Generator Care Generator Troubleshoot

15 Common Reasons Why Generator Won’t Start?

Imagine a day comes, and you’re forced to take your emergency generator out of storage only for it to disappoint you by not starting. When most people face such an issue, they assume the generator is in a huge problem. But it’s not always the case. So, why won’t your generator start?

Your generator won’t start if low on fuel, there is low oil in the crankcase, or the oil sensor is malfunctioning. The unit will also not start if the battery is disconnected or dead, its spark plug is faulty, has carburetor problems, uses a dirty or clogged air filter, the weather is freezing, or a load connected when starting the generator.

Generators are complex power-producing machine with multiple parts working together to ensure it delivers. If one piece malfunctions, the unit will develop problems like not starting. The above are the most common issues why your generator won’t start. Below is an explanation of what causes each of these problems and how you can work your way out of it.

Why is Your Generator Not Starting? Here is why:

Sometime back, before getting into the generator industry, we experienced a blackout in my residence. I rushed to the storage, took my WEN Electric-Start Dual-Fuel generator out, and tried to start it. At first, I tried the ignition switch, but the engine did not start.

I thought the battery was dead. I tried pulling the recoil starter, and nothing worked. I checked for any fuel leaks, but nothing seemed out of place. The first thing that came to mind was that my generator was dead.

The next thing I did was call a local generator technician to come and look at the unit. To my surprise, he changed the air filter and cleaned the spark plug, pushed the ignition key, and my beast was roaring. I paid the technician, but I felt like he robed me.

It’s then that I decided to research all the possible causes, and here is what I found.

1) Disconnected, Low-Charge or Dead Battery

If you’re trying to start the generator with an electric start key, button, or switch and it’s not starting, there is a chance the battery is dead. Typically, most people would try the recoil backup starter if the generator has it and it’s working correctly. If the engine starts, the battery is either disconnected, low on charge, or dead.

Locate the battery using the generator’s manufacturer’s manual and make sure it’s properly connected. Be sure to confirm the polarity of the battery; the red wire should be connecting to the positive terminal and the black or white wire connecting to the negative terminal.

Suppose the battery connection is okay; test for the battery charge with a multimeter. It should be above 10-volts. If lower, use a 12-volt DC battery charger to charge it. If the generator starts with the recoil starter, you don’t need a charger; you can allow it to run for a while to charge the battery.

If it’s a standby generator and there is no way of starting the engine manually, use a battery jump-starter kit to boost the engine starting power. You can also use your car’s battery to start the generator and connect its battery to charge it.

If charging the battery doesn’t add much charge, it is dead and needs a replacement.

2) Faulty Recoil Starter

If the recoil starter mechanism fails, you can try pulling the recoil cord the whole day, and the engine won’t start. You want to make sure you feel the resistance of the engine when trying to start the generator.

There might be a problem if the recoil cord is slack or loose, especially with the flywheel. Open the top recoil starter cover and inspect for anything that’s out of place. You can try to apply some lubrication spray to the spring; they might be stuck open.

Try tying a short-meter-long rope to the start cup and make sure it has a notch to allow you to hook the rope end for leverage when pulling. Pull the cord to see if the generator will start. If it starts, the recoil start assembly is faulty.

3) The generator is Out of Gas

It might seem obvious, but it’s a very common thing to try starting the generator when there is no fuel in the fuel tank, or the propane tank is near empty, especially if you were using the generator a day earlier.

You can start by peeping into the generator fuel tank to see enough gas to start the engine. Some generators come with a fuel gauge on the fuel tank cap, and it can tell you how much fuel is remaining. You can shake the generator genteelly to see if any gasoline of the gauge isn’t working.

If you’re using propane fuel, the tank weight can easily deceive you that there is enough gas in it. You can try tapping on its side; when you hear a different sound, that’s the level of propane in the tank.

You can also pour boiling water on the propane tank from the top down and feel it with your hand; the gas level will start to feel colder.

There is also the use of a magnetic strip for testing propane. You attach it to the propane tank side and pour hot water on it; it will change color to show the remaining gas level.

If you want a more precise method, you could measure the propane tank. When full, it should be 37 pounds and 17 pounds when empty. So, measure the tank weight and subtract to know how much propane is left.

4) Fuel Valve is CLOSED

Even though it seems obvious that the fuel valve should stay on, you might have, or somebody might have closed it. And it can be the cause of why your generator won’t start. If the engine isn’t getting any gasoline, it won’t start.

