I have a two stroke trimmer with a plastic fuel tank and plastic fuel lines. At some point, these lines have been replaced with new lines that don't quite fit in the holes the old lines did (~0.5mm too small). The main fuel line is a friction fit, while the primer line connects to a plastic barb.

The main fuel line is submerged in the fuel tank, while the primer line connects to the highest point on the tank. It would appear that this fuel system is reliant on an air-tight seal to operate.

I have been unable to locate suitable replacement lines for this trimmer (as it is now rather old).

I would like to seal around the point where the fuel line enters the tank, but have had some trouble finding a suitable product. I have effectively been searching for a fuel resistant silicone.

This product seems as though it might do the job, but it is marketed as a gasket sealant. In my mind, this means it is reliant on being sandwiched between two surfaces. Could I use this product to make an effective repair? Should I choose another product (available in AU)? Should I explore another method?

  • Welcome to Motor Vehicle Maintenance & Repair! – Pᴀᴜʟsᴛᴇʀ2 May 7 at 1:10
  • Does the fuel pipe go into the tank via a hole in the tank and it relies on sealing on the outside of the pipe? – HandyHowie May 7 at 15:42
  • Yep. Seemed to rely on fiction between the pipe and tank. Dribbles fuel on the rare occasion it runs – toxicantidote May 9 at 8:57
  • Followed the fuel line to the intake. It appears to simply deposit the fuel on a sponge so the engine runs on fumes. – toxicantidote May 12 at 1:26

Explore another method. The sealant may work, but it's only a stop gap measure. You're right it needs to be airtight. Any leaks will cause it not to run (it will suck air instead of fuel).

I've got three suggestions for you:

  1. Use very small (thin) zip ties to seal the line against the barb.
  2. Heat the line up (via flame) which will effectively shrink the tubing and will hopefully seal it against the fittings.
  3. Look up the OEM fuel lines for your trimmer.

If you take the second method, you're going to want to ensure there's no fuel present (obviously), or you'll just end up buying a new trimmer.

  • re #2: Not the same scale, but, back in the days of metal gas tanks on cars, we had a nominally empty one we were going to patch. (Solder the seam, probably.) My father took it in the cellar to wash it off, and there were enough fumes left so the water heater pilot set them off. It was pretty loud, though there was no structural damage, and he only had singed eyebrows. So, take care with that flame. – George May 7 at 2:18
  • @George standard practice to solder or weld gas tanks was to fill them with water, leaving just the smallest area around the place to be welded free of water. If it was a long seam then done in sections... – Solar Mike May 7 at 5:36
  • The barbed entry isn't that bad and would be easily fixed by a zip tie. The friction fit is the bigger problem. Without OEM lines, I'll likely look at 3D printing a barb for the friction fit to close the gap, and connecting the fuel line on either end of it. – toxicantidote May 12 at 1:24

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