My Cruzer fuel tanks have the (I assume standard) Newton SPRL fuel filler neck.  Installing the neck is tricky as it approaches the wing skin — the flange sits tight against the surface, and using a metal wrench risks scratching the flange or skin. I searched for a purpose‑built tool and only found a mention of a custom wrench on a Glasair builders forum, which confirmed I wasn’t the only one facing this problem. That inspired me to design and 3D print this solution.

If your project uses the same screw-in filler neck, this wrench may be helpful for your build as well.

The wrench is modeled directly from measurements of the SPRL cap and fits perfectly inside the filler neck, allowing you to safely tighten it all the way down to the wing skin without risking scratches. My first prototype had a longer handle, which interfered with clecoes on the top wing skin, and made it too easy to apply excessive torque — so use reasonable force during installation to avoid thread damage.

Here is a link to the 3D print files (and a short video of it being used) on MakerWorld: Fuel Filler Neck Wrench for SPRL Cap - Free 3D Print Model - MakerW...

If you want me to print one for you, DM me.  I don't plan to make a business out of this, but if you don't have access to a printer and are in the US, I'll try to work something out with you.

Also, I'd appreciate any feedback on this.  It's the first time I'm publishing my own 3D printed tool.  It's working well for me so far, but I'm not sure how well it will work for others.