Generator Tune-Up Checklist: Before Storm Season

Why seasonal maintenance matters

A generator that has sat for months may not start when a storm knocks out power. Fuel degrades, oil breaks down, spark plugs foul, and batteries lose their charge. A seasonal tune-up is the time to catch these issues, not when you are standing in the dark. The U.S. Consumer Product Safety Commission (CPSC) reports that more than 100 deaths each year are linked to portable generators, mostly from carbon monoxide poisoning when generators are run indoors or too close to the home.

Your generator is a piece of emergency equipment. Like a fire extinguisher or a smoke alarm, it needs to work on demand. A tune-up before storm season gives you confidence it will start, run, and produce power safely. Set aside an hour on a dry, well-ventilated day to go through the checklist below.

Gather your tools and safety gear

Before you touch anything, collect the supplies you will need: engine oil (check the recommended viscosity and capacity in your owner's manual), a spark plug wrench, a new spark plug if the old one is worn, a new air filter, fuel stabilizer, a funnel, shop rags, and a battery charger or maintainer. Also have a carbon monoxide alarm with fresh batteries ready for the test run.

Safety comes first. Work in a well-ventilated area, let the engine cool completely before you begin, and disconnect the battery if you are working near electrical components. Never run the generator indoors or in a garage, even with the door open, because carbon monoxide accumulates quickly and can be fatal. CPSC states that one generator produces as much carbon monoxide as hundreds of cars.

Oil: change and check

Engine oil is the lifeblood of your generator. Over time, oil breaks down and collects contaminants. If the oil level is low or the oil looks dark and gritty, change it. Check the oil level with the dipstick, add oil if needed, and follow the manufacturer's recommended interval from your owner's manual. Many generators need a change after the first 20 to 30 hours of use, then every 50 to 100 hours after that, but check your manual for your specific model.

When you change the oil, warm the engine for a few minutes first (if it is safe to do so outdoors), then drain the old oil into a pan. Replace the drain plug, add fresh oil slowly, and check the level. Dispose of the old oil at a recycling center. If you have an oil drain valve, the job is easier.

Also check the oil for signs of contamination. If the oil looks milky or frothy, that could mean water is getting in, and you should have the engine inspected. See Generator Low Oil Shutdown Sensor and Generator Oil Types for more detail.

Spark plug and ignition

A fouled or worn spark plug is one of the most common reasons a generator will not start. Inspect the spark plug for carbon buildup, cracks, or worn electrodes. If the firing end is coated with black soot or the gap is wider than the spec, replace it. Use a spark plug wrench to remove it gently, and gap the new plug to the manufacturer's specification before installing it.

While you are at it, inspect the spark plug wire and the boot for cracks or corrosion. A damaged wire can cause misfires. Make sure the connection is snug when you reattach it. If your generator uses electronic ignition, there is not much to do beyond checking connections, but if it uses a magneto, the air gap between the flywheel and the coil should be checked. See How to Clean a Generator Spark Arrester Screen for more detail.

Air filter and fuel system

A clogged air filter restricts airflow and makes the engine run rich, which fouls the spark plug and increases fuel consumption. Remove the air filter housing, inspect the filter element, and clean or replace it if it is dirty. Paper filters should be replaced, not cleaned. Foam filters can be washed in a mild detergent and allowed to dry completely before reinstalling, then lightly oiled according to the manufacturer's instructions.

Now inspect the fuel system. Look for cracks, leaks, or soft spots in the fuel line. Check the fuel filter if your generator has one. If the fuel in the tank has been sitting since last season, drain it and refill with fresh fuel. Add a fuel stabilizer designed for small engines to keep the fuel fresh during storage. See Generator Fuel Stabilizers and How to Clean a Generator Carburetor for more detail.

If your generator has a carburetor, check the float bowl for water or varnish. A thorough cleaning of the carburetor passages may be needed if the generator has been stored with fuel in it. If you prefer not to drain the carburetor, run the engine with the fuel valve off until it stalls, which empties the bowl.

