Fix for Broken Gas Cap Tether / Lanyard (3D Printed)




Introduction: Fix for Broken Gas Cap Tether / Lanyard (3D Printed)

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After purchasing my new Subaru Impreza I was like probably everyone who ever purchased a new car. . . don't park within 50 feet of ANYTHING, vacuum daily, wash weekly, no leaning on the car, defiantly no food in the car. It has been a few years and most of that has changed, but the first thing to break on my car, still haunts me. It wasn't something major and the car still works fine, but the gas cap tether just hangs there now, limp and broken. Plus I have to be careful not to scratch the car with the broken tether.

I looked into fixing it and found that Subaru didn’t sell just the tether for the gas cap, you have to buy a whole new gas cap! Not that I am against spending another $24.95 on my car, but all I really wanted was the $2.00 tether. I didn’t need one bad enough to buy a new gas cap and have ended up just living with it.

I have, like so many other Subaru owners, just left the broken piece on my precious car for far too long. But not any more! As the powers of 3D printing unite I now have a new gas cap tether. My car is whole again and I can go back to the OCD of shiny car syndrome all over again.


Step 1: Own/Borrow/Rent 3-D Printer

I am one of the lucky few that have access to a 3D printer. Not my own, but my husband's. And if I ask really nicely he even lets me use it. Lets get this straight, I am not technology stupid, but some days my Google-foo is stronger than other days. And since to-date I have "broke" more electronic equipment than he has, I don't actually get to touch the printer. Watch, set up, work with him, that I can do, but touch - NO.

If you don't own a 3D printer, there are some local hot spots (Makerspace) that will let you use them for a small fee, usually inside their own facility. This print took all of about 35 minutes, so you don't always need to rent the printer for a week to finish the smallest of processes. If you are renting one, I recommend the following:

1. Finding out in advance what format your file needs to be in.

2. The bed size and print size. This will make a big difference. The tail of the tether I made was 21-1/2 cm, (about 8-1/2 in) and the ring is 77mm (about 3 in). Since the bed on our printer is 9", we had to curve the tether. This was done in the design process. More on that later.

3. What material you can print. We printed in TPU (flexible filament) but there are so many options.

Step 2: Remove Old Broken Tether

1. Remove the gas cap from the filler neck and use your fingers to pry the tether ring out of the retaining groove on the gas cap. Work your way around the cap, it should come off pretty easily. You could cut it off, but that would make measuring it in the next step a little harder. Put the tether ring somewhere you won’t lose it and replace the gas cap back into the filler neck.

2. Using your fingers again gently pry out the plastic pin that holds the tether tail to the gas door. The hole in the gas door is not perfectly round, try rotating the pin if you’re having trouble getting it out without damage. This part will be re-used so go slow!

If you break it I am sure you can purchase it from the dealership, but this is exactly what we are trying to avoid. That or you can write the next instructable, on how to 3D print the pin.

3. Remove the plastic pin from the gas cap tether tail. Keep the pin somewhere you won’t lose it and put the tail with the ring.

Step 3: Measure the Tether

Break out your ruler and calipers and start measuring the old tether. Inner diameter, outer diameter, thickness and overall length are the critical dimensions to pay attention to. Pictures are worth a thousand words.

Step 4: Create a Model of the Tether

Now what we have measurements we can make a quick model that will get turned into the 3D printed part. Fire up your CAD platform of choice and start sketching. We used OnShape, which is a great program similar to SolidWorks, but has a free option. Any CAD platform will work.

Once you’re happy with the model export it as a .STL file. Attached in the zip file is the .STL file we used.

Step 5: 3D Print the New Gas Cap Tether

This is really my favorite part. The rest resembles some form of work, this is where the magic happens.

Filament loading, bed leveling and other printer preparation is outside the scope of this instructable since it varies so much from printer to printer.

Take the .STL file created in the last step and load it into your favorite printer software. We used Makerware Desktop for this project. If you don't know what software to use, your MakerSpace can help you.

Our printer settings (these will vary a ton from printer to printer, this is what worked for me for this part):

  • Filament material: 1.75mm Blue TPU
  • Layer height: .3mm
  • Infill: 100%
  • Print speed: 30mm/s for all print moves. 150mm/s travel moves.
  • Retraction settings: 4.5mm, 30mm/s
  • Extrusion temp: 220 degrees C
  • Bed temp: 60 degrees C
  • Bed prep: Alcohol wipe only. No tape, hairspray or gluestick needed.

Get your printer setup and ready to go. Load the file you created from the .STL and then watch your part come to life! Magic wands, fairy dust and . . . Abracadabra happy car part!

