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Changing fuel cap o-ring

E

Earl Findlay

Active Member
I need to change the fuel cap brown o-rings on my new to me RV-9. How do I get the old o-ring off, and what?s the best way to get the new one on?

My current o-rings have gotten sticky to the touch. I guess they?re starting to decay so I figure it?s time to replace them.
 
Are you sure they are going bad. The sticky might just be fuel lube, used to lubricate them to make it easier to remove the caps from the tank.
 
The "fuel lube" or EZ-Turn stuff is extremely sticky, but it seals the cap up nicely. The O-rings just slip off with a pick. Rub some on with your fingers (and good luck washing this stuff off), and slip the O-ring back on. I do this at every annual and the O-rings seem to be holding up just fine after 5 years of flying.
 
Remove the nut and disassemble them. There are two O-rings. The big one, and a small one on the stem.
Do not use fuel lube. Use Krytox GPL 205 grease - this is coming from someone who used fuel lube for yeas and use to swear by it.
 
If any of you think it is time to change the O-ring on your fuel cap, then it is probably time to change the on all your quick drains as well. (Both tanks and the gascolator, if installed.)
 
To the OP's question, carefully use a small screwdriver or similar flat tool and lift out the o ring. Get under it and stretch it over the bottom end of the cap. Put some lube in the grove and reinstall a new one by stretching it and rolling over the bottom lip.

Chapstick works nicely as a lube for all parts of the cap.
 
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Agree with the above.
Krytox is the stuff.

Disassemble, clean and reassemble. I did mine and a friend's, and it makes a world of difference.
 
Amazon

While reading, I opened another browser page and ordered Krytox on Amazon. $20 and I will be a popular guy in the hangar row... since I will share with all the RV's that want to clean up their o rings. I have been using fuel lube and it does not lube.... and does not come off my pants.... and is sticky in winter. Enough already, done with you!
 
DC-4 (Down Corning #4) is also good stuff to use on these, and is good stuff for oil filters as well. Fuel lube of similar is the wrong stuff to use. I used it for years until I got wise to DC-4.
 
flightlogic said:
While reading, I opened another browser page and ordered Krytox on Amazon. $20 and I will be a popular guy in the hangar row... since I will share with all the RV's that want to clean up their o rings. I have been using fuel lube and it does not lube.... and does not come off my pants.... and is sticky in winter. Enough already, done with you!
Click to expand...

These ae the same reasons I switched, plus, I always had to work my cams to get them off. I also was using too much force to close the tab. Switching to the Krytox without making any adjustment and now then glide in and out smoothly. The tabs open and close with a finger instead of needing a bottle opener.
 
A finger dipped in avgas and run around the o-ring when refueling has been working for twenty years on my RV-6.......the cap needs to be adjusted properly.
 
Clean Cap

Best to clean the cap completely. Must use extreme care when unscrewing the bottom from the shaft. Small roll pin is easy to break.

If you try to break the nut loose by holding the tab, you will break the small pin. Best to cushion channel lock jaws to hold the top edge of the cap when breaking the nut loose.

If you need any lube at all, your caps are probably sticking due to corrosion inside the cap. Small shaft, under the tab and small metal pad, needs replaced it helps stop water from getting into the internals.

Easiest way to open cap: lift the tab and then push directly down on the shaft top. Cap comes right out! No need for lube when it works right. (This info came from someone posting on a different thread.-it works great!)

Best regards,
Mike Bauer
 
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So if one were going to change to something other than fuel lube, how do you remove the old fuel lube from the cap?
 
Greg-

When I did it last year that was the hardest part.
I soaked everything in Coleman fuel for a while, then spent a lot of time with rags and brushes removing old crud.

New o rings might be easier!
 
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