It won’t cost you anything to check the fuel valve position before retrying to start your generator. You want to keep it at ON or on the arrow mark. If you’re operating a dual-fuel generator, make sure the appropriate valve is open. For the propane tank, you want to make sure the regulator valve is on.

5) Plugged electronics during startup

You MUST never start your generator with the extension cord hooked into the unit’s outlets. You should NOT connect anything to the generator before starting the generator.

When it’s still under load, starting the generator may damage the engine components, including the valves, rotating diodes, exciter windings, voltage regulator, and suppressor.

If any of things were to fail, your generator wouldn’t start, and your mind has a bigger problem that can potentially render your generator useless.

You’re supposed to start the engine and give it some minutes to stabilize before hooking up the electrical loads.

6) Running on Stale Gas

If you store your generator for more than two weeks with fuel in it without treating it with a fuel stabilizer, it’s possible that the fuel has gone bad, and that’s why your generator isn’t starting.

The same could happen if you’re using stored fuel that’s never treated and it’s more than a month old. It would be the same case if the fuel you’re using were treated by old than a year old.

Stale gasoline isn’t flammable anymore. Most of the active ingredients have evaporated, leaving unusable substances that will only cause problems to your generator, one of them being the generator not starting.

Down do you check if the fuel is stale? Open the fuel drain and pour some fuel into a jar. Stale gas has a different color, and it’s a bit cloudy. You can also smell the fuel tank for a varnish-like smell.

If you’ve been using stale fuel to start the generator, drain the fuel and refuel with fresh gasoline. Also, clean the carburetor as the varnish left could cause issues there.

You can run more about proper generator storage here.

7) Generator Engine is Flooded

Your generator might not be starting because its engine is flooded with unburnt fuel or oil. When these unburnt fuel mixtures or oil enter the combustion chamber, they wet the spark plug, preventing sparks.

Generator Engine is Flooded

And as you continue to crank the generator, you’re aggravating the problem. It’d be best to chill out for 5 minutes and try again. One sign of a flooded (hydro locked) engine is, it’s hard to pull the recoil cord.

Read more about this here.

8) Low oil

Another possible reason your generator won’t start is that it has low engine oil. The oil sensor can prevent the generator from starting if the oil level is beneath the acceptable level.

Before starting your generator, check the oil level to make sure it’s ideal. Make sure the generator is on a level surface as you check the level. If the generator is on a slanting spot, the oil sensor might not be floating right, sensing the wrong level.

9) Oil Sensor is Malfunctioning

The oil sensor is one piece that protects the generator engine from running low on oil. All the engine parts rely on the oil to keep them lubricated and prevent wear and tear. It’s also necessary to transfer heat from these parts to the crankcase.

The oil sensor has a float that keeps an eye on the oil level. If it drops to undesired levels, the oil sensor will shut down the generator. And as I mentioned in the previous possible cause, it could also prevent the generator from starting.

The same could happen if the sensor were to fail. If the float got stuck at a lower level than the oil, the generator wouldn’t start.

You can check if the oil sensor is responsible for preventing your generator from starting by disconnecting the connector connecting the two wires into the crankcase from the side. Typically, green and yellow wires.

Try starting the generator with the sensor disconnected. If it starts, the oil sensor is faulty. You can connect it back after the generator start. At times it’ll work. If the generator shuts off, then it’s faulty.

Replacing this part is nearly impossible, and it might be extremely costly as the engine has to come apart. It’s mostly not worth it. You could use the generator without it, but you have to manually prioritize checking the generator oil level, time, and then. As running on low oil could damage your engine and render your generator useless.

10) Faulty Spark Plug

If the generator fuel tank has enough gasoline, the oil sensor is okay, and there is enough oil in the crankcase, and the generator won’t start, there could be an issue with the ignition system, mainly the spark plug.

With time the spark plug can get coated by carbon deposits and prevent it from producing sparks strong enough to start the generator. It could also be that the spark plug gap is wider than usual to the point that they don’t allow the sparks to be produced.

You have to remove it to assess it. Your generator might have come with a spark plug wrench you can use to remove it. If not, find one and remove the spark plug. It’d be easier to replace it with a new one if available. These things are relatively cheap and easily accessible.

If you don’t have a spare, take a soft wire brush or a knife and scrub off any carbon deposits on the spark plug. Also, use a gapping tool to make sure the electrode is gapped right. Refer to your generator’s manual for the ideal gas size for your model.

