Your trimmer ran fine last season and now it pulls and pulls without catching, or it fires and dies. Before you buy a new one, run this list. Most no-start problems come down to stale fuel, a fouled spark plug, or a clogged filter or screen, and each one is cheap to fix at home.
1. Replace Old Fuel
Most trimmers run on a gas and oil mix, and that mix goes stale. If the trimmer sat all winter, drain the tank and mix fresh fuel at the ratio printed on the engine or in your manual. Two-stroke engines need the oil mixed in, so do not use plain gasoline.
2. Work the Primer Bulb and Choke
Press the primer bulb until it fills with fuel, as many presses as your manual calls for. Set the choke for a cold start and pull until the engine tries to fire, then move the choke off and pull again. If it floods, leave the choke off, hold the throttle open, and pull several times to clear it.
3. Check the Spark Plug
Pull the plug boot and remove the plug. A wet, black, or crusty tip means it is fouled. Replace it with the plug listed in your manual and set the gap to the manual's spec.
4. Clean the Air Filter
A clogged filter starves the engine of air. Open the cover and tap out dust and debris. Replace a paper filter that is oily or packed, and wash a foam filter if your manual allows it.
5. Check the Spark Arrestor Screen
Many trimmers have a small screen in the muffler that clogs with carbon. A blocked screen makes the engine start and then die or lose power. Let the engine cool, remove the screen following your manual, and clean it with a wire brush or replace it.
6. Inspect the Fuel Lines and Primer Bulb
Old fuel lines crack and the primer bulb can split, which lets air in and keeps fuel from reaching the carburetor. If the bulb never fills, or you see cracks or fuel leaking at a line, replacement kits are inexpensive and match your engine model.
When to Stop and Call Someone
If the fuel is fresh, the plug is new, the filter and screen are clean, and the fuel lines are sound but the trimmer still will not run, the carburetor likely needs a deeper cleaning or rebuild. On an older trimmer, a rebuild can cost close to the price of a new one, so compare before you commit.
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FAQ
Why will my weed eater not start after sitting all winter?
The most common cause is stale fuel. Drain the tank, refill with fresh mixed fuel, and check the spark plug and air filter before anything else.
Why does my string trimmer start and then die?
A clogged spark arrestor screen, a dirty air filter, or a fouled plug are the usual causes. Clean or replace each one in that order.
Do I use pure gasoline in a two-stroke trimmer?
No. Two-stroke trimmers need oil mixed into the fuel at the ratio in your manual. Check the engine label or the manual for your model.
Is it worth repairing an old string trimmer or should I replace it?
If the fix is fuel, a plug, a filter, a screen, or a fuel line, repair it since the parts are cheap. If the carburetor needs a rebuild or the engine has internal damage, compare a repair quote with the price of a new trimmer.