Generator Won’t Start (Problems & Solution)

As anyone who has experienced a prolonged power outage knows, generators can be a lifesaver. However, their reliability can often be called into question when they refuse to start.

In this blog, we have covered the most common reasons that your generator won’t start along with the solutions.

without further ado, let’s get started.

Here are the common reasons a generator might not start:

  1. Empty or stale fuel.
  2. Blocked fuel filter.
  3. Faulty spark plug.
  4. Dead battery.
  5. Old or contaminated oil.
  6. Faulty carburetor.
  7. Broken recoil starter.
  8. Air filter blockage.
  9. Faulty ignition coil.
  10. Inadequate compression.
  11. Overload.
  12. Bad fuel cap.
  13. Faulty starter motor.
  14. Choke position error.
  15. Faulty or damaged wiring.

Understanding Generators and Their Function

A generator is a device that converts mechanical energy into electrical energy. It acts as a backup power source, kicking in when your regular power supply goes out. For hospitals, businesses, and even households, the generator’s reliability is essential for maintaining regular activities. When a generator fails to start, it can cause disruption and, in some cases, even be dangerous.

Common Reasons Your Generator Won’t Start

Empty or Stale Fuel

Just like your car, your generator needs fuel to run. If it’s empty or the fuel has gone stale due to long periods of inactivity, the generator won’t start.

Blocked Fuel Filter

A blocked fuel filter can prevent the generator from getting the fuel it needs to run. Regularly checking and replacing your fuel filter can prevent this issue.

Faulty Spark Plug

If your generator’s spark plug is damaged or corroded, it may fail to ignite the fuel-air mixture in the engine, preventing the generator from starting.

faulty spark plug

Dead Battery

Some generators use a battery to start. If your generator’s battery is dead or low, it may fail to start.

Old or Contaminated Oil

Old, dirty, or contaminated oil can cause problems with the operation of your generator. Regular oil changes are important for the longevity and function of your generator.

Faulty Carburetor

The carburetor mixes air and fuel for combustion. If it’s faulty or clogged, the engine may not get the right mixture for combustion, preventing the generator from starting.

Broken Recoil Starter

If your generator uses a recoil starter and it’s broken, the engine won’t turn over. Check the recoil starter for any signs of wear or damage.

Air Filter Blockage

Air filters prevent dust and debris from getting into the engine. A blocked air filter can choke your engine, preventing it from starting.

Faulty Ignition Coil

The ignition coil generates the voltage for the spark plug. A faulty ignition coil means no spark and, consequently, the generator won’t start.

Inadequate Compression

Engines require a certain amount of compression to operate. If your generator’s engine has inadequate compression, it won’t start.


If your generator is overloaded with too many appliances or devices, it may refuse to start. Be aware of the power limits of your generator and try not to exceed them.

Bad Fuel Cap

A malfunctioning fuel cap that doesn’t allow air into the tank can create a vacuum, preventing fuel from reaching the engine.

Faulty Starter Motor

The starter motor turns the engine over to start it. If your starter motor is faulty, your generator won’t start.

Choke Position Error

Improper positioning of the choke can prevent the generator from starting. Ensure the choke is in the correct position when starting.

Faulty or Damaged Wiring

Faulty or damaged wiring can prevent power from reaching where it needs to go, causing the generator to fail to start.

What to do when a generator won’t start?

When your generator won’t start, first, check the fuel level; it might be empty or contain stale fuel. Examine the spark plug for any damages, and ensure the battery is charged. Verify that the oil is not old or contaminated, and inspect the carburetor and recoil starter for faults.

Look for any blockages in the air filter and ensure the ignition coil is functional. The generator might also not start due to inadequate compression or if it’s overloaded, so adjust the load if necessary.

Check the fuel cap for faults and the starter motor for any issues. The choke should be in the correct position, and ensure that the wiring is not faulty or damaged. If these steps don’t work, consider hiring a professional.

Here are some commonly faced issues for portable generators. Let’s have a look.

