Chainsaw won't start: Common Causes & How to Fix
1Chainsaw Spark Plug
Most Common Solution
Repair Instructions:
The spark plug itself could be bad. To check, take the plug out and look at it closely. See if the porcelain is cracked, the electrodes are burnt or broken, or there's a lot of carbon buildup. Any of those signs means replace the plug. Even if it looks okay, swap in a new one if it's been a few seasons. Damaged porcelain, electrodes, or carbon mean failure. But plugs also just wear out over time. If it's been a while, a new plug can help even without visible issues. Worn or faulty plugs prevent proper sparking to ignite fuel. Weak or intermittent sparks cause rough running. Replacing worn or damaged plugs ensures strong sparks for smooth operation. Regularly changing plugs keeps things sparking correctly in the combustion chamber.
How to Replace a Chainsaw Spark Plug
- Make sure the chainsaw is turned off and disconnected from power. This is an important safety step. Make sure the chainsaw is unplugged and the stop switch is in the off position before proceeding.
- Locate the spark plug. On most chainsaws, the spark plug is located under the plastic engine cover. Refer to your owner's manual if needed. Remove the engine cover to access the spark plug.
- Remove the old spark plug. Use the socket wrench that came with your chainsaw kit. Place it over the spark plug and turn counter-clockwise to loosen it. Unscrew the old plug completely and pull it out.
- Inspect the old spark plug. Look for damage like cracks or excessive carbon buildup. This can indicate issues with the engine. A wet plug could mean there is too much fuel in the mixture.
- Check the gap of the new plug. Use a feeler gauge tool to measure the gap between the center and side electrodes. Adjust as needed to match the gap specified for your chainsaw model.
- Install the new spark plug. Screw it in clockwise and tighten with the socket wrench. Be careful not to overtighten.
- Replace the engine cover. Make sure all screws and caps are securely in place before reconnecting power.
- Test the chainsaw. Start it up and let it run for a few minutes to ensure everything is functioning properly with the new plug.
2Chainsaw Carburetor
Most Common Solution
Repair Instructions:
The issue could be a clogged-up carburetor. This happens when old gas sits in the chainsaw. Over time, some fuel ingredients evaporate, leaving a thicker, stickier substance. That sticky residue can choke the carburetor and prevent starting. Try cleaning the carb with spray cleaner. If that doesn't work, rebuild or replace the whole carburetor. Letting gas sit turns it thick and gummy. Those deposits block proper fuel flow through the carb. First, spray cleaner into the carb to dissolve built-up gunk. But if old gas was left for too long, the carb may be too clogged internally. Rebuilding or replacing gets fuel flowing correctly again. Removing stale gas and fixing a choked carb can get the engine starting and running smoothly.
How to Replace a Chainsaw Carburetor
- Disconnect the spark plug. Unscrew and remove the spark plug wire to ensure the engine won't accidentally start while working.
- Remove air filter and cover. Take out the air filter and unscrew any caps or covers necessary to access the carburetor. Refer to your model's manual.
- Drain old fuel. Tip the chainsaw to drain any remaining fuel from the gas tank and lines. Catch it in a container.
- Detach fuel lines. Use a small flathead screwdriver to detach the fuel lines from the carburetor inlet and outlet.
- Remove carburetor. Take out any screws securing the carburetor. Carefully remove it from the engine compartment.
- Install new carburetor. Place the new carburetor into position and reattach the screws. Make sure it is seated properly before tightening the screws.
- Reconnect fuel lines. Attach the inlet and outlet fuel lines to the corresponding fittings on the new carburetor.
- Replace air filter and covers. Reattach the air filter, engine cover, and any other caps or covers. Tighten screws securely.
- Add fresh fuel. Fill the gas tank with the fresh fuel mixture recommended for your model.
- Reconnect spark plug. Attach spark plug wire and make sure it is seated firmly.
- Test chainsaw. Start engine and test run to ensure proper functioning. Make adjustments as needed.
