Lawn mower won't start: what to check, in order
Most push mowers that won't start have old fuel, a dirty plug or a gummed-up carburetor. Check the cheap and quick things first, in this order.
Step by step
Checks in order
Safety Pull the wire off the spark plug before you touch the blade or reach under the deck. Wait for the blade to stop completely first.
| 01 | Look in the tank. If the fuel is more than a month or two old, or smells like varnish, drain it and refill with fresh unleaded (no more than 10% ethanol). | Toro calls old fuel the leading cause of hard starting. |
| 02 | Hold the blade control bar against the handle while you pull. Most mowers won't make spark with the bar released. | Never tie the bar down to test. |
| 03 | Use the right starting method for your engine: press the primer 3 times on a Briggs 500E, just pull on ReadyStart and Honda auto-choke engines, set the choke on manual-choke engines. | See your engine page. |
| 04 | Pull the spark plug. If it is wet with fuel, the engine is flooded: dry it, refit it, and try again with the choke off. | |
| 05 | If the plug is black, worn or oily, fit a new one gapped to your engine's spec (table below). | |
| 06 | Check the air filter. A blocked filter can stop a small engine from starting. | |
| 07 | Still nothing with fresh fuel and a good plug? Clean the carburetor float bowl and main jet. | See clean a mower carburetor. |
| 08 | If the pull cord won't turn the engine, something is jamming the blade. Pull the plug wire, tip the mower, and clear the deck. | Check for a bent blade while you are there. |
Plug and starting method by engine
Open the engine or model page for the full parts list.
| Engine | Spark plug | Gap | Starting |
|---|---|---|---|
| Briggs 500E / 550E (09P) | 692051 | 0.020 in | 500E: prime 3 times. 550EX: just pull |
| Briggs 625EXi (093J) | 692051 | 0.020 in | ReadyStart: just pull |
| Briggs 725EXi (104M) | 594056 | 0.030 in | ReadyStart: just pull |
| Honda GCV160 | NGK BPR5ES | 0.70–0.80 mm | Depends on type: choke or auto choke |
| Honda GCV170 | NGK BPR5ES | 0.70–0.80 mm | Auto choke on HRN216: just pull |
| Honda GCV190 | NGK BPR5ES | 0.70–0.80 mm | Depends on type |
Engine not listed?
Send us the model number and we will look at adding it.