All Generac XT8500EFI Problems, Reasons, Solutions!

Generac’s XT8500EFI portable generator is ideal for backup power during power outages or as a source of power in remote areas. It is also very popular worldwide because of its amazing features. 

However, like any other machine, your Generac xt8500efi also goes through some problems. 

So, what are the Generac xt8500efi problems

Generac xt8500efi encounters engine starting issues and obstacles during operation. The AC output does not come out even though the engine is functioning. The battery is known to deplete too fast. Moreover, the faulty indicator light may remain lit up even after you turn off the key. Every issue requires a particular solution. 

You won’t be able to solve the problem by just knowing the problems. You can find the exact solutions to each problem in this article. 

Generac xt8500efi Problems: Reasons and Solutions!

Despite all the good things about this device, it has a few drawbacks as well like any other electric device. Let’s get to know the common problems people suffer with a lot.  

Problems Reasons Solutions 

Engine won’t start
Weak battery Dirty air filterFuel issuesCharge the battery Clean the filter Change fuel

Engine is running but ac output is not available
Circuit breaker OPEN Poor connection or defective cord set Reset the breakerTighten or change the cord set 

Engine shuts down during operation 
Low fuelFault in engineLow oil levelTop up the tank Inspect and address the issueFill crankcase correctly
Engine lacks in power High loadClogged spark arrestor Decrease the load Clean and replace 
Battery deplete too fast Inappropriate charger Overcharged battery Choose the perfect charger Don’t overcharge 
Fault indicator light staying litFaulty indicator light Wiring issuesReplace Replace 

Problem 1: Engine Won’t Start 

Sometimes the users of Generac xt8500efi experience that the engine isn’t starting at all. If the engine won’t start, there are several reasons that can be responsible. You should check one by one to diagnose the issue.

Engine Won’t Start

Reason 1: Weak Battery

The first and foremost reason the engine does not start is having a weak battery. Leaving your generator’s battery on a half charge for more than 6 months will prevent it from starting.


You must ensure that the starter battery is fully charged and capable of providing enough power. If the battery is low on charge or is not functioning properly, it may be preventing the engine from starting.

Also, make sure the battery terminals and high-current wires to the starter solenoid and frame ground are secure.

Reason 2: Dirty Air Filter

If the air filter is dirty or clogged, the engine of Generac xt8500efi won’t be able to start. A dirty air filter restricts the flow of air to the engine, which is essential for combustion. 

A dirty air filter can also cause the engine to run too lean (too much air, not enough fuel), which can also lead to starting issues.


Check the air filter and clean them if you find it is clogged. You can clean the Generac xt8500efi air filter just by following the steps below. 

  • First of all, turn off the generator and let it cool down. Then bring the generator to a well-vented place. 
  • Now, find the air filter which is located in the plastic air filter housing box. Then, bring out the filter by unclipping the front panel of the housing.
  • At this point, blow off the dirt or you can use a vacuum cleaner to clean the dirt. Then, wash the filter with a mild washing agent. Put it in the sun to dry.
  • After the filter gets dried out properly, lubricate the inside with motor oil of the filter that would be facing the housing. Then place the filter again where it was. 

If any of them is not responsible for not starting your engine, top up the oil level and ensure the fuel you’re using is of good quality. Also, the spark plug should be changed if they’re bad.

Reason 3: Fuel Issues

Any contamination adjoint to fuel will result in the engine failing to start. This includes the fuel becoming stale, the presence of water, or just simply a low fuel level. Stale fuel can corrode your Generac xt8500efi’s fuel system. 

Also, contaminated fuel clogs up the generator’s pistons and carburetor, preventing it from starting. Stale fuel has a darker or muddier appearance with a different odor, not typical of normal fuel


At first, you need to drain the stale gas from your generator. Then, place a funnel in the fuel tank hole. Pour in fuel up until the tank is ¾ full. Then put the tank cap back in its place and tighten it with your hand. Now, your generator will be back in business! 

Problem 2: The Engine is Running But AC Output is Not Available

This is the next potential problem the users of Generac xt8500efi face. There are several possible reasons why your generator engine is running but the AC output is not available. You can troubleshoot the issue by checking these things. 

Reason 1: Circuit Breaker OPEN

When a circuit breaker is “OPEN” it means that the breaker has tripped or been manually turned off, and the circuit is no longer receiving power. 

An open circuit breaker interrupts the flow of electricity to a specific electrical circuit or piece of equipment, preventing it from operating. 


Ensure the generator’s circuit breaker isn’t tripped. Reset the circuit breaker if it tripped. To reset an open circuit breaker, you need to first identify the reason for the tripping and resolve the issue. 

Once the issue is resolved, you can then reset the circuit breaker by switching it back to the “ON” position.

Reason 2: Poor Connection or Defective Cord Set

Poor connections or a defective cord set can result in a low voltage or intermittent power supply to the engine, which can prevent it from starting. Also, poor connections in the cord set can cause the ignition system to fail, preventing the engine from starting. 


To get over the situation, you should check the connections and cord set. Follow the steps below-

  • First, look for loose connections. Use a wrench or pliers to tighten any loose connections. Ensure the connections are snug, but not over-tightened.
  • Then, if you find any frayed or broken wires, you will need to repair or replace them. If the cord set itself is defective, you may need to replace it entirely. 

If you don’t have enough technical knowledge, you should go for professional help. 

