Fuel Leaking From Tank or Lines: Causes & Fixes

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Overview

Fuel leaks are a safety hazard and should be addressed immediately. Most leaks come from cracked tanks, deteriorated fuel lines, loose clamps, or faulty fittings. This guide explains the most common leak points and how to diagnose them safely.

1. Cracked or Damaged Fuel Tank

Plastic fuel tanks can crack from age, vibration, or impact.

  • Hairline cracks: Often appear around seams or mounting points.
  • UV damage: Causes brittleness and small fractures.
  • Fuel seepage: Leaves wet spots or strong odor around the tank.

2. Brittle or Cracked Fuel Lines (Most Common Cause)

Fuel lines harden and crack over time, especially with ethanol-blended gasoline.

  • Surface cracks: Cause slow seepage.
  • Full splits: Lead to steady dripping.
  • Loose or missing clamps: Allow fuel to leak at connection points.

3. Faulty Fuel Shutoff Valve

Some equipment includes a manual shutoff valve that can leak when worn or cracked.

  • Leaking around the stem: Indicates internal seal failure.
  • Cracked housing: Causes steady dripping.
  • Loose fittings: Allow fuel to escape under vibration.

4. Tank Grommet or Fuel Pickup Leaks

Many small engines use a rubber grommet where the fuel line enters the tank.

  • Deteriorated grommet: Causes fuel to pool under the tank.
  • Loose pickup tube: Allows fuel to leak around the opening.

5. Primer Bulb or Carburetor Inlet Leaks

Fuel may appear to leak from the tank but actually originates from the primer system or carburetor.

  • Cracked primer bulb: Leaks when pressed.
  • Loose carburetor inlet fitting: Allows fuel to drip down the engine.

6. Step-by-Step Diagnostic Flow

  1. Wipe the tank and lines clean to identify fresh leaks.
  2. Inspect the tank for cracks, especially around seams and mounts.
  3. Check fuel lines for brittleness, cracks, or loose clamps.
  4. Inspect the shutoff valve and fittings for wetness.
  5. Examine the tank grommet and pickup tube for seepage.
  6. Check the primer bulb and carburetor inlet for leaks.

Internal Resources

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External Resources

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