Battery and electrical system

If your generator has an electric start, the battery needs attention. Check the battery terminals for corrosion and clean them with a wire brush if needed. Make sure the connections are tight. If the battery is the type that can be refilled, check the electrolyte level and top off with distilled water if necessary.

Use a multimeter to check the battery voltage. A fully charged lead-acid battery should read around 12.6 volts or more. If the voltage is low, charge it with a battery charger or a battery maintainer. If the battery is more than three years old or will not hold a charge, consider replacing it before the season. See Generator Battery Chargers and Generator Battery Maintenance for more.

Also check the generator's electrical system. Look for loose wires, damaged receptacles, and signs of overheating like discolored insulation. You can use a multimeter to verify the output voltage at the receptacle while the engine is running. Make sure the ground fault circuit interrupter (GFCI) outlets, if present, trip and reset properly. Read Generator Outlet Types for more information.

Test run under load

Once the oil, spark plug, air filter, fuel system, and battery are in good shape, it is time for a test run. Set up the generator outdoors, at least 20 feet from any window, door, or vent, with the exhaust facing away from the home, as recommended by the CDC. Install fresh batteries in a carbon monoxide alarm and place it nearby, or use one in the house. Never run a generator inside, even in a garage.

Start the generator and let it warm up for a few minutes. Then plug in a load that draws at least half of the generator's rated wattage, such as a space heater (where safe), a toaster, or a set of work lights. Let it run at that load for 10 to 20 minutes. Watch for stable voltage and frequency, no surges, and no unusual noises. Check that the automatic voltage regulator (AVR) keeps the output steady, and confirm the low-oil shutdown feature works if your generator has one.

This run also confirms that the cooling system, if liquid-cooled, has no leaks, and that the exhaust system is working correctly. If your generator has a CO sensor, test it by following the manufacturer's procedure to confirm it functions. See How to Test a Generator Carbon Monoxide Sensor and How to Load Test a Generator for more.

After the test run, let the generator cool, then either store it with a full tank of treated fuel or drain the fuel system depending on your storage plan.

Safety checklist reminder

While your generator is running, remember the key safety rules from the CPSC and CDC: never operate it indoors or in an enclosed space, keep it at least 20 feet from the home with the exhaust pointing away, and have working carbon monoxide alarms on every level of your home. Carbon monoxide is odorless and colorless, and it can make you pass out and die before you notice symptoms.

A generator that is well maintained and used safely is a reliable backup. One that is neglected can be a hazard. This tune-up is the best way to make sure you and your family stay powered and safe through the next storm.

If your generator is due for more extensive maintenance, like valve clearance checks, consider whether you are comfortable doing it yourself or should call a qualified technician. See How to Adjust Generator Valve Clearance for more.

What to pick for your use

Questions

How often should I tune up my generator before storm season?

Do a full tune-up once a year, ideally at the start of the storm season. If your area has a long storm season, check the oil, battery, and test run at the midpoint too.

Do I need to drain the fuel tank before storing the generator?

If you store the generator for more than a month, either drain the fuel system completely or add a fuel stabilizer and run it through the carburetor. This prevents varnish and gum buildup. Read more in the fuel stabilizer guide.

Can I tune up my generator myself?

Most tune-up tasks are simple and require basic tools: changing oil, replacing a spark plug, cleaning the air filter, and checking the battery. If you are not comfortable, a qualified small-engine technician can do it.

What should I do if my generator fails the test run?

If the generator will not start, runs rough, or produces unstable voltage, refer to the troubleshooting guides, check for common issues like a clogged carburetor or a dead battery, and consider professional service.

How far from the house should I run the generator?

The CDC and CPSC recommend at least 20 feet from windows, doors, and vents, with the exhaust pointed away from the home. This is critical to prevent carbon monoxide poisoning.