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CanadaFrom mowing the lawn to power washing the deck, warm weather means it’s time to fire up all those small engines that sat idle all winter. If your lawn mower, power washer, weed trimmer, rototiller or other lawn & garden tool won’t start, consult our small engine troubleshooting guide.
Designed to help you diagnose problems with 2- and 4-cycle engines, this guide outlines diagnostic procedures you can use to get your lawn & garden equipment working again. The guide examines the three primary areas necessary for proper operation of any engine: ignition, fuel delivery and mechanical functions.
Step 1: Check your ignition system.
Keep an eye for:
- Faulty ignition switch
- Broken, damaged or corroded wire
- Timing
- Improper spark plug gap
- Faulty ignition coil
- Faulty spark plug wire
Be sure to take a close look at your spark plug within the combustion chamber. It's an excellent tool for diagnosing engine problems. Though spark plugs themselves are rarely the cause of the problem, they do interact with fuel delivery, spark delivery and mechanical functions. Examination of the spark plugs can sometimes give a physical clue of the underlying cause.
Step 2: Ensure you have fuel, that it's not contaminated nor stale.
Make sure there's no water in the fuel tank and the octane rating isn't too low.
Step 3: Select your engine concern to understand related causes.
Improper Fuel/Air Ratio
- Inspect choke operation
- Improper carburetor settings/adjustments
- Air leak in intake system
- Damaged head gasket or cracked cylinder/cylinder head
- Leaking crankcase seals
- Engine flooded
- Dirty fuel filter
- Defective fuel pump
Improper Oil or Fuel/Oil Ratios (2-cycle engine only)
- Improper mix
- Separation of oil and fuel
- Main bearing seal leakage
Battery Condition
- Low voltage
- Inadequate charge
- Internal short circuit
- Corrosion
- Poor or loose connections
- Faulty starter
- Lack of battery fluid
Exhaust Restriction
- Damaged exhaust system
- Clogged or restricted baffles or exhaust port
Improper Fuel/Air Ratio
- Inspect choke operation
- Improper carburetor settings/adjustments
- Air leak in intake system
- Damaged head gasket or cracked cylinder/cylinder head
- Leaking crankcase seals
- Engine flooded
- Dirty fuel filter
- Defective fuel pump
No Spark
- Ignition switch off
- Wiring in primary or secondary circuit disconnected, broken or corroded
- Contact breakers stuck or oxidized
- Coil and condenser faulty
- Battery condition
- Ignition module - no signal
- Poor or loose connections
Battery Condition
- Low voltage
- Inadequate charge
- Internal short circuit
- Corrosion
- Poor or loose connections
- Faulty starter
- Lack of battery fluid
Low or Loss of Compression
- Cracked or broken piston rings
- Damaged head gasket or cracked cylinder/cylinder head
- Valve sticking or broken push rod
- Pre-ignition damage
- Detonation damage
Valve Problems (4-cycle engine only)
- Improper adjustment in lash
- Improper seating due to burned, bent or stuck valve
- Broken valve spring
- Valve or valve seal leaking
Improper Fuel/Air Ratio
- Inspect choke operation
- Improper carburetor settings/adjustments
- Air leak in intake system
- Damaged head gasket or cracked cylinder/cylinder head
- Leaking crankcase seals
- Engine flooded
- Dirty fuel filter
- Defective fuel pump
Improper Oil or Fuel/Oil Ratio (2-cycle engine only)
- Improper mix
- Separation of oil and fuel
- Main bearing seal leakage
Battery Condition
- Low voltage
- Inadequate charge
- Internal short circuit
- Corrosion
- Poor or loose connections
- Faulty starter
- Lack of battery fluid
Low or Loss of Compression
- Cracked or broken piston rings
- Damaged head gasket or cracked cylinder/cylinder head
- Valve sticking or broken push rod
- Pre-ignition damage
- Detonation damage
Exhaust Restriction
- Damaged exhaust system
- Clogged or restricted baffles or exhaust port
Valve Problems (4-cycle engine only)
- Improper adjustment in lash
- Improper seating due to burned, bent or stuck valve
- Broken valve spring
- Valve or valve seal leaking
Improper Fuel/Air Ratio
- Inspect choke operation
- Improper carburetor settings/adjustments
- Air leak in intake system
- Damaged head gasket or cracked cylinder/cylinder head
- Leaking crankcase seals
- Engine flooded
- Dirty fuel filter
- Defective fuel pump
Valve Problems (4-cycle engine only)
- Improper adjustment in lash
- Improper seating due to burned, bent or stuck valve
- Broken valve spring
- Valve or valve seal leaking
Improper Fuel/Air Ratio
- Inspect choke operation
- Improper carburetor settings/adjustments
- Air leak in intake system
- Damaged head gasket or cracked cylinder/cylinder head
- Leaking crankcase seals
- Engine flooded
- Dirty fuel filter
- Defective fuel pump
