One thing that comes from using a generator as your only source of electricity for many years is that you tend to learn a thing or two about fixing common generator problems.
Today, I thought I would share some of the things we have learned over the years with the hope that many of you can benefit from our experience.
There’s nothing more frustrating than a generator that is difficult to start or one that starts but doesn’t run well.
If you’re one of those people who is struggling with a stubborn generator, you’ve come to the right place! Read on and hopefully this article will be able to help you.
Why Generators Can Be Difficult to Start
The main problem with most home generators is that they just don’t get used enough. Most people only use their generator occasionally. Unfortunately, when they put them into storage, they usually leave untreated gasoline in the tank.
Perhaps the most important thing you can learn from this article is that old gas left in a generator’s tank will make your life a living nightmare if you let it stay in there too long.
In just a matter of months, untreated gasoline can leave a thick gooey varnish-like residue in the fuel system. In our experience of dealing with the small engines on generators, it’s this crud that will most often prevent a generator from starting.
3 Essential Things Generator Engines Need to Run
The beginning is usually a good place to start so I’ll start there. All generator engines need three things to run. These three things are listed below:
- Fuel – This can be gasoline, diesel, propane or natural gas.
- Oxygen – The air that your engine needs must be clean so it must always be drawn in through an air filter of some kind.
- Spark – Unless your engine is a diesel, you’ll have one or more spark plugs that ignite the mixture of air and fuel inside the combustion chamber of the engine.
How Generator Engines Work
Before you can figure out why your generator won’t start, you really should understand the basics about how small engines work. I’ve outlined this in a step by step manner to make it simple to understand.
- When you pull on the starter cord, the engine draws air and gas into the carburetor.
- The carburetor mixes the air and gas and sprays a fine mist which is a mixture of air and gas into the combustion chamber.
- The engine’s piton moves to the top of the combustion chamber and compresses this air/fuel mixture.
- When the air/fuel mixture is adequately compressed, the spark plug releases a spark.
- This spark ignites the air/fuel mixture.
- The air/fuel mixture burns very quickly and as it burns it expands. This rapid expansion forces the piston down.
- As the piston is forced down, it rotates the crankshaft of the engine. It’s the crankshaft that it’s connected to the device that actually produces electricity.
- As the piston is moving downwards, it draws in another puff of air and gas.
- When the piston returns to the top of the cylinder head, the entire process repeats itself.
- This cycle continues until the engine either runs out of gas or you move the on/off switch to the off position. This switch is often referred to as a “kill switch” because activating it will kill (or turn off) the engine.
What to Do If Your Generator Won’t Start
Over the years, we’ve helped a lot of people who had problems starting a generator. The following are the list of steps that we would take anytime someone had a stubborn engine that just didn’t want to start.
Check the Gasoline: If the engine won’t start, the first thing we would do is ask how long the gas has been in the tank. Most of the time, the answer is that they can’t remember so the first thing we do is carefully drain the old stale gasoline into a recycle container.
Then we put some fresh gas into the tank. The other thing we do is drain any old stale gasoline from the carburetor float bowl. It won’t do you any good to have fresh gas in the tank if the gas in the float bowl is a mixture of stale gas and water so be sure to drain this as well.
Check the Oil: You may think that low oil wouldn’t prevent an engine from starting but it actually can. If the oil level in your generator is too low, you can cause permanent engine damage by running it without enough oil. What you might not realize is that many modern engines are equipped with what is called a “low oil shutoff sensor”. This sensor is designed to prevent the engine from being damaged by automatically shutting the engine off if the sensor detects that the level of oil is too low.
Make Sure the Fuel Shutoff Valve Isn’t Closed: Believe it or not, this is a common problem that is often overlooked. People often remember that their fuel tank has a shutoff valve and they shut it off before they put it into storage but for some reason they forget all about this valve when they attempt to start it again.
Not all generators will have a shutoff valve but many do so be sure to check to make sure that yours is open. It’s worth pointing out that some generators, like our Honda EU2000i has a shutoff switch on the actual gas cap. If that valve is left in the off position, the generator will run for a few minutes and then it will suddenly stop running. This is because the carburetor isn’t getting any gas.
Make Sure the On/Off Switch Is Turned to the On Position: We currently own three generators and they all have on/off switchs. It would seem like a no-brainer but it’s not uncommon for people to pull and pull on the starter cord only to find out later that they didn’t actually have the switch in the on position.
Make Sure the Choke Is in the Full Choke Position: When you’re starting a generator, you’ll need to put the choke in the full choke position. What this does is restrict the amount of oxygen that passes through the carburetor and increases the amount of gasoline.
With a generator that is functioning properly, a cold engine (meaning an engine that hasn’t been started and warmed up yet) will start with the choke in the full choke position. After a few seconds, it will stall if you leave it in the full choke position. This is because the air to gas mixture is too “rich”. This just means that it’s getting too much gas and not enough air.
