in cockpit after fueling. Traced out whole fuel system from tank through firewall and vent system. No leaks. Was pretty sure I had not over filled and spilled into the dam around the filler and have it ooze into the cockpit. Smell went away after a little. Hmmm.....

Then I noticed the cap was a little looser when putting in in. Now I am fairly particular about keeping it on the setting and not using the "tighten/loosen" adjustment. But it was loose. Went to dial it tighter. That showed the rubber bung had cracked and failed under the compression plate. That would allow fuel to leak - especially from a full tank.

450 hours in service

Looks Normal

But actually split under the compression plate

[GordonTurner]

One word. Peter Anson. Hmmm. Two words.

Anyway, consider ordering his replacement and put this problem behind you forever.

Gordon

[builderflyer]

One word. Peter Anson. Hmmm. Two words.

Anyway, consider ordering his replacement and put this problem behind you forever.

Gordon

I second Gordon's remarks. Anson's fuel tank cap is one of the nicest additions I've made to my Sonex. Its well worth the cost.

Art,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,Jabiru 3300 #261

[DCASonex]

My original tank cap started getting too hard to properly seal after a couple of years, replaced and got about same life. Made my own cap similar to Peter's about the time he came out with his. Now just replace the O-ring every couple of years. Would also recommend getting Peter's will cost less than repeated purchases of the overgrown wine bottle stoppers.

David A.