Oil or Fuel/Oil Ratio (2-cycle engine only)
- Improper mix
- Separation of oil and fuel
- Main bearing seal leakage
Cooling (2-cycle engine only)
- Restricted in cooling system or fins
- Lack of coolant
- Cooling fin damage
- Damaged head gasket
Lubrication
- Out of oil
- Improper oil or fuel/oil ratio
Carbon Buildup (2-cycle engine only)
- Normal accumulation
- Excessive rich mixture, fuel/oil ratio
- Incorrect oil type
Faulty Governor
- Governor assembly malfunctioning
- Linkage out of adjustment, worn or disconnected
- Governor spring sensitivity too great
- Linkage binding
Engine Overload
- Engine operated in conditions above those for which designed
Valve Problems (4-cycle engine only)
- Improper adjustment in lash
- Improper seating due to burned, bent or stuck valve
- Broken valve spring
- Valve or valve seal leaking
Improper Fuel/Air Ratio
- Inspect choke operation
- Improper carburetor settings/adjustments
- Air leak in intake system
- Damaged head gasket or cracked cylinder/cylinder head
- Leaking crankcase seals
- Engine flooded
- Dirty fuel filter
- Defective fuel pump
Low or Loss of Compression
- Cracked or broken piston rings
- Damaged head gasket or cracked cylinder/cylinder head
- Valve sticking or broken push rod
- Pre-ignition damage
- Detonation damage
Exhaust Restriction
- Damaged exhaust system
- Clogged or restricted baffles or exhaust port
Valve Problems (4-cycle engine only)
- Improper adjustment in lash
- Improper seating due to burned, bent or stuck valve
- Broken valve spring
- Valve or valve seal leaking
Oil or Fuel/Oil Ratio (2-cycle engine only)
- Improper mix
- Separation of oil and fuel
- Main bearing seal leakage
No Spark
- Ignition switch off
- Wiring in primary or secondary circuit disconnected, broken or corroded
- Contact breakers stuck or oxidized
- Coil and condenser faulty
- Battery condition
- Ignition module - no signal
- Poor or loose connections
Cooling
- Restricted in cooling system or fins
- Lack of coolant
- Cooling fin damage
- Blown head gasket
Lubrication
- Out of oil
- Improper oil or fuel/oil ratio
Low or Loss of Compression
- Cracked or broken piston rings
- Damaged head gasket or cracked cylinder/cylinder head
Valve sticking or broken push rod
- Pre-ignition damage
- Detonation damage
Valve Problems (4-cycle engine only)
- Improper adjustment in lash
- Improper seating due to burned, bent or stuck valve
- Broken valve spring
- Valve or valve seal leaking
Improper Fuel/Air Ratio
- Inspect choke operation
- Improper carburetor settings/adjustments
- Air leak in intake system
- Damaged head gasket or cracked cylinder/cylinder head
- Leaking crankcase seals
- Engine flooded
- Dirty fuel filter
- Defective fuel pump
Improper Oil or Fuel/Oil Ratio (2-cycle engine only)
- Improper mix
- Separation of oil and fuel
- Main bearing seal leakage
Cooling
- Restricted in cooling system or fins
- Lack of coolant
- Cooling fin damage
- Damanged head gasket
Lubrication (2-cycle engine only)
- Out of oil
- Improper oil or fuel/oil ratio
Low or Loss of Compression
- Cracked or broken piston rings
- Damaged head gasket or cracked cylinder/cylinder head
- Valve sticking or broken push rod
- Pre-ignition damage
- Detonation damage
Engine Overload
- Engine operated in conditions above those for which designed
- Valve (4-cycle engine only)
- Improper adjustment in lash
- Improper seating due to burned, bent or stuck valve
- Broken valve spring
- Valve or valve seal leaking
Exhaust Restriction
- Damaged exhaust system
- Clogged or restricted baffles or exhaust port
Improper Fuel/Air Ratio
- Inspect choke operation
- Improper carburetor settings/adjustments
- Air leak in intake system
- Damaged head gasket or cracked cylinder/cylinder head
- Leaking crankcase seals
- Engine flooded
- Dirty fuel filter
- Defective fuel pump
Oil or Fuel/Oil Ratio (2-cycle engine only)
- Improper mix
- Separation of oil and fuel
- Main bearing seal leakage
Cooling (2-cycle engine only)
- Restricted in cooling system or fins
- Lack of coolant
- Cooling fin damage
- Damaged head gasket
Lubrication
- Out of oil
- Improper oil or fuel/oil ratio
Engine Overload
- Engine operated in conditions above those for which designed
Improper Fuel/Air Ratio
- Inspect choke operation
- Improper carburetor settings/adjustments
- Air leak in intake system
- Damaged head gasket or cracked cylinder/cylinder head
- Leaking crankcase seals
- Engine flooded
- Dirty fuel filter
- Defective fuel pump
Faulty Governor
- Governor assembly malfunctioning
- Linkage out of adjustment, worn or disconnected
- Governor spring sensitivity too great
- Linkage binding
Lubrication
- Out of oil
- Improper oil or fuel/oil ratio
Carbon Buildup (2-cycle engine only)
- Normal accumulation
- Excessive rich mixture, fuel/oil ratio
- Incorrect oil type
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