A mower that will not start does not automatically need a new carburettor or engine. Start by identifying whether you have a petrol, battery or mains-powered mower, then follow the checks appropriate to your model. This guide focuses on petrol mowers and helps you decide when a replacement part may be needed.
First, check the basics
Make sure you are using the mower's normal starting procedure and that its safety controls are correctly engaged. For petrol engines, check the manufacturer's instructions for the correct fuel and starting settings. If the machine has been stored for a long time, old fuel may be part of the problem.
Before inspecting components, allow the engine to cool and follow the manufacturer's instructions to prevent accidental starting. Never work on a running engine or around moving blades.
1. Is there fresh, suitable petrol?
Petrol can deteriorate during storage, and fuel suitability varies by engine. Consult your manual for the approved fuel and storage guidance. If you suspect contaminated or stale petrol, follow the manufacturer's safe procedure for handling it rather than continuing to attempt starts.
2. Could the air filter be blocked?
An excessively dirty air filter may restrict airflow and affect engine operation. Locate the filter using the manual and inspect it as directed. Some types can be cleaned; others must be replaced. Match any replacement to the exact engine model.
3. Is the spark plug due for inspection?
A damaged, fouled or incorrectly specified spark plug can make starting difficult. The engine manual will identify the correct plug and inspection procedure. Do not guess the plug type, gap or tightening
specification. If you are not confident working with ignition components, seek help.
4. Could fuel delivery be restricted?
Some petrol mowers have a serviceable fuel filter, while others have a different fuel-system arrangement. A restriction may cause poor running or starting difficulties, but the symptoms do not prove the filter is at fault. Check our guide to changing a lawn mower fuel filter before ordering a replacement.
5. What if the engine turns over but will not run?
If the starter operates but the engine does not fire, several fuel, air or ignition faults are possible. Avoid repeatedly replacing parts without confirming the cause. The Briggs & Stratton troubleshooting video already on this page provides a useful introduction for relevant engine models.
6. What if the starter will not turn the engine?
Stop if the starter jams, the blade is obstructed or the machine makes unusual noises. Do not put your hands near the blade until the machine has been safely isolated according to the manual. Starting-system and mechanical faults may require a qualified repairer.
Find the correct spare parts
Once you know which component needs attention, identify the mower make and model and, for engine parts, the separate engine model and specification. Use our interactive parts diagrams to confirm the part number. You can also browse our engine service kits, which contain model-specific maintenance items. Check the contents and compatibility before ordering.
If you are unsure which part is suitable, use Contact Us and send the machine and engine details, any existing part number and a photograph of the identification plate. We would rather help you check than have you order the wrong part.
Browse Briggs & Stratton engine service kits
Frequently asked questions
Why will my lawn mower not start after winter?
Old fuel, a discharged battery on electric-start models or a maintenance issue may be involved. Start with the storage and starting guidance for your specific machine.
Does a mower that will not start need a new spark plug?
Not always. A spark plug is one possible cause, but the fuel system, air supply and safety controls also need consideration. Inspect and diagnose before replacing it.
Can a blocked air filter stop a mower starting?
A severely restricted air filter can affect engine operation. Check the manufacturer's inspection and replacement instructions before deciding it is the cause.
Should I replace the carburettor?
Not without diagnosis. Carburettor problems can resemble faults elsewhere in the fuel system. A qualified technician may be needed to identify the problem safely.
How do I know which service kit fits my mower?
Match the kit to the engine identification, not just the mower brand. Check the product listing and ask us for help if any detail is uncertain.