You can also test the spark plug by pulling the recoil start while holding the plug’s body to the engine’s crankcase. You want to check the strength and color of the spark, with a suitable plug producing strong and blue sparks. If anything less, you’ll have to install a new one.

11) Wrong Choke Lever Positioning

If you’re not into generator operation much, when starting a generator, the chock has to be off and move it to the ON position when the generator starts. Trying to start the generator with the choke on will make it challenging for the engine to start.

Use the generator manual to locate the choke and ensure it’s on the OFF position before pressing the ignition key or pulling the recoil cord. When the generator starts, allow it to warm up before turning it on.

12) Dirty Air Filter

A dirty air filter can also potentially prevent the generator from starting if it’s too dirty to allow the correct amount of air to the carburetor. That’s why it’s always best routine to clean or replace the air filter once in a while.

Use the generator manual to locate your unit’s air filter, generally mounted on the carburetor’s side. Open the top cover to access the air filter cartridge or foam that filters the debris out. How dirty is it?

You can decide to hit the wall to dust it off or clean it with running water, mild dishwasher soap, and running water. If too dirty, consider replacing it with something newer and clean.

13) Clogged or Air Locked Carburetor

A clogged or stuck carburetor can also prevent your carburetor from starting. The carburetor is responsible for ensuring the engine receives the right amount of air-fuel mixture. If the air inlet was stuck open, it’s like you’re trying to start the generator with the choke open. If the carburetor is clogged, the air-fuel mix might not be reaching the engine.

Mainly this issues are caused by varnish produced when gasoline goes bad while in the carburetor. If you previously stored your generator for more than a month with fuel in the carburetor, there’s a chance it went bad and caused varnish to cause the clogging.

The best way to correct this is to remove the carburetor and clean it thoroughly. You could try removing the air filter and spraying some lighter fluid into the carburetor. The carburetor is probably dirty and clogged if the generator starts or the chock valve is open.

Try spraying some carb cleaner to the valve and in the carburetor housing. Give it some minutes to loosen up the varnish gum before trying the generator again. If nothing fruits, shut off the fuel valve and remove the air filter housing and support. Disassemble the carburetor from the generator and set it on a towel laid on a table.

Take it apart and clean all the parts out using a carburetor cleaner. For the fuel jets, try using a thin wire strand to remove anything that might be blocking them.

In the future, you must never store your generator for more than two weeks with fuel in the fuel tank or the fuel line. Drain everything out before storage.

Read more about carburetor cleaning here.

14) Clogged Fuel Line or Valve

Your generator fuel tank might be full and the carburetor clean, but in between, there might be a problem blocking the fuel from flowing freely. The fuel line or valve might be clogged, preventing enough gas from reaching the engine during startup.

It can happen when you use dirty gasoline or when you store your generator with fuel in it. The varnish created when some gasoline additives evaporate can gum up these parts, causing a problem with the fuel flow.

If you did clean the carburetor, but you’re still having issues starting the generator, there might be a blockage in the fuel line.

Before doing anything, confirm the fuel valve and the vacuum relief on the fuel tank cap are open. However, don’t be surprised if yours doesn’t have a vacuum relief. When you confirm the two parts are entirely open, try starting the generator. If nothing improves, don’t be alarmed, you can also try other tricks.

Try unplugging the fuel hose from the inlet side of the fuel valve to monitor the fuel flow. The task can be messy, so it’d be best to have a bucket and some towels to catch the spill out. It should flow out freely. If not, check for any obstruction and its cause.

If the fuel flows well, reconnect the hose to the valve inlet and disconnect the hose connecting to the valve outlet. Open the fuel valve and watch how the fuel flows out. Does it seem obstructed? If so, it’d be best to find a replacement.

If the flow is okay, connect the hose and disconnect from the carburetor. Do the same observation you did earlier. You want to make sure the fuel flows smoothly.

15) Cold Weather Problems

If the weather outside is too cold, it can potentially prevent the generator from starting. The fuel temperature might be too low for the sparks to ignite it.

What you need is a cold-weather kit to help warm the gasoline and increase its lowest ignition temperature. Also, try keeping your generator away from the falling snow.

Related Questions

Can You Refuel a Portable Generator While It’s Running?

NO! You can never refuel your generator while it’s running. You MUST shut it off and allow it to cool down before attempting to refuel it. Gasoline is volatile and highly flammable. The hot engine can potentially create sparks that can ignite the gasoline fumes, causing fire and possibly an explosion.

About the author

Sharif Gen

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