Generator Stalling During Operations

A generator stalling during operation can disrupt critical processes relying on its power output. Here are some common reasons and their solutions:

1. Overloading:

  • Reason: If too many appliances or systems are drawing power from the generator simultaneously, it can overload the generator and cause it to stall.
  • Solution: Only connect essential appliances or devices to the generator, and ensure their combined power requirements do not exceed the generator’s capacity. Use a power strip with a built-in circuit breaker for added protection.

2. Fuel Issues:

  • Reason: Low fuel levels, old or contaminated fuel, or a clogged fuel filter can cause the generator to stall.
  • Solution: Regularly check the fuel level and the quality of the fuel. Replace the fuel if it’s old or contaminated, and clean or replace the fuel filter as needed.

3. Dirty Air Filter:

  • Reason: If the air filter is clogged, it can prevent the generator from getting the air it needs to run, causing it to stall.
  • Solution: Clean or replace the air filter regularly to ensure the generator can get enough air.

4. Overheating:

  • Reason: Generators can stall if they overheat, which can be caused by poor ventilation, a malfunctioning fan, or low coolant levels.
  • Solution: Make sure the generator is well-ventilated, regularly check the fan for issues, and keep the coolant levels topped up.

5. Inadequate oil levels:

  • Reason: Generators need oil to lubricate their moving parts. If the oil level is too low, it can cause the generator to stall.
  • Solution: Regularly check the oil levels and top up if necessary. Replace the oil entirely as per the manufacturer’s recommended schedule.

6. Carburetor Issues:

  • Reason: If the carburetor is dirty or malfunctioning, it can cause the generator to stall.
  • Solution: Regular maintenance of the carburetor, including cleaning and replacement of components when necessary, can help prevent this issue.

Generator Has Clogged Fuel Lines

If your generator has clogged fuel lines, it can prevent fuel from reaching the engine properly, causing the generator to run poorly or not start at all. Here’s why this may happen and how you can solve it:

Reasons for Clogged Fuel Lines:

  1. Old or Contaminated Fuel: Fuel that’s been sitting in the generator for a long time can get stale and form gummy deposits, which can clog the fuel lines. Also, contaminated fuel often contains debris or water that can lead to clogs.
  2. Lack of Regular Maintenance: Regular maintenance includes checking and cleaning fuel lines. If not done regularly, residues can accumulate over time and lead to clogs.

Solutions for Clogged Fuel Lines:

  1. Drain the Old Fuel: If the fuel is old or contaminated, drain it from the generator. Make sure to dispose of it safely according to your local regulations.
  2. Clean the Fuel Lines: This can often be done by removing the fuel lines and blowing compressed air through them to remove the clog. In some cases, you might need to use a special solvent to dissolve the deposits.
  3. Replace the Fuel Filter: A clogged fuel filter can cause issues similar to a clogged fuel line. If the fuel filter is clogged, replace it.
  4. Use Fresh, High-Quality Fuel: Always use fresh, high-quality fuel for your generator. This can help prevent clogs from forming in the first place.
  5. Regular Maintenance: Regularly check and clean your fuel lines to prevent clogs from forming. This should be a part of your regular generator maintenance routine.

Generator Starts But Shuts Down

A generator that starts but then shuts down can be due to several reasons, some of which are fairly simple to fix, while others might require professional help. Here are some possible causes and solutions:

Reasons for Generator Shutting Down After Starting:

  1. Low Fuel or Oil Levels: If your generator doesn’t have enough fuel or oil, it can shut down shortly after starting.
  2. Blocked Fuel or Air Filter: A clogged fuel filter or air filter can prevent the necessary fuel or air from reaching the engine, causing the generator to shut down.
  3. Overheating: If the generator overheats, it may shut down to prevent damage. This could be due to low coolant levels, a faulty fan, or other issues.
  4. Faulty Sensors or Switches: If the sensors or switches that monitor the generator’s operating conditions are faulty, they might cause the generator to shut down.
  5. Load Exceeds Capacity: If you’re trying to power too many devices and exceed the generator’s capacity, it can cause the generator to shut down.