3Chainsaw Carburetor Repair Kit
Most Common Solution
Repair Instructions:
The issue could be a clogged up carburetor. This happens when old gas sits in the chainsaw. Over time, some fuel ingredients evaporate, leaving a thicker, stickier substance. That sticky residue can choke the carburetor and prevent starting. Try cleaning the carb with spray cleaner. If that doesn't work, rebuild or replace the whole carburetor. Letting gas sit turns it thick and gummy. Those deposits block proper fuel flow through the carb. First, spray cleaner into the carb to dissolve built-up gunk. But if old gas was left for too long, the carb may be too clogged internally. Rebuilding or replacing gets fuel flowing correctly again. Removing stale gas and fixing a choked carb can get the engine starting and running smoothly.
How to Replace a Chainsaw Carburetor Repair Kit
- Remove the carburetor. Follow steps to detach fuel lines, screws, and carefully remove the carburetor from the chainsaw.
- Disassemble the carburetor. Take apart the carburetor by removing gaskets, needles, nozzle, fuel lines, and any other components that will be replaced in the kit.
- Clean the carburetor. Use carburetor cleaner and small wire brushes to thoroughly clean all components and passages.
- Install new parts from kit. The repair kit should include new gaskets, o-rings, needles, nozzle, and sometimes fuel lines. Carefully replace the old components with new ones.
- Reassemble carburetor. Put all the cleaned components and new parts back together in the proper configuration for your model. Consult the manual for assembly.
- Adjust carburetor. Make proper adjustments to idle speed, fuel/air mixture according to manufacturer specifications.
- Reinstall carburetor. Place the rebuilt carburetor back into the chainsaw and reattach all fuel lines, linkage, and securing screws.
- Replace covers. Put air filter, engine cover, and all other housings back on the chainsaw and secure.
- Test chainsaw. Start the engine and test run the chainsaw to ensure proper functioning. Make any additional tuning as needed.
4Chainsaw Ignition Coil
Common Solution
Repair Instructions:
The ignition coil provides voltage to the spark plug when the engine is running. If it is faulty, the engine may fail to start. Before replacing the coil, check that the spark plug is working right. If the plug is good, use a coil tester tool to test the coil. If it is defective, install a new one. The coil is key for sparking the plug. First ensure the plug itself is not the problem. Then use the tester to check coil operation. The tester sends power through to verify performance. If it is damaged inside, the tester won't read properly. That points to a bad coil needing a swap. But good coil results mean it is working fine.
How to Replace a Chainsaw Ignition Coil
- Disconnect the spark plug. Remove the spark plug wire from the spark plug. This prevents accidental starting.
- Locate the ignition coil. The coil is usually under the flywheel or behind the starter assembly. Consult your owner's manual.
- Remove flywheel or starter. Take off the flywheel nut or starter housing to access the coil.
- Detach wiring. Unplug the ignition coil wires from their connections. There may be 2 or 3 wires.
- Unscrew ignition coil. Remove the mounting screws to detach the coil from the engine housing.
- Install new ignition coil. Screw the new coil into place using the same mounting holes.
- Reconnect wiring. Attach the new coil's wiring to the proper connections. Make sure they are secure.
- Replace flywheel or starter. Tighten the flywheel nut or reassemble the starter housing.
- Reconnect spark plug. Firmly push the spark plug wire onto the spark plug terminal.
- Test chainsaw. Start the engine and let it run for several minutes. Make sure the saw is functioning properly.
- Troubleshoot if needed. If there are issues, recheck all connections and consult the manufacturer's instructions.
5Chainsaw Rewind Spring
Common Solution
Repair Instructions:
When you pull and release the starter rope, a spring recoils it back onto a pulley. If that rewind spring breaks, the rope won't retract onto the chainsaw. So the engine becomes hard or impossible to start up. Replace a broken rewind spring. Many springs can be swapped individually, but replacing the whole recoil starter may be easier. That spring needs to snap the rope back after pulling. Without it recoiling properly, starting is much tougher. Listen when pulling the cord to hear if the spring recoil sounds weak. Visibly inspect the pulley case too for any cracks or damage. If the spring is broken internally, installing a new spring or whole starter gets smooth retraction again.
How to Replace a Chainsaw Rewind Spring
- Remove starter cover. The rewind spring is located under the starter housing. Take off the cover to access it.
- Unhook the recoil spring. Carefully detach the spring from its pulley. Wear gloves and eye protection.