With a generator that has a cold engine, you’ll move the lever to full choke, start the engine, let it run for a few seconds, move the choke to the half choke position and then move it to the run position. This means that the choke is wide open and it’s no longer restricting the flow of air into the carburetor.
If the engine will start but it won’t say running, your carburetor probably has an obstruction in the tiny passageways and will most likely need to be cleaned.
It’s been our experience that if the engine will only run in the full or half choke position, it’s quite rare for this problem to fix itself. What you’ll experience is an engine that starts but stalls shortly thereafter or one that will stay running but sounds like it’s surging or stumbling.
Make Sure the Air Filter is Clean: The air filter is essential for preventing damaging dirt and debris from entering the combustion chamber of the engine. It must be in place but if it’s dirty, it won’t let enough air pass through it. This will cause the ratio of gas to air to be incorrect. The mixture will be “rich” so the carburetor will be getting too much gas and not enough air.
Sometimes people try running their engine without an air filter because the filter is too dirty. As mentioned, this can permanently damage the engine so don’t do it. It can also cause the opposite of a “rich” air/fuel mixture. If you try running the engine without an air filter in place, it will be “lean”. This just means that it’s getting too much air and not enough fuel.
If your air filter is dirty and it is the kind that you can clean, follow the instructions in your owner’s manual and clean it properly. If it’s a paper element air filter that isn’t user serviceable, replace it with a new one.
Make Sure the Spark Plug is in Good Condition: Remove the spark plug and make sure that it isn’t “fouled”. A fouled spark plug will have sludge or a lot of heavy dark carbon accumulations. If your spark plug looks bad, replace it with the appropriate plug for your generator’s engine.
While you have the spark plug out, this is a good time to check to make sure that your engine is actually sending electricity to the plug so that it will be able to deliver a spark. The best way to learn how to do that is to look for a YouTube video. Just go to YouTube and type “Check Spark on a Small Engine”.
If your spark plug is in good condition but you don’t actually see a spark when you test it, the reason your generator won’t run is most likely electrical. We’ve only had this problem one time and it ended up being a faulty on/off switch. Once we replaced the switch, we saw spark at the plug and the generator ran great.
The Most Common Generator Starting Problems
Number 1 Most Common Problem – In all our years of dealing with generators that won’t start or run well, the most common issue was that the carburetor was clogged. Unfortunately, this will usually mean that the carburetor needs to be disassembled and properly cleaned. I can’t tell you how many times people have emailed me saying that they removed the air filter and sprayed carburetor cleaner into the carb but their engine still doesn’t run well.
I’ve never actually seen this strategy work, and yes, we have tried it. The reason this doesn’t work is because there are tiny passages that fuel needs to be able to pass through that are usually clogged with varnished fuel. Simply spraying the cleaner into the carburetor won’t clean these passages.
If you’re mechanically inclined, there are tons of good YouTube videos that explain how to clean carburetors. You may even find one that shows you how to clean the carb on the exact model of engine that your generator is equipped with.
If you decide to tackle this job, let me offer some friendly advice. Take lots of pictures of exactly where all the parts were BEFORE you start disassembling them.
A carburetor is a very sensitive part of your engine and it isn’t something that you can “get close enough” when you’re reassembling it. It MUST be reassembled very precisely.
Another bit of advice is to resist the temptation of sticking a wire or small drill bit through the passageways that you’re trying to clean. Do this and you’ll likely have to replace your entire carburetor. Carburetors are made from soft metal and jamming hard metal objects into the tiny passageways will scratch them and they’ll never be the same.
Lastly, don’t spray carb cleaner onto the rubber seals and o-rings inside the carburetor.
Doing so will damage them and they won’t function properly when you reassemble everything.
Number 2 Most Common Problem – The other most common reason that generators won’t start is because the spark plug needs to be replaced. Spark plugs are very inexpensive so I don’t recommend trying to clean them. If you suspect that your spark plug might be bad, replace it. When you do, make sure that you read your engine owner’s manual to find out what the correct gap of the spark plug should be.
You can pick up a simple tool that is designed to make it possible to set the correct spark plug gap for about a dollar at the same store you buy a replacement plug.
Don’t Be Ashamed to Admit When You’re in over Your Head
It’s my sincere hope that this article has been helpful to you. For those of you who feel like you have the necessary mechanical skills to work on your generator, I wish you the best of luck. After all, knowing how to work on our own generators has saved our family a lot of money over the years.
Now, having said that, if you feel like you’re not capable of properly cleaning a carburetor, the best advice I can give you is to swallow your pride and seek help from someone with more experience.
If you’re tired of dealing with horrendously loud generators take a minute and read my article called How to Quiet a Generator to Tolerable Sound Levels.