6A Fuel cap question

[dalemaher]

Hi, yesterday I "rebuilt" both of my fuel caps due to a broken roll pin. I ordered all new gaskets and even the main pin / latch assembly. I figured 20 years old, so $40 in parts to rebuild them was money well spent.

I assembled the caps and incrementally tightened the bottom half of the cap and lock nut until the cap would not spin in the tank opening when the latch was in the down / closed position (one of which takes quite a bit of effort to push down).

Today I flew after refuelling, and the result was blue streaks from both fuel caps.

What did I do wrong? Would lube stop the leaking?

[RV8JD]

The instructions call for the use of Fuel Lube, but many now use Krytox GPL 205 grease instead.

Instructions, including adjustment notes:

[RV7 To Go]

+1 for Krytox! Used fuel lube initially and always found it a pain to open and pull the caps out. After cleaning and using the 205 they work smoothly and no issues with sealing when the caps are setup properly. Still working great after about 200 fill ups over the last 2 years. Use it on my tailwheel as well. Got it on Amazon...expensive but worth it.

[dalemaher]

I tried to find Krytox in Canada...not common.

A friend at my airport had some EZ Turn Fuel Lube and it absolutely did the trick. Will try to find Krytox in the future, but either way, the lube is essential when rebuilding the fuel caps!

[Bob Martin]

Originally Posted by RV7 To Go

+1 for Krytox! Used fuel lube initially and always found it a pain to open and pull the caps out. After cleaning and using the 205 they work smoothly and no issues with sealing when the caps are setup properly. Still working great after about 200 fill ups over the last 2 years. Use it on my tailwheel as well. Got it on Amazon...expensive but worth it.

+1 for Krytox

[JimWoo50]

I got tired of messing with the standard caps so spent $130. at Airventure couple years ago and bought locking caps. They are very nice and require no maintenance.

[RV7 To Go]

Originally Posted by dalemaher

I tried to find Krytox in Canada...not common.

A friend at my airport had some EZ Turn Fuel Lube and it absolutely did the trick. Will try to find Krytox in the future, but either way, the lube is essential when rebuilding the fuel caps!

I found it on Amaz...ca a couple years ago. It's more common on eBa..ca. Expensive stuff... $127.00 C for an 8 oz tube at the time. Saw it now for $140. Takes a small amount so it will last. I used EZ Turn initially. It was very sticky and made the caps difficult to open, especially when cold.

[RVDan]

I typically use DC-4 compound. Much cheaper than Krytox and readily available. Relube every annual. Fuel lube is better than nothing but quite stiff when it gets cold.

[gasman]

Originally Posted by dalemaher

Hi, yesterday I "rebuilt" both of my fuel caps due to a broken roll pin. I ordered all new gaskets and even the main pin / latch assembly. I figured 20 years old, so $40 in parts to rebuild them was money well spent.

I assembled the caps and incrementally tightened the bottom half of the cap and lock nut until the cap would not spin in the tank opening when the latch was in the down / closed position (one of which takes quite a bit of effort to push down).

Today I flew after refuelling, and the result was blue streaks from both fuel caps.

What did I do wrong? Would lube stop the leaking?

The O ring must have lube applied so it can slide and expand as the cap is latched. Without it, the caps will be very hard to close. And will be very hard to remove without pushing down on the stem after the tab has been lifted.

[avrojockey]

Originally Posted by dalemaher

Hi, yesterday I "rebuilt" both of my fuel caps due to a broken roll pin. I ordered all new gaskets and even the main pin / latch assembly. I figured 20 years old, so $40 in parts to rebuild them was money well spent.

I assembled the caps and incrementally tightened the bottom half of the cap and lock nut until the cap would not spin in the tank opening when the latch was in the down / closed position (one of which takes quite a bit of effort to push down).

Today I flew after refuelling, and the result was blue streaks from both fuel caps.

What did I do wrong? Would lube stop the leaking?

https://www.amazon.com/Chemours-D124.../dp/B073Y4557Y

+1 for Krytox. Rebuilt my fuel caps a couple months ago and the use of EZ Turn from past owners was noticeable. The problem with EZ turn seems that it makes the o-ring stick to the nylon(?) rings on the fuel cap halves instead of providing a lubricant for the o-ring to "squeeze" out and seal the opening.

With Krytox the o-ring glides on the nylon so it pushes out to a larger O.D. and seals with ease. In fact, when properly lubed you can squeeze the two cap halves together by hand easily, and watch the o-ring squeeze out.