- Take out old spring. Remove any clips or fasteners holding the recoil spring in place. Slide the old spring off its mount.
- Install new spring. Wind the new spring lightly and slide it onto the mount. Reattach any clips or fasteners.
- Attach spring to pulley. Carefully hook the end of the recoil spring to the pulley pivot.
- Wind new spring. Pull the starter rope handle to wind the new spring into starter position. Refer to instructions for proper wind count.
- Test spring tension. Gently pull the starter rope to ensure proper spring tension. The rope should retract smoothly.
- Replace starter cover. Reattach the starter housing cover and tighten all screws securely.
- Connect spark plug. Reconnect the spark plug wire if it was disconnected for safety.
- Test chainsaw. Start the chainsaw and make sure the starter rope retracts properly to confirm the new spring is working.
6Chainsaw Recoil Starter
Common Solution
Repair Instructions:
The recoil starter assembly turns the crankshaft to start the engine. If it's defective, the engine won't crank over so the chainsaw won't start. Remove it and see if it works right. When pulling the rope, tabs on the pulley and cam should grab the engine hub and rotate it. Releasing the rope should make the tabs retract and rewind onto the pulley. Check that full motion when testing the operation. If the assembly isn't engaging and recoiling properly, replace it.
How to Replace a Chainsaw Recoil Starter
- Disconnect spark plug wire. Remove the spark plug wire from the spark plug to prevent accidental starting.
- Remove starter housing. Take out the screws holding the starter cover. Detach the recoil starter housing from the chainsaw.
- Detach recoil spring. Unhook the recoil spring from the pulley and remove it from the starter.
- Remove pulley. Take out the bolt or nut holding the pulley and slide it off the starter rope. Remove the rope from the pulley.
- Detach starter rope. Untie the rope from the handle and pull it out completely from the old starter.
- Install new rope. Feed the new rope through the rebuild kit starter, per the included instructions. Tie it securely to the handle.
- Install pulley. Slide the pulley onto the new starter rope and replace the bolt or nut to hold it in place.
- Reattach recoil spring. Connect the recoil spring to the pulley pivot point.
- Replace starter housing. Position the new starter in the chainsaw and replace the housing cover. Insert and tighten screws.
- Connect spark plug wire. Firmly push the spark plug wire onto the spark plug terminal.
- Test chainsaw. Start the chainsaw and pull the starter rope several times to verify proper operation.
7Chainsaw Recoil Starter Pulley
Common Solution
Repair Instructions:
The recoil starter pulley is what recoils the starter rope when not in use. If the pulley is broken or jammed, it can't retract the rope back in. This will prevent the engine from starting up. If that recoil pulley is damaged, you'll need to replace it completely. The pulley has to be able to smoothly pull the cord back in after it's been pulled out. Anything that stops it from spinning and recoiling will make starting impossible. Check the pulley visually and by pulling the rope to see if the recoil feels weak or rough. If the pulley gets stuck or has broken teeth, it won't work right.
How to Replace a Chainsaw Recoil Starter Pulley
- Remove starter housing. Detach the starter cover to access the pulley inside. Remove any screws or fasteners.
- Disconnect recoil spring. Wear gloves and eye protection. Unhook the recoil spring from the pulley pivot point.
- Remove pulley nut/bolt. Use a wrench to loosen and remove the nut or bolt holding the pulley in place.
- Slide off old pulley. With the bolt/nut removed, you can now slide the pulley off the starter rope.
- Install new pulley. Slide the new pulley onto the starter rope, making sure it is properly aligned.
- Replace pulley bolt/nut. Thread the bolt back into place or tighten the nut securely to hold the new pulley in position.
- Reconnect recoil spring. Carefully hook the end of the recoil spring back onto the pivot point on the new pulley.
- Replace starter housing. Position the starter housing cover back onto the chainsaw. Insert and tighten all screws.
- Test operation. Gently pull the starter rope and let it retract to ensure the pulley and spring are moving smoothly.
- Reconnect spark plug. If disconnected for safety, attach the spark plug wire back onto the terminal.
- Start chainsaw. Start the engine to verify proper pulley and starter operation before regular use.