Is there a fuel cap opening tool?

[toto]

Every 1-2 years at annual, my shop replaces the O-rings on my fuel caps. They’re always functioning perfectly before they’re replaced, and after they’re replaced they’re very tight and nearly impossible to open. This means that line crew are often using things like metal screwdrivers to pry the flange up so they can open them. 

I sometimes try to find a plastic- or wood-handled tool to open them, but I certainly can’t do it with my fingers. 

Anyway… is there a fuel cap opening tool out there that works for this sort of thing?

My paint is in good shape, and I get chills every time I think about a giant metal screwdriver being stuck in the fuel cap and braced on the wing paint during fueling. 

[MikeOH]

I've never had that issue after several different A&Ps have replaced my fuel cap O-rings at annual. Doesn't seem like they are adjusted properly.

[DonMuncy]

The adjustment for the fuel caps is a bit of a trade-off; tight enough to keep water out, and loose enough to open without a tool, but I think your A&P is a little on the tight side. It is not hard for a reasonably talented hangar elf to adjust it.

[toto]

Interesting, thanks both. 

This happens so regularly that I just assumed it was par for the course, and I had to accept a few months of very tight caps after annual. 

[kortopates]

Interesting, thanks both. 
This happens so regularly that I just assumed it was par for the course, and I had to accept a few months of very tight caps after annual. 

No! if it’s too tight right after they replaced o-rings it’s to tight! If it becomes too tight a few months later after being parked on the ramp the inner shaft needs lubricating. Some triflow will correct it or even some motor oil off the dip stick for lack of anything else.


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[Shadrach]

1 hour ago, toto said:

Every 1-2 years at annual, my shop replaces the O-rings on my fuel caps. They’re always functioning perfectly before they’re replaced, and after they’re replaced they’re very tight and nearly impossible to open. This means that line crew are often using things like metal screwdrivers to pry the flange up so they can open them. 

I sometimes try to find a plastic- or wood-handled tool to open them, but I certainly can’t do it with my fingers. 

Anyway… is there a fuel cap opening tool out there that works for this sort of thing?

My paint is in good shape, and I get chills every time I think about a giant metal screwdriver being stuck in the fuel cap and braced on the wing paint during fueling. 

I believe the nut holding the assembly together is pinned. Which means the installer’s options for fine tuning the tension are limited by the notches in the castellated nut aligning with the pin.

try backing the nut off one notch.

[Fly Boomer]

1 hour ago, toto said:

Interesting, thanks both. 

This happens so regularly that I just assumed it was par for the course, and I had to accept a few months of very tight caps after annual. 

Another thing that might help:

https://www.marshbrothersaviation.com/collections/mooney/products/shaw-aero-fuel-cap-washers

[PT20J]

Get the blue fluorosilicone o-rings. They don’t deteriorate rapidly and so don’t require replacement. Mine are 6 years old and look like new and pass the pressure test and the caps are easy to open and I never have to adjust them. I lubricate the caps at every oil change: Vasoline on the big ring; Triflow on the shaft to lube the small one. 

Skip

[toto]

I ended up ordering one of these, just to have it.

For three bucks, it seemed worth having. 

https://bullerent.com/product/fuel-cap-opener/

[toto]

19 minutes ago, PT20J said:

Get the blue fluorosilicone o-rings.

Is this a particular brand?

[tmo]

@OSUAV8TER makes and sells them. Good stuff.

[EricJ]

33 minutes ago, toto said:

Is this a particular brand?

No, fluorosilicone is a material, like nitrile.   It's blue, and if you just look around for fluorosilicone o-rings of the proper size you'll be good.   Aircraft spruce and the usual places have them.   

[pkellercfii]

Agree with Don Muncy that a reasonably skilled hangar elf can readjust fuel cap tension to something more reasonable. It’s just a matter of loosening the nut at the bottom of the cap. You’ll need to replace the cotter pin on the nut afterwards. 
 

After purchasing my Mooney I had the same problem with the fuel caps being set too tight. A plastic bicycle tire lever will do a good job of unsecuring excessively tight fuel caps without marring the paint. I think I still keep one of those levers in my on-board tool kit.

 

—Paul Keller

 

[Fly Boomer]

1 hour ago, PT20J said:

Mine are 6 years old and look like new and pass the pressure test

How do you get 0.5 PSI air to test them?

[LANCECASPER]

1 hour ago, toto said:

I ended up ordering one of these, just to have it.

For three bucks, it seemed worth having. 

https://bullerent.com/product/fuel-cap-opener/

If it's too hard to open it's not set up correctly. The cotter pin needs to be changed out and the castle nut needs to be backed off at least once opening. You do not want to beak off that tab with a tool. There are no new replacement parts available on the Shaw fuel caps.

[PT20J]

1 hour ago, Fly Boomer said:

How do you get 0.5 PSI air to test them?

Get a length of vinyl hose that fits snuggly over the vent and blow into it with your lungs. 

[cbarry]

Just the thought of a fueler prying the latch up, with who knows what, is enough to make a Mooniac cringe!  It makes me think of the fueler pretending to be a bartender practicing popping tops on your Mooney’s fuel caps!  With good seals and proper adjustment, the caps’ latches should not be an ordeal to open/close or require any prying tools.

[Bartman]

Even though mine are adjusted properly, I have still on occasion had to pry it open with a screwdriver wrapped with a cleaning rag.  Not often, but sometimes the line guys don't get the cap on properly and it is not flush.  I try to be present when the fueling is done, but sometimes it is just not practical for whatever reason.

[Skates97]

On 8/26/2023 at 9:55 AM, Shadrach said:

I believe the nut holding the assembly together is pinned. Which means the installer’s options for fine tuning the tension are limited by the notches in the castellated nut aligning with the pin.

try backing the nut off one notch.

A thin washer or two under the nut can help with fine tuning if lining up the hole for the cotter pin won't work. 

[Shadrach]

5 hours ago, Bartman said:

Even though mine are adjusted properly, I have still on occasion had to pry it open with a screwdriver wrapped with a cleaning rag.  Not often, but sometimes the line guys don't get the cap on properly and it is not flush.  I try to be present when the fueling is done, but sometimes it is just not practical for whatever reason.

This has happened to me a few times. This is why I am very particular about who fuels my plane.

[N201MKTurbo]

I always tell then to leave the caps off if I’m there. Some can’t help them selves and feel driven to put them on. Some seem insulted that I think they can’t do it properly. It seems they are somewhat cockeyed about 40% of the time and completely jammed about 5% of the time. I can just imagine what is going through their mind… “Boy, these caps are really jacked up, they take a huge amount of force to close. That guy should get them fixed”

[Bartman]

2 hours ago, N201MKTurbo said:

I always tell then to leave the caps off if I’m there. Some can’t help them selves and feel driven to put them on. Some seem insulted that I think they can’t do it properly. It seems they are somewhat cockeyed about 40% of the time and completely jammed about 5% of the time. I can just imagine what is going through their mind… “Boy, these caps are really jacked up, they take a huge amount of force to close. That guy should get them fixed”

Exactly

[Yetti]

Yep there is seated and then there is the properly aligned with possibly a little jiggle to seat the cap properly.   You might try getting them flush and seated properly.   The o-ring does not squish down that much.

[Echo]

Yes. Back in day made these:

[Gone]

I use the screwdriver bit on the end of my fuel tester. 

It is like the one shown here but mine has a metal probe for the drain valve.  It appears it is not sold anymore with the metal probe.