Six Reasons Your Gas-Powered Generator Won’t Start

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Yet another severe storm has passed through your county, bringing a record amount of rainfall, and bringing down tree limbs and, even, entire trees. A sump pump can help keep your basement from flooding and a portable generator can keep the refrigerator running and the lights on when those tree limbs take out the power lines (as they always seem to do when the wind hits with a little more strength than the average breeze).

As your fail-safe equipment when the power fails, you don’t want your generator failing to start. If you depend on a gasoline-powered generator, the same problems that can prevent a lawn mower, snowblower, or other gas-powered outdoor equipment from starting can keep the generator from doing its job as well. If you’re wondering, “why won’t my generator start?”, let’s go through some common causes.

The generator can’t generate electricity if the generator ‘s engine won’t start

Most gas-powered portable generators rely on a four-cycle engine. Similar to an automobile engine, a four-cycle engine draws gasoline from its fuel tank and has a separate sump for oil. Four-cycle engines may have an electric start feature that allows the engine to be turned over by using an ignition key or a start button, or the operator may need to pull a starter rope to accomplish this.

When the start button is pressed, the ignition key turned, or the rope is pulled, the starter engages the starter cup on the flywheel and rotates the crankshaft. The rotating crankshaft connects to the piston which moves up-and-down within the cylinder and ignition process begins. The flywheel has permanent magnets built into it, and as it rotates past the ignition coil, a magnetic field is created. The magnetic field induces electricity, allowing the ignition coil to send voltage to the spark plug. The piston will travel down the cylinder creating a vacuum that draws fuel and air through the carburetor where they mix before entering the cylinder through an intake port. This action is called the “intake stroke”. Next, the “compression stroke” takes place as the piston travels back up to the top of the cylinder and the intake valve closes. The spark plug now fires and ignites the fuel and air mixture which forces the piston down (known as the “power stroke”). The momentum of the spinning flywheel provides enough force to push the piston back up. The exhaust valve will then open, and the combustion gasses will exit through the muffler in what is the fourth and final cycle – the “exhaust stroke”. A four-cycle engine will continue to run and repeat these four cycles until it is turned off.

6 potential reasons the generator won’t start

To keep the generator’s engine in good condition, you’ll need to perform the same kind of maintenance as you would for your gas-powered lawn mower or snowblower, including changing the oil, replacing the spark plug, and keeping the engine’s carburetor clean. If the generator’s engine won’t start, these are the six most likely reasons why. How to fix a generator that won’t start:

  1. Defective spark plug – Due to carbon build-up or a weakened electrode, a spark plug will degrade over time and be unable to ignite the compressed fuel and air inside the engine’s combustion chamber to start or run the gas-powered generator’s engine. You can use an ignition tester to help determine the strength of the spark plug, but it’s probably easier to simply replace it with a new one, something we recommend doing annually.
  2. Restricted carburetor  –  Old or bad fuel can leave a gummy residue inside the generator’s carburetor creating a restriction. This will prevent the proper ratio of fuel and air from entering the cylinder which can cause the generator engine to have trouble starting. You should always make sure you keep fresh fuel in the tank and use a fuel stabilizer to help preserve its quality. You can try cleaning the carburetor ports with a dedicated carburetor cleaner, or WD-40, to clear out the restriction, but if the clog is particularly bad, you may need to purchase a carburetor rebuild kit to replace some of the components or replace the entire carburetor with a new one when the generator won’t start.
  3. Defective ignition coil – Since the generator ignition coil is designed to send voltage to the spark plug while the engine is running, the spark plug will not be able to ignite the fuel to keep the engine running if the ignition coil is defective. As with the spark plug, you can use an ignition tester to help determine if the coil has failed and requires replacement.
  4. Malfunctioning recoil starter – The recoil starter engages the crankshaft to turn over the engine on engines that utilize a starter rope. A malfunctioning recoil starter may not engage the crankshaft correctly. When the rope is pulled, tabs extending from the pulley and cam should grab the hub of the engine, causing it to turn. When the rope is released, the tabs should retract as the rope rewinds onto the pulley. If the assembly appears damaged or doesn’t function properly, you should replace it with a new one if your generator will not start.
  5. Faulty switch or switches – Either the engine’s start switch, or safety switch (or both), could be faulty. You can use a multimeter to test these switches for electrical continuity – a continuous electrical path present in the switches. The switches should test “positive” for continuity in the “on” position and “negative” for continuity in the “off” position. Be aware that you should get the opposite result for an engine “kill switch” – this kind of switch should test “positive” in the “off” position and “negative” in the “on” position.
  6. Broken flywheel key – The flywheel key is a small metal piece that fits into a slot in the crankshaft and engages with the flywheel. If the generator’s engine stops suddenly, the flywheel key is designed to break in half to prevent damage to the engine. Over time, the key may become worn and break on its own. In either case, the key will need to be replaced with a new one in order for the crankshaft to rotate the flywheel to start and run the engine.

Repair Clinic can ensure your generator will start when your generator won’t start

If your gas generator is not starting, Repair has the genuine manufacturer’s replacement parts you need to ensure your gas-powered generator will start when you need it. But you’ll want to make sure you’re selecting the exact part that works with your generator’s engine. To do this, type the full model number of the generator’s engine into the Repair Clinic website search bar to see a full list of compatible components. You can then use the “Part Category” filter (Examples: “Switch” or “Carburetor”) and the “Part Title” filter (Examples: “Start Switch” or “Carburetor Repair Kit”) to identify the specific part you need. Repair Clinic stocks portable generator engine parts for all the leading brand names, including Black Max, Briggs & Stratton, Cub Cadet, Generac, Homelite, Honda, Husky, Kawasaki, PowerStroke, Ryobi, Toro, Troy-Bilt, and many more. The Repair Clinic website also has “how-to” videos, diagrams, and schematics to assist you in completing the repair yourself, successfully and cost-effectively.

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