Gas caps - super stiff and almost impossible to get off

Anyone else having this problem with the zenith gas caps?

I've take them apart, lubricated them, adjusted the nut and they are still incredibly stiff and hard to open.

I noticed the tabs were rubbing on the side as you turned to close them. I took a small dremel bit and fixed that but that didn't solve the problem. I tried loosening the nut so they were easy to turn. The next flight they started streaming gas out of both caps during takeoff. That was a fun sight!

So I've learned you can only loosen that nut so much. With the caps snug, I cannot remove them without some kind of fulcrum. I know I am close to busting them.

I also tried sanding the inner round part hoping to reduce the friction but nothing seems to work.

Since these are standard caps that even AS sells, I'm beginning to think I just got a bad batch.

Before I send the money to buy replacrmentsi thought I would check to see if anyone had any suggestions?

Fyi - the rubber gaskets look new and are not worn.

Tia
Gary

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Permalink Reply by David Krakowsky on June 26, 2017 at 11:18am
Gary
My caps were hard to turn also
You need to get some lubrication in the mechanism, and as you observed you have to find a happy medium between too tight and too loose.
Permalink Reply by Gary Welch on June 26, 2017 at 12:08pm
I've tried silicone spray while they were disassembled. That didn't work. I tried some oil lubricant and that didn't help.

After that I wiped al the lube off, and surprisingly that seemed to help a bit. Still don't like the way they are. It's only a matter of time before I bust one.

Fortunately I'm located at the same airport as Quality Sport Planes so I'll check with Doug Dugger. I'm sure he'll have the right answer.

He wasn't around yesterday when I was trying to solve the problem.
Permalink Reply by Brad Rawls on June 26, 2017 at 8:09pm

Gary -

I had the exact same problem. The caps fit fine at first, but then got really hard to turn. I'm using mogas, so I was kind of assuming that was what was causing it.  Are you using Avgas or Mogas? I tried greasing them first, but that did nothing. What I ended up doing is taking the cap apart and then taking a dremel with a sanding drum and run it over the center round tube that everything pivots on, and just thin it down and smooth it up with some fine sandpaper. I works fine like that and the you can tighten the bottom nut so it will still seal the tank.  It's a trail and error fit on the sanding. Not what I would expect for a $50 gas c(r)ap....

Permalink Reply by Gary Welch on June 26, 2017 at 9:07pm

I recently switched over (mostly) to mogas for my O-235.

I just finished doing pretty much what you suggested did and it worked.

Ethanol can clearly cause some plastics to swell. Funny, but I thought I checked every part of my fuel system for ethanol resistance. It never occurred to me to check the fuel caps! 

The only thing I added to your suggestion was to put a bit of EZ Turn lubricant on the stem and plastic seat. EZ Turn is a fuel resistant lubricant and it seemed to help as well.

Thanks for taking the time to help. I appreciate it!

Permalink Reply by Del Clowes on June 27, 2017 at 10:12pm

What carb are you using, any problem there with the mo-gas?

Thanks

del clowes  N364DC

Permalink Reply by Gary Welch on June 28, 2017 at 12:21am

Del;
I'm using the MA-3A carb. I have noticed no difference in the performance compared to Avgas. So far, after about 30 hours of flight time, the only problem with mogas is the gas caps.

Permalink Reply by Del Clowes on June 28, 2017 at 12:20pm

Thanks, I think I'll try with a blend.

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