Common Lawn Mower Problems and How to Fix Them
Most lawn mower problems trace back to fuel, air or a dull blade. A mower that will not start usually has stale fuel, a dirty filter or a tired spark plug. Poor cutting points to a blunt blade or clogged deck, and smoke or stalling often means an oil or air issue. Many faults are quick, cheap fixes.
A lawn mower that suddenly plays up can feel like a breakdown, but the common problems are usually easy to trace. More often than not the machine is fine, and the fault is stale fuel, a clogged filter, a blunt blade or a packed deck that costs little to put right.
Below are the issues owners meet most, with practical fixes for each. Good habits prevent most of them, so this pairs naturally with our guide to lawn mower maintenance, and if a machine is truly worn out, our best lawn mowers roundup can help you replace it well.
Make it safe before you start
Every fix below begins the same way. Before you tip the mower or reach near the blade, remove the danger.
- On a gas mower, pull off the spark plug lead so it cannot fire.
- On a battery mower, take out the battery and safety key.
- Let a hot engine cool, and wear gloves whenever you handle the blade.
Never put your hands under a mower that could start. This one habit prevents the worst garden injuries.
Mower will not start
A no start is the most common complaint, and on a gas mower it nearly always comes down to fuel, air or spark. Work through them in order rather than assuming the worst.
- Fuel: old fuel left over winter gums the carburettor. Drain it, add fresh, and use stabiliser next time.
- Air filter: a clogged filter chokes the engine, so clean or replace it.
- Spark plug: a fouled or worn plug will not fire. Clean it or fit a new one.
On a battery mower, check the pack is charged and seated, the safety key is in, and the underside is clear, since many models refuse to run when the blade is jammed with grass.
Poor or uneven cutting
If the lawn looks ragged, torn or striped with missed strips, the blade and deck are the first suspects. A blunt blade tears rather than slices, leaving pale, frayed tips, while a deck packed with clippings cannot lift the grass to cut it evenly.
Sharpen or replace the blade, clear the underside of the deck, and make sure the cutting height is set level. Cutting when the grass is dry helps too, and mowing a little more often keeps each cut short and clean, as we explain in how often you should mow your lawn.
Smoke, stalling or rough running
Smoke from a gas mower looks alarming but is usually minor. White or blue smoke often means oil has reached the wrong place, commonly after overfilling the oil or tipping the machine the wrong way, and it normally clears as it burns off.
Stalling and rough running point to air or fuel starvation. Check the air filter, make sure the fuel is fresh, and see that the deck is not so clogged that it bogs the engine down. If the mower dies under load in thick grass, raise the cutting height and take a narrower bite, then drop it once the lawn is under control.
Starter cord and other niggles
A pull cord that will not retract or feels jammed is often a blade clogged with grass, so make the mower safe and clear the underside first. If the cord itself is frayed or the recoil spring has failed, that is a low cost part to replace.
- Vibration: usually a blade that is loose, bent or unevenly sharpened. Check and balance it.
- Self propel not driving: often a slipped or worn drive belt or cable that needs adjusting.
- Wheels dragging: clear grass and grit from the axles and height adjusters.
When to repair and when to replace
Blades, filters, plugs, belts and cords are wear parts, and replacing them is normal and usually cheap. If the engine or motor is sound, these small fixes can give a mower many more seasons for very little outlay.
Consider replacing the whole machine when the engine burns oil heavily, the deck is rusted through, or repairs would come close to the cost of a new mower. If yours has reached that point, our roundup of the best lawn mowers and wider Outdoors & Garden guides can help you choose a dependable replacement.
Ready to pick one?
If a repair no longer makes sense, our top picks cover reliable mowers for every size of lawn.
Frequently asked questions
Why will my lawn mower not start?
On a gas mower it is nearly always fuel, air or spark. Drain stale fuel and add fresh, clean or replace the air filter, and check the spark plug. On a battery mower, confirm the pack is charged and seated, the safety key is in, and the deck is clear of jammed grass.
Why is my mower cutting unevenly?
Usually a blunt blade or a deck packed with clippings. Sharpen or replace the blade, clear the underside, and set the cutting height level. Mowing when the grass is dry, and a little more often, also keeps each cut short, clean and even.
Why is my lawn mower smoking?
White or blue smoke on a gas mower usually means oil reached the wrong place, often from overfilling or tipping the machine the wrong way, and it normally burns off. Persistent heavy smoke can point to worn engine parts, which is a bigger repair to weigh up.
Why does my mower keep stalling?
Stalling points to air or fuel starvation, or an engine bogged down in thick grass. Check the air filter, make sure the fuel is fresh, and clear the deck. In tall grass, raise the cutting height and take a narrower bite until the lawn is under control.
Why does my mower vibrate?
Vibration is usually a blade problem: loose, bent, or sharpened unevenly so it no longer balances. Make the mower safe, then check the blade is tight, straight and level. A wobbling blade wears the engine bearings, so it is worth sorting promptly.
Is it worth repairing a lawn mower?
Often yes. Blades, filters, plugs, belts and cords are cheap wear parts, and if the engine or motor is sound these fixes restore the machine. Replace the whole mower only when the engine burns oil heavily, the deck is rusted through, or repairs near the cost of new.
How do I stop my mower from clogging?
Mow when the grass is dry, keep the blade sharp, and clear the deck regularly. Cutting a little more often so you remove less each time also helps, since long, wet clippings are what pack under the deck and choke the airflow the mower needs to cut.