Step 6: Install the New Gas Cap Tether

Now that the awesomeness has passed, time to get back to business.

1. Remove the new tether from the printer. Look at it with astonishment, take a few pictures, think "oh yeah I did that". Then move on.

2.Go back to the car and remove the gas cap from the filler neck.

3. Slip the new tether into the retaining groove on the gas cap. Note that the fat part of the tether should point down when the gas cap is installed. After you did this incorrectly, remove the tether, flip it over and install correctly.

4. Slide the plastic tether tail pin through the tail of the gas cap tether.

5. Secure the tether tail to the gas door by pushing the plastic pin back into the hole it came out of. That is the top left on my car in case you didn't take a picture before hand.

6. Make sure the new tether doesn’t bind on anything.

7. Enjoy no longer misplacing your gas cap when you fill up!

Step 7: When I Do It Again / Stuff to Know. . .


This Instructable is specifically for a 2010 Subaru Impreza. Reading online this looks like a somewhat common problem for the 2007-2011 Subaru Impreza. Hopefully this helps a few people out there with the same problem. If you don’t have an Impreza the steps to create a gas cap tether / lanyard like this for different cars would be very similar.

I chose flexible TPU filament since the gas cap ring needed to stretch a little to get into the retaining groove on the gas cap and since the tether will bend a little every time the gas door is closed. I haven’t tried any other materials, ABS might work, PLA would probably be too brittle.

The big end of the tether is a little loose, but not really loose enough to let the gas cap fall out. I’m still using it without issue. I’ve tightened up the ID of the big hole by 2mm on the .STL that’s attached here.

How does TPU hold up? So far so good, 1 day in and still there. I even plan to fill up my car tomorrow. All I’m expecting it to do is keep the gas cap attached to the car and not spontaneously combust!

Super turbo official test results:

Bending cycle testing – No noticeable deterioration after 3.4 minutes of mild to vigorous bending action.

Tensile strength testing – It didn’t break when I used it as part of our dog’s leash. But she didn't really like it.

Chemical resistance – Outsourced to an independent resource.

*Independent resource, Googleit, results “it remains stable, but could exhibit slight swelling and may have a decrease in tear resistance with long term exposure to hydrocarbons.”

**Further analysis of the results of independent testing - If your gas cap area is swimming in gasoline you probably have bigger automotive problems than a broken gas cap tether.

And after successfully printing 3 copies, the chances that next time I will actually be able to touch the printer. . . NO!

Step 8: UPDATE 7/10/2017

Many people have asked how the material holds up over time. I had mine installed on my car for over 580 days (Since Sept 2015)! Removed only a few months ago as we are trying out a new model.

I am happy to say it was still working GREAT and showed no signed of issues. This lasted longer than the original Subaru lanyard that came with my 2010 car when it was new off the lot. It was printed out of 1.75mm Blue TPU as you know from above. There seems to be no issues with gas splatter, melting, hot/cold weather conditions or closing the door on the lanyard/breakage. Still very flexible and sturdy! 3D printing is AWESOME.

Step 9: Gold Star for Me

I finally got to use the 3D Printer, and ironically it was for a Gas Cap Lanyard! This instructable was posted Sept 24, 2015, TWO YEARS later and my husband is out of town and we need to print version two lanyard.

So, last night, I fired up the Flashforge, changed the filament that was loaded, pulled up the file on the SD card and printed 4 beautiful version 2 gas cap lanyards. We only needed 1, but I was on a roll. :-) I am so proud of myself.

If you are curious the version 2 lanyard is a new version of the replacement lanyard that has an integrated pin. You no longer have to re-use the old pin on the gas door. Check out, where they are available for purchase:

Oh and honey, the printer is just fine - Gold Star for me!

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6 years ago

Thanks for posting this. 3D printing needs to be appreciated for its ability to produce useful objects with low cost and low material usage, without the need for gigantic injection molding runs. The last thing we need in this world is more useless plastic crap!


Reply 5 years ago

Thanks for your kind words. There are so many great things we can make with 3D printing. It isn't all toys and trinkets - but i must admit I like those too.


7 years ago on Introduction

FYI, put gas in the car today, so I finally really got to use it for its intended purpose! Feels AMAZING knowing that I made it, it works and it looks cool. Wow am I ever easily amused :-) I hope I am not the only that is just thrilled over making things.


7 years ago

I like the color, looks kind of like the Subaru world rally blue!


Reply 7 years ago

I thought the same thing.


7 years ago

Thanks for the ible it was very informative.. Maybe next time u can touch it :)


Reply 7 years ago

We will see. Still learning. It is a lot of fun!