Pressure washers & generators

Generator has fuel problems from old or stale gas

Gasoline degrades within weeks to months, especially ethanol blends, and stale fuel is one of the most common reasons small engines run poorly or won't start after storage.

Difficulty
Easy
Time
20–40 minutes
DIY cost
$10–$25
Pro cost
$80–$180

Symptoms

  • Generator hard to start after sitting unused for a while
  • Runs rough, surges, or stalls easily
  • Fuel smells sour or varnish-like
  • Visible discoloration or separation in the fuel

Likely causes

  • CommonGasoline sitting more than 30 days without stabilizerEthanol-blend gas absorbs moisture and breaks down fairly quickly, forming gummy deposits.
  • CommonCarburetor jets gummed with varnish from evaporated fuelOnce fuel breaks down, sticky residue clogs the fine passages needed for smooth running.
  • PossibleWater contamination in the fuel from condensationPartially filled tanks left for long periods can accumulate condensation, especially with ethanol blends that attract moisture.
  • PossibleFuel line or filter clogged with debris from degraded gasBreakdown products can clog filters and lines, not just the carburetor.

What to do

  1. Drain old fuel into an approved container for proper disposal or recycling; don't pour it down a drain.
  2. Inspect the drained fuel for a sour smell, dark color, or visible separation, which confirms it's gone bad.
  3. Refill with fresh gasoline, using ethanol-free fuel if available for equipment that sits between uses.
  4. Add a fuel stabilizer to any fuel that will sit for more than a few weeks going forward.
  5. Replace the inline fuel filter if the generator has one and it looks discolored or clogged.
  6. If the engine still runs rough after fresh fuel, the carburetor likely has varnish deposits that need cleaning.
  7. For generators used only occasionally, either run the tank dry before storage or always use stabilized fuel to prevent this cycle from repeating.

Tools and parts

  • Approved fuel container
  • Fuel stabilizer
Generator inline fuel filterSearch: “generator inline fuel filter”
Small engine fuel stabilizerSearch: “small engine fuel stabilizer additive”

When to call a pro

If fresh fuel doesn't restore normal running, a small-engine shop can clean varnish deposits from the carburetor.

Safety

Use caution

Handle gasoline outdoors, away from any ignition source, and store or dispose of old fuel properly rather than pouring it out.

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.