Gas mower won't start at all

Symptoms

• Pulling the cord (or turning the key) does nothing or feels normal but engine never fires
• No sound of the engine trying to catch
• Worked fine last time it was used
• Mower sat unused for weeks or months

Likely causes

• CommonStale or old gasolineGas older than 30 days loses volatility and won't ignite well, especially after winter storage.
• CommonFouled or worn spark plugA plug coated in carbon or oil won't spark reliably.
• CommonSafety bail lever not heldMost walk-behind mowers won't start unless the handle bar (deadman lever) is held against the handle.
• PossibleClogged carburetorOld fuel leaves varnish that blocks small carburetor passages.
• PossibleBad or dirty air filterA clogged filter can starve the engine of air needed to start.

What to do

1. Check the fuel: if it's more than a month old or smells sour, drain it and add fresh gasoline.
2. Hold the safety bail bar against the upper handle while pulling the starter cord; the engine won't fire without it.
3. Make sure the choke is set correctly: closed/full choke for a cold start, open once running.
4. Pull the starter cord firmly several times, at least 4–6 pulls, to see if it tries to catch.
5. Remove the spark plug, check for fouling or a wet/oily tip, clean or replace it, and confirm the gap is correct.
6. Check that the spark plug wire is firmly connected.
7. If it still won't start, the carburetor may need cleaning; this is a good point to consider a small engine shop.

Tools and parts

• Spark plug socket or wrench
• Fresh gasoline
• Rag

When to call a pro

If fresh fuel and a new plug don't fix it, a small engine repair shop can clean the carburetor and check compression.

Safety