Your generator may be your only power source during an emergency or power outage. Understanding how it works and determining why your generator won’t start can be the difference you need on a cold winter day when your home loses power.
You can maintain, troubleshoot, and repair your generator with only a few essential hand tools. With proper maintenance, your generator should last a long time and be ready when you need it.
In this article, you’ll learn nine common reasons why your generator won’t start.
Common Generator Starting Problems
Most problems with generator starting are simple to fix:
- Low or old fuel
- Low oil or bad oil sensor
- Choke in wrong position
- Clogged fuel valve or lines
- Clogged carburetor
- Bad spark plug
- Low or dead battery
- Leaving output electrical cords plugged in
- Clogged air filter
Basic Generator Principles
There are several different types of generators:
Troubleshooting techniques differ slightly depending on your generator type, but the basics are similar. Always refer to your owner’s manual or the manufacturer for specifics on your model.
Troubleshooting to Find the Problem
Our troubleshooting centers on gas-powered generators, but many common starting problems apply to all three types.
Internal combustion engines work using spark ignition or compression ignition. Troubleshooting begins with steps that ensure ignition.
1. Check the Fuel Level and Condition
Most people check and replenish the fuel level as part of their starting procedure. This is also the first step in the troubleshooting process. In addition to the fuel level, you should also be aware of the condition of your fuel. Gasoline and diesel fuels degrade over time.
When you store your generator for long periods, the fuel can destabilize. Many manufacturers recommend using a product such as StaBil Fuel Stabilizer. Fuel stabilizers are also available for diesel engines.
If you’ve determined that your fuel level and condition are good, you can move on to the next step.
2. Check for Low Oil or a Bad Oil Sensor
All engines use oil for lubrication. Check your OEM manual to determine the oil requirements for your specific model. If your generator has an adequate oil supply, the problem might be a bad oil sensor.
We found an excellent video demonstrating troubleshooting and repair procedures for several issues we are discussing. You will find it at the end of this article. It’s a longer video, but it’ll be a big help if you’ve never performed these tasks yourself.
3. Check the Choke Lever Position
When cold-starting your generator, the choke lever should be in the “closed” position. When the engine starts, you will move the lever to the “run” or “open” position. The choke lever can remain in the “run” position if the engine is warm.
4. Check the Fuel Valve and Fuel Lines
If the fuel level and condition are good, you can move to the fuel lines and valve. The fuel valve controls the fuel flow to the carburetor. Your owner’s manual can help you locate the fuel valve.
The fuel valve should be “open,” and you should be able to observe the flow of fuel. If you don’t see fuel flow, check if there is a vacuum-relief valve. Open the relief valve or remove the fuel cap to release the tank vacuum. You will need to remove the outlet hose end and place it in a small, clean container. Fuel should flow freely.
Some models have an in-line fuel filter on the outlet hose. Changing or cleaning the fuel filter may fix the problem if fuel flow is obstructed. It is time to check the carburetor if you have adequate fuel flow.
5. Check the Carburetor
Carburetors can become clogged with bad fuel or debris. To check the fuel, drain the bowl assembly using the drain at the bottom into a clean container and examine the fuel. You can remove the bowl and clean it if necessary. Use a carburetor cleaning product and ensure all residue is dry before reassembling the unit.
While you have the bowl off, check the small brass needle and accessible components for debris. Here’s a helpful video detailing the process for replacing the carburetor assembly.
6. Check the Spark Plug
To check the spark plug, you’ll need to remove it. You can use an electronic device to see if the plug is receiving current. The process for this quick check is in the video posted below. You can also test the spark by connecting the plug to the wire and holding the plug against the engine crankcase while pulling the starting cord.
If you see blue sparks, your plug and ignition coil is good. If the spark is weak, check the wire without the plug in the same manner. You should replace the spark plug if you see a strong blue spark. If you see no sparks, you should replace the coil wire.
You can clean deposits off the spark plug using a small knife or a piece of sandpaper. You should use a spark plug gapping tool to ensure the plug has the proper gap. It is best to use a spark plug socket when removing and replacing a spark plug. These protect the ceramic body of the plug during servicing.
7. Check the Battery
If your generator has an electric starter, the problem may be a low battery. Use a multimeter to verify the voltage of the battery. If your battery has cells, check the electrolyte level in all cells. Use gloves to remove the caps carefully and a battery hydrometer to test the electrolyte.
If any cells are low on fluid, use distilled water to refill them to the proper level. You can use a trickle charger if the voltage is low. If the battery doesn’t take and hold a charge, you should replace it with a new, fully charged battery.
8. Make Sure All Electrical Cords Are Unplugged
You should never attempt to start your generator with any electronic items plugged in. This includes restarting your generator after a fueling pause. Start the generator and allow it to reach operating temperature before placing a load on it.
9. Check the Air Filter
Most portable generators use a small foam air filter. This may need cleaning or replacement.
An internal combustion engine must have good airflow to run correctly.
When replacing an air filter, be sure to follow OEM guidelines. Most foam air filters require a light soaking in oil to function their best. This video shows the general procedure for replacing a generator air filter. Your air filter assembly may be slightly different.
The Importance of Preventative Maintenance
Performing preventative maintenance on your generator following OEM guidelines will prepare your equipment. Whether you use your generator as a backup in case of power outages or for auxiliary power while camping, preventative maintenance and periodic starting will ensure it runs well.
You might find answers in this video if you have questions about any of the areas we discussed. You can also leave a comment, and our moderator will forward it to our team.