Solutions for Generator Shutting Down After Starting:

  1. Check Fuel and Oil Levels: Make sure your generator has enough fuel and oil. Refill as necessary.
  2. Clean or Replace Filters: Check the fuel and air filters. If they’re clogged, clean or replace them.
  3. Check for Overheating: If your generator is overheating, check the coolant level and ensure the cooling fan is working properly. If these are not the issues, have a professional inspect the generator.
  4. Inspect Sensors and Switches: If the generator has a self-diagnostic system, check for error codes that could indicate a faulty sensor or switch. If necessary, have these parts replaced.
  5. Manage Power Load: Be mindful of how many devices you’re trying to power at once. If the total power demand exceeds the generator’s capacity, you’ll need to reduce the load.

Generator Runs Unevenly And Then Stalls

A generator running unevenly, often described as “surging,” before stalling, is indicative of underlying problems that can be related to the fuel system, air intake, or electrical components. Here are the potential causes and solutions:

Reasons for Generator Running Unevenly and Stalling:

  1. Dirty or Clogged Fuel System: If the fuel filter or carburetor is dirty or clogged, it can cause irregular fuel flow, leading to uneven running and eventual stalling.
  2. Old or Contaminated Fuel: Fuel that’s been sitting in the tank for a long time, or contaminated fuel, can lead to uneven running as it may not burn as efficiently.
  3. Air Filter Issues: A dirty or clogged air filter can restrict airflow to the engine, causing it to run unevenly.
  4. Spark Plug Issues: A worn-out, dirty, or improperly gapped spark plug can cause the engine to run unevenly and stall.
  5. Electrical Problems: Problems with the generator’s electrical components, such as the alternator or voltage regulator, can cause uneven running.

Solutions for Generator Running Unevenly and Stalling:

  1. Clean the Fuel System: Check the fuel filter and carburetor for dirt and blockages. Cleaning or replacing these parts can improve fuel flow.
  2. Use Fresh Fuel: If the fuel is old or contaminated, drain the tank and replace it with fresh fuel.
  3. Check and Replace Air Filter: Inspect the air filter and clean or replace it if necessary.
  4. Inspect and Replace Spark Plug: Check the spark plug for signs of wear, fouling, or incorrect gapping. If needed, replace it.
  5. Inspect Electrical Components: If you suspect an electrical issue, it might be best to have a professional inspect the generator. They can check the alternator, voltage regulator, and other components to ensure they’re working correctly.

Generator Low on Coolant

Running low on coolant is a common issue that can cause serious problems for your generator, potentially leading to overheating and significant damage. Here’s why this might happen and what you can do about it:

Reasons for Low Coolant:

  1. Leaks: Over time, seals and hoses in your cooling system can wear out and cause leaks.
  2. Insufficient Refilling: If the coolant isn’t refilled to the correct level after being drained, the generator can end up running low on coolant.
  3. Faulty Coolant Sensor: A faulty coolant sensor might not alert you when the coolant is running low, causing the generator to run with insufficient coolant.
  4. Evaporation: Over time, some amount of coolant may evaporate, especially in hot climates, leading to low levels.

Solutions for Low Coolant:

  1. Check for Leaks: Regularly inspect your generator for any signs of leaks. Check the ground under the generator and the coolant hoses and connections for any signs of moisture.
  2. Refill the Coolant: If the coolant is low, refill it to the manufacturer’s recommended level. Be sure to use the type of coolant recommended by the manufacturer.
  3. Replace the Coolant Sensor (if faulty): If you suspect that the coolant sensor is faulty, have it inspected and replaced if necessary. A working sensor will alert you when the coolant level is low, preventing the generator from running without enough coolant.
  4. Regular Maintenance: As part of regular maintenance, check the coolant levels and top off if necessary. This should be done more frequently in hot climates where evaporation can be a significant factor.

