Trimmers, blowers & chainsaws

String trimmer leaking fuel

Fuel leaking from a trimmer usually comes from a cracked fuel line, a loose or damaged fuel cap, or a torn primer bulb. Identifying exactly where the leak starts narrows down the fix quickly.

Difficulty
Moderate
Time
20–40 minutes
DIY cost
$5–$20
Pro cost
$60–$100

Symptoms

  • Fuel smell around the trimmer
  • Visible wet spot near the tank or lines
  • Fuel dripping from the primer bulb
  • Fuel seeping from the cap area

Likely causes

  • CommonCracked primer bulbThe clear rubber primer bulb dries out and cracks with age and sun exposure.
  • CommonDeteriorated fuel linesEthanol fuel breaks down rubber fuel lines over time, causing cracks and leaks.
  • PossibleDamaged fuel cap gasketA worn gasket under the fuel cap no longer seals properly.
  • PossibleCracked fuel tankImpact or age can crack the plastic tank itself.
  • Less commonLoose carburetor fuel line fittingA fitting that has worked loose lets fuel seep at the connection point.

What to do

  1. Stop use immediately and move the trimmer away from any heat or ignition source if you smell fuel.
  2. Let the trimmer sit on a dry surface and visually trace where the wet fuel spot originates.
  3. Inspect the primer bulb for cracks and replace it if compromised, since these are inexpensive and easy to swap.
  4. Check the fuel lines running from the tank to the carburetor for cracking or a soft, swollen texture, and replace if degraded.
  5. Inspect the fuel cap gasket and replace it if it looks flattened or cracked.
  6. Look over the tank itself for stress cracks, especially around the fill neck.
  7. If you can't identify the source or the tank is cracked, take it to a small-engine shop rather than continuing to use a leaking trimmer.

Tools and parts

  • Flashlight
  • Small screwdriver
Primer bulbSearch: “trimmer primer bulb replacement”
Fuel line kitSearch: “small engine fuel line replacement kit”
Fuel capSearch: “trimmer fuel cap replacement”

When to call a pro

If the fuel tank itself is cracked, replacement of the tank assembly is best done by a small-engine repair shop.

Safety

Use caution

Never run or start a trimmer that's actively leaking fuel; move it outdoors away from any spark or flame source until repaired.

Related guides

Operator provides AI-generated troubleshooting information. It can be wrong. For safety-critical, electrical, gas, structural, medical, automotive safety, or other high-risk problems, consult a qualified professional.