Common Problems With Small Engines
In This Guide
If you own a mower, generator, or snow blower, knowing the common small engine problems saves you money and worry, because the same handful of faults cause almost everything that goes wrong. The headline is that fuel is behind most of it. Stale gas and the gummed carburetor it leaves behind cause more no starts than every other cause combined. Here are the faults you will actually meet, ranked by how often they happen, and how serious each one is.
The Faults You Will Actually Meet
| Problem | How common | Difficulty |
|---|---|---|
| Stale fuel / gummed carburetor | Very common | Easy to moderate |
| Dirty air filter | Common | Easy |
| Fouled or worn spark plug | Common | Easy |
| Old or low oil | Common | Easy |
| Clogged fuel line or filter | Occasional | Easy |
| Bad primer bulb or fuel cap vent | Occasional | Easy |
| Low compression / worn engine | Less common | Hard |
Why Fuel Causes Most of It
Small engines run a few weeks or months a year and then sit. Fuel left in the tank breaks down, especially with ethanol, and forms varnish that clogs the tiny carburetor passages. The engine then cannot draw fuel and will not start or runs rough.
This one mechanism, stale fuel gumming the carburetor, is the root of most small engine trouble. Solve your fuel habits and you eliminate most problems before they start.
The Easy Fixes You Can Do
Drain old fuel and refill with fresh gas.
Replace or clean the air filter.
Swap the spark plug and set the gap.
Change the oil and check the level.
Clear or replace a clogged fuel line or filter.
When It Is More Than Fuel
If fresh fuel, a clean filter, a new plug, and clean oil do not fix it, the issue may be a deeply gummed carburetor that needs a proper clean, or, less often, low compression from a worn engine. Compression problems are where repair costs climb.
A quick way to narrow it down: if the engine has spark and fuel but still will not start, suspect the carburetor first, then compression.
Preventing the Common Problems
Nearly every common fault is prevented by fuel management. Use fresh, ethanol free or stabilized fuel, and never store a machine on untreated gas over the off season. That single habit prevents most of the repairs on this page.
Rather Have a Real Technician Handle It?
A Wildwood technician comes to your driveway, diagnoses the machine on site, and gets it running, usually in about an hour. More than 10,000 repairs completed since 2019, with flat rates quoted before we arrive so there are no surprises.