Generator Leaking Oil, Fuel, or Coolant

A generator leaking oil, fuel, or coolant is a serious issue that should be addressed promptly to prevent further damage and potential safety risks. Here’s why this might occur and what you can do about it:

Reasons for Leaks:

  1. Worn-Out Seals/Gaskets: Over time, seals and gaskets can wear out and cause leaks. This is especially common in older generators.
  2. Loose Connections: Connections can loosen over time, leading to leaks.
  3. Physical Damage: Damage to the generator’s housing, oil lines, fuel lines, or coolant system can cause leaks.
  4. Overfilling: Overfilling the oil or coolant can cause it to leak.

Solutions for Leaks:

  1. Check Seals/Gaskets: Inspect the seals and gaskets in your generator. If they’re worn out or damaged, replace them.
  2. Tighten Connections: Check all connections for tightness. Loose connections should be tightened, but be careful not to overtighten as this can also cause damage.
  3. Inspect for Physical Damage: Check the generator for any signs of physical damage. If damage is found, it should be repaired. In some cases, parts may need to be replaced.
  4. Correct Oil and Coolant Levels: If you’ve overfilled the oil or coolant, drain the excess until you reach the manufacturer’s recommended level. Be careful when handling these fluids and dispose of them safely.
  5. Regular Maintenance: Regularly inspect your generator for leaks and address any issues as soon as they arise. This can prevent small leaks from turning into bigger problems.

Generator Block heater hose failure

A block heater is a crucial component of a generator, especially in colder climates. It warms the engine to improve starting and reduce mechanical wear in cold weather. Failure of the block heater hose can lead to inefficient warming of the engine and can increase wear and tear on your generator.

Reasons for Block Heater Hose Failure:

  1. Age and Wear: Over time, the heater hose can deteriorate due to continuous exposure to heat and coolant chemicals. This can lead to cracks, leaks, or a complete failure.
  2. Improper Installation: If the heater hose is not installed properly, it can cause premature failure. This includes factors like incorrect routing of the hose, which can lead to chafing against other components.
  3. Freezing Temperatures: If the coolant inside the hose freezes, it can expand and rupture the hose.

Solutions for Block Heater Hose Failure:

  1. Regular Inspections: Periodically inspect the heater hose for signs of wear or damage. This includes looking for cracks, bulges, soft spots, or leaks.
  2. Proper Installation: Ensure the heater hose is installed correctly. If you’re replacing it yourself, follow the manufacturer’s instructions for routing and securing the hose. If you’re uncertain, consider hiring a professional to perform the installation.
  3. Use the Correct Coolant Mixture: Use a mixture of coolant and water that is appropriate for your local climate. This can help prevent the coolant from freezing and causing damage to the hose.
  4. Replace Damaged Hoses: If you find any signs of damage during your inspections, replace the heater hose immediately to prevent further damage or a potential breakdown of the generator. Always use high-quality replacement parts that meet or exceed the manufacturer’s specifications.
  5. Keep Spare Hoses: In case of emergencies, it’s always good to have spare heater hoses that can be used for quick replacements.

Generator Wet Stacking

“Wet stacking” is a condition that can occur in diesel generators when they are operated with a light load for an extended period of time. It results in the buildup of carbon, unburned fuel, lubricating oil, and other substances in the exhaust system, which can affect the generator’s performance and longevity.

Reasons for Wet Stacking:

  1. Running at Low Load: Wet stacking often occurs when a diesel generator is run at a low load (generally less than 30% of its rated capacity) for a prolonged period. This prevents the engine from reaching its optimal operating temperature, causing incomplete combustion of the fuel.
  2. Poor Quality Fuel: Using poor quality fuel can also lead to wet stacking, as it can produce more residue and increase the risk of incomplete combustion.

Solutions for Wet Stacking:

  1. Load Bank Testing: Regular load bank testing, where the generator is run at a high load for a specified period, can help burn off the accumulated deposits and prevent wet stacking.
  2. Correct Load Management: Try to manage the load so that the generator operates closer to its rated capacity. If you typically need only a small amount of power, consider using a smaller generator that can operate at a higher percentage of its rated capacity.
  3. Use High-Quality Fuel: Always use high-quality fuel to reduce the amount of residue and improve combustion efficiency.
  4. Regular Maintenance: Regular maintenance, including cleaning and inspection of the exhaust system, can help identify and address signs of wet stacking before they become serious.
  5. Proper Engine Tuning: Ensuring the engine is tuned properly can improve fuel combustion and reduce the risk of wet stacking.

