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Fuel cap problem

Ed_Wischmeyer

Well Known Member
The tab on one fuel cap has been progressively less willing to stay down. This morning the tab would pop up as if on a spring.

Anybody seen this before? Probably need to replace the O rings, after I look ip the part number.

AvGas only, although I have lubricated the shaft with LPS-2 or maybe WD-40 (yes, I know..)

I did have a spare fuel cap but it was not in my take along kit… fortunately I was at home base when this happened.
 
Most likely, the tab has worn out - the “corner” that causes it to sort of snap into place has become rounded off - happens to all of them after enough use. Generally, by the time that happens, the cap has enough worn parts to be ready for complete replacement, so I don’t know if there are tabs available by themselves. You can disassemble and clean everything up and try it, but my guess is the part is shot.
 
You can remove the roll pin and replace it with a short piece of SS welding rod. I had one that wouldn’t stay completely down and that fixed it.
 
Thanks for the inputs. Just got home and got on Van's website.

The older fuel caps have black O-rings and are no longer available. The newer T-406A... "The brown O-rings are generally auto fuel resistant, but their tolerance for the newer oxygenated auto fuels is unknown." Brown O-rings (the rings themselves) will not fit the earlier black O-ring fuel caps.

I brought home the one that failed and it is a brown, don't know what the other two are.

I don't have any welding rod nor know anybody who does, but I'll look around. I know I have a mess of roll pins, somewhere... saw them just the other day when I was "organizing."

New caps are $65, but there is a backlog at the store and orders take about 10 days to get filled.

Just glad I had a spare...
 
SNIP

I don't have any welding rod nor know anybody who does, but I'll look around. I know I have a mess of roll pins, somewhere... saw them just the other day when I was "organizing."

You can also use the shank of an appropriate sized drill bit. Just cut to length,

Carl
 
Ed,

With a bit of study of the tab on a working gas cap, one can rework the "corner" of the tab to the original shape. This may entail taking a bit of material off the bottom of the tab, but there's plenty of adjustment. Turn over the stainless washer that the corner of the tab rubs on if it's scuffed.

Get new O-Rings from Van's. Lubricate the new O-Rings and shaft with a tiny bit of Krytox™ GPL 205 Grease (Gas won't dissolve it), not Fuel Lube. Put some dry lubricant (that won't attract dirt) on the stainless washer where the corner of the tab runs.

Do not overtighten the lower washer and jam nut. You should be able to open and close the cap with your little finger. Proper adjustment will minimize wear. See instructions from Aircraft Spruce below:
https://www.aircraftspruce.com/catalog/appages/Usher_flushCaps.php?clickkey=7373
 
Paul was right, the cap is worn and there are no replacement parts for it. However, my junk pile had another fuel cap that had a broken roll pin, so that one will be resuscitated and I will still have a spare cap.

It didn't look to me like the worn piece could be reshaped. It had a shoulder worn into it.

While I'm at it, I'll replace the O ring and the large brown O ring, and a spare roll pin and small O ring. Last of the big spenders...
 
Paul was right, the cap is worn and there are no replacement parts for it. However, my junk pile had another fuel cap that had a broken roll pin, so that one will be resuscitated and I will still have a spare cap.

It didn't look to me like the worn piece could be reshaped. It had a shoulder worn into it.

While I'm at it, I'll replace the O ring and the large brown O ring, and a spare roll pin and small O ring. Last of the big spenders...

Be sure to use Krytox lubricant and it will never wash off. Mine stayed buttery smooth for 20 months after sparingly applied. Now I just smear a little at annuals, er, condition inspection.
 
The parts you need are the 33ss latch and post, and o-rings part numbers 50 and 70. Those who have stated the latch gets rounded off are correct.

I was able to order parts in August 2021 by speaking with Lori Robertson at Usher, but...

Last I heard they are not offering to sell individual parts. If you contact the manufacturer, perhaps they would agree if you ordered a descent quantity. I would be happy to go in with you on a group buy if you could arrange it.
 

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