Gasoline Small Engine will not start/run

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Be sure the engine is fully switched off before looking for blockages or obstructions! 
If you cannot turn the engine from the recoil, or with the electric starter, begin to look for obstructions or blockages in the blades or any other type of attachment which the engine turns.

If your Engine will turn a full revolution by hand with no obstruction to the engine, please follow these tips. If there is an obstruction and the engine will not turn over with a good amount of effort, please contact us below.

1. First be sure you have enough oil in the Engine. If oil is to the top and it still won’t start or shuts itself down after a short time, disconnect the wire from the oil sensor to the Oil Sensor CDI and try running the unit. This is usually a yellow or black wire protruding from the engine above the oil filler. If you get a spark, with this wire removed, it means that the Oil Sensor CDI needs replacing. Do not run the engine for prolonged periods of time without the Oil Sensor CDI attached. This device protects your engine from catastrophic failure, in the event the oil gets low or the pressure drops. This inexpensive part could save your engine from a very expensive repair!

2. Remove the spark plug from the engine and re-attach to the Ignition HT Lead. Hold the end of the spark plug tip to a metal section of the engine, and turn over or crank the engine (you might need a friend to help if your generator does not have electric start). If all is working correctly, you should see a strong spark, and the engine should run smoothly. Not getting a spark? Then you need to replace your Ignition Coil. 

3. Replace fuel with fresh fuel and check the fuel tank does not have any rust as this will enter the head and cause damage. Drain a bit into a glass and inspect to be sure. Replace rusted Fuel Tanks as soon as possible as the contaminants will damage your engine.

4. Check if fuel is getting to the head, by checking if the spark plug is wet, after cranking the engine.

If the spark plug is dry: 

  • If your unit has a Pump, check this is working correctly.
  • Remove your Carb and clean, replace and try starting the generator. 
  • Rebuild it with a Carb Repair Kit (if available for your model). 
  • If this does not fix the problem you will need to replace the Carb. The high Ethanol content in fuel these days can eat away the carb housing and turn to a “varnish” which blocks the internal fuel system.


5. Service the Engine. This fixes most running problems as you should Service your Engine as instructed in your manual. Change all filters, oil and inspect the air filter closely. The foam of the filters has a tenancy to break up and get pulled into the head. To give you an idea of how important regular services are, running your generator for 1 hour is the equivalent of you driving 70 miles. Full-Service Kits are available for most Small Engine.

If you had removed the Carb or adjusted the settings on the Carb then there are a few more thing you need to check.

A) Be sure the Air mixture screw is set correctly. The Air Mixture Screw is the brass screw with a spring behind it on the side of the Carb. On the vast majority of modern units it is usually set to 1.5 turns from tight.

B) Check the Carb Gaskets are not pinching or split. This will also affect the Air/Fuel mixture. Replace if necessary. We sell these separate from the Full Gasket Kits where possible. Look up “Carb Gaskets” on our parts system to see if we do for your engine.

First we need to know what the issue is with your Small Engines.

Ask Roary

Did this fix the problem?

Spanner Driver Answer

Yes thanks! I fixed the issue.

Spanner Driver Answer

I need to buy parts for repair. Help me find the parts I need.

Spanner Driver Answer

No, I need more advice please.

Spanner Driver Answer

I have a Duel/Tri/LPG model and above advice did not fix the issue.