Generator Fuel Depletion

A generator running out of fuel is a common issue, but it can cause significant disruption, especially during power outages or critical operations. Here’s why this might happen and what you can do about it:

Reasons for Fuel Depletion:

  1. Extended Usage: If a generator is run for an extended period without refueling, it can simply run out of fuel.
  2. Fuel Leaks: Leaks in the fuel system can lead to rapid depletion of fuel.
  3. Poor Fuel Efficiency: If the generator is not maintained properly or is running inefficiently due to mechanical issues, it can consume fuel at a higher-than-normal rate.

Solutions for Fuel Depletion:

  1. Regularly Check Fuel Levels: Regularly check the fuel level in your generator and refill it as necessary. Don’t wait until it’s completely empty to refill, as this can introduce air into the fuel system, making it difficult to restart.
  2. Check for Leaks: Regularly inspect the generator for signs of fuel leaks. If any are found, they should be repaired immediately.
  3. Maintenance and Tuning: Regular maintenance and tuning of the generator can improve its fuel efficiency, allowing it to run longer on the same amount of fuel. This includes tasks like changing the oil, replacing air filters, and cleaning fuel injectors.
  4. Plan Ahead: If you anticipate needing to run the generator for an extended period, such as during a planned power outage, make sure you have enough fuel on hand to last for the duration.
  5. Automated Fuel Delivery Systems: For larger generators or situations where the generator needs to run for extended periods, consider installing an automated fuel delivery system. These systems can monitor the fuel level in the generator and automatically order a refill when the fuel drops below a certain level.

Generator Cranks, But Won’t Start

A generator that cranks but won’t start can be quite frustrating. Several factors can cause this issue, including problems with fuel, spark, or air delivery, or a combination of these factors. Here’s why this might happen and what you can do about it:

Reasons for a Generator that Cranks but Won’t Start:

  1. Fuel Issues: If your generator doesn’t have enough fuel, or the fuel is old and degraded, the generator may crank but not start.
  2. Spark Plug Problems: If the spark plug is dirty, damaged, or worn out, it may not be able to ignite the fuel-air mixture in the cylinder, preventing the generator from starting.
  3. Air Filter Issues: If the air filter is clogged, it can prevent the necessary amount of air from reaching the combustion chamber, making it difficult for the generator to start.
  4. Carburetor Issues: Over time, fuel can leave behind residues in the carburetor, clogging it and preventing the correct mixture of fuel and air from forming.

Solutions for a Generator that Cranks but Won’t Start:

  1. Check Fuel Levels and Quality: Make sure there is enough fuel in the generator. If the fuel is old or degraded, replace it with fresh fuel.
  2. Inspect and Replace Spark Plug: Check the spark plug for signs of wear, damage, or fouling. If necessary, replace it.
  3. Clean or Replace Air Filter: Check the air filter. If it’s dirty or clogged, clean or replace it to ensure that enough air can reach the combustion chamber.
  4. Clean the Carburetor: If the generator has been sitting for a long time with fuel in the carburetor, you might need to clean it. In severe cases, the carburetor may need to be rebuilt or replaced.
  5. Check for Proper Oil Level: Some generators have a safety feature that prevents them from starting if the oil level is too low. Make sure the oil is at the correct level.


While generators can sometimes be finicky, understanding the common reasons they fail to start can help you troubleshoot and resolve the problem. Remember, regular maintenance is key to the reliable operation of your generator. When your power goes out, you want to be confident that your generator will start up and keep things running smoothly.



Rayan is an engineer, lives in a farmhouse. He has a passion for electronics and alternative energy. He loves to share his thoughts with other people. That is why he started the blog.

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