| Symptom | Likely Cause | Fix |
| Chainsaw Won’t Start | Ignition off | Turn On |
| Fuel empty | Fill | |
| Choke Off | Turn On | |
| Air filter dirty | Clean | |
| Spark plug foul | Clean | |
| Spark plug poor gap | Gap plug | |
| Fuel contaminated | Drain fuel | |
| Blocked gas filter | Replace | |
| Carburetor dirty | Clean | |
| Carb out of adjustment | Adjust | |
| Spark arrester dirty | Clean | |
| Coil faulty | Test | |
| Ignition system fault | Inspect | |
| Carburetor fault | Inspect | |
| Shear key broken | Inspect | |
| Compression Issue | Test |
| Symptom | Likely Cause | Fix |
| Engine Starts Then Stops | No gas | Fill |
| Bad gas | Drain fuel | |
| Faulty gas cap/vent | Test | |
| Spark plug foul | Clean | |
| Ignition system fault | Inspect | |
| Carburetor dirty | Clean | |
| Carbu gaskets worn | Replace | |
| Carburetor faulty | Inspect | |
| Spark arrester dirty | Clean |
| Symptom | Likely Cause | Fix |
| Engine Won’t Hot Start | Incorrect start procedure | No-choke |
| Coil faulty | Test | |
| Vapour locked | Test | |
| Overheating | Inspect | |
| Flooding | Dry out | |
| Spark plug fouling | Clean | |
| Spark plug poor gap | Gap plug | |
| Piston & bore damage | Inspect |
| Symptom | Likely Cause | Fix |
| Primer Bulb Won’t Fill | Worn diaphragm | Replace |
| Cracked fuel lines | Replace | |
| Perished primer bulb | Replace | |
| Blocked gas filter | Replace |
| Symptom | Likely Cause | Fix |
| Won’t Cut Straight | Chain uneven wear | Replace |
| Bar worn | Replace | |
| Chain Comes Loose | Worn rim drive | Replace |
| Wrong chain pitch | Inspect | |
| Damaged chain | Replace | |
| Worn bar sprocket | Replace | |
| Chain Won’t Oil | Filter blocked | Clean |
| Tank vent blocked | Clean | |
| Bar groove blocked | Clean | |
| Bar oil hole blocked | Clean | |
| Oil line broken | Replace | |
| Chain & Bar Smoking | Oiler not working | Inspect |
| Symptom | Likely Cause | Fix |
| Pull Cord Won’t Catch | Worn pawls | Replace |
| Pull Cord Broken | Cord snapped | Replace |
| Pull Cord Stiff | Engine fault | Inspect |
| Pull Cord Snaps | Shear key broken | Replace |
Symptoms Alphabetically
- About the Author
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John Cunningham is an Automotive Technician and writer at Lawnmowerfixed.com.
He’s been a mechanic for over twenty-five years and shares his know-how and hands-on experience in our DIY repair guides.
Johns’s How-to guides help homeowners fix lawnmowers, tractor mowers, chainsaws, leaf blowers, power washers, generators, snow blowers, and more.