Problem 3: Engine Shuts Down During Operation

Generac xt8500efi’s engine often shuts down while it’s running. If an engine shuts down during operation, it means that the engine has stopped running unexpectedly while in use. This can happen for a variety of reasons. Let’s get to know them.  

Reason 1: Low fuel

Fuel issues are one of the most common causes of engine shutdowns during operation. This can include problems like not having fuel at all or enough fuel. Low fuel is also a major reason for your Predator generator’s electric start not working.


Check the fuel indicator gauge properly. If you find the oil level marker is low, add enough gas to the fuel tank.  

Reason 2: Fault in the Engine

If the engine itself has faults that can also cause an engine to shut down during operation. If the battery alternator or wiring is going with issues, the engine won’t function. An engine can shut down unexpectedly if a belt breaks or a component seizes.


Finding any fault in the engine is a tricky job to do. So, it’s time to identify the cause of the issue and take appropriate action to address it. 

Depending on the cause, this may involve repairing or replacing components. Nevertheless, it’s better that you’re taking professional help. 

Reason 3: Low Oil Level

Engine oil is essential for your generator. It lubricates the moving parts and prevents the engine from seizure. You need to check the oil level every time before starting the engine.


Place the unit on a level surface. Make sure it’s turned off and the spark plugs disconnected. Now simply follow the steps below.

  • Clean the area around the oil fill and remove the dipstick adjoint to it. 
  • Wipe the stick clean and push it into the filler neck.
  • Bring out the dipstick and verify oil level is within the safe range ( H to L). 
  • If it’s closer to the L mark, slowly pour oil into the oil fill opening using a funnel. Avoid overfilling.
  • Replace the dipstick back in its place.

Generac officially recommends using petroleum-based oil (Synthetic 5W-30) for smooth operation and good health of your engine.

Sometimes, you will find the generator starting and shutting off right away. Your precious xt8500efi is equipped with an Automatic COsense shut-off sensor. 

If you try running the generator in the garage with exhaust, it will get triggered. Always keep it in an outside open area, far from windows, doors, and vents.

Problem 4: Engine Lacks in Power

The Generac xt8500efi engine sometimes does not provide enough power. Power deficiency indicates that an engine isn’t performing as well as it should and isn’t producing as much power as it should. Let’s find out the factors responsible for this. 

Reason 1: The Load Is Too High 

A high load on an engine can result in a lack of power. This is because the engine is required to produce more power than it is capable of, which leads to potential damage to the engine. 

High loads can result in increased wear and tear on engine components, which results in a reduced engine lifespan.


The solution is pretty obvious. You have to reduce the load which will help to increase the efficiency of the engine. Knowing the generator’s size for different hp air compressors will aid you in this section. 

Reason 2: Clogged Spark Arrestor

The next potential reason is having a clogged spark arrestor. A clogged spark arrestor can cause an engine to lack power by restricting the flow of exhaust gases out of the engine. 

So, clogged spark arrestors can create back pressure in the exhaust system, making the engine work harder to expel exhaust gasses.

Clogged Spark Arrestor

Read also: Can You Use A Jump Starter While Plugged In?


When a spark arrestor is clogged, you should remove it from the exhaust system and clean it thoroughly. A wire brush or other appropriate cleaning tool can usually be used for this cleaning task. 

Remember if the spark arrestor is damaged or excessively clogged, it may need to be replaced.

Problem 4: Battery Deplete too Fast 

A Generac xt8500efi user will often experience battery depletion even after charging properly. Battery depletion refers to the process by which a battery gradually loses its charge over time as it is used to power a device.  

As a battery powers a device, the chemical reactions that generate the electricity inside the battery gradually consume the chemicals inside it, leading to a gradual reduction in the amount of energy that the battery can store and deliver. 

There could be several reasons why the battery in a Generac xt8500efi generator may deplete too quickly. 

Reason 1: Inappropriate Charger 

The charger in the generator may not be functioning properly, leading to inadequate charging of the battery. Or the charger may not be proper for the battery. 

In fact, it doesn’t matter how much you charge your battery if the charger is not appropriate to ensure enough charge.

Inappropriate Charger


The probable solution to this problem is having a trickle charger which should be installed all the time. Also, if you’re using a battery from the brand “Battery Tender”, you should allow it to hook up all the time. 

Reason 2: Battery Is Being Overcharged 

The next potential reason could be you’re charging the battery too much. When a battery is overcharged, it can lead to a buildup of gas inside the battery. It causes the battery’s electrolyte to break down, leading to a loss of capacity and an overall reduction in the battery’s lifespan. 


To get over the issue, adjust the charging rate (amps) at full charge (around 13-14 V for a 12 V lead-acid battery). Also,  ensure that you regularly inspect and maintain your generator’s charging system to prevent the battery from being overcharged. 

Problem 5: Fault Indicator Light Staying Lit

You may notice that the fault indicator light of Generac xt8500efi remains lit even after the turnkey is taken from OFF to RUN If the problem persists even after changing the battery, it indicates some other possible reasons.  

Reason 1: Faulty Indicator light 

An indicator light that is faulty is the first possible cause. If the light is faulty, it may stay on even after you turn it off. 


If you find the indicator light is faulty, you have to replace the light.

Reason 2: Wiring Issues 

Then, faulty wiring or a short circuit can cause the indicator light to stay on, even when it’s supposed to be off. 


Check the wiring and connections for any signs of damage or loose connections. If you find the connections are loose, make sure to tighten them properly. On the other hand, if you find any sign of damage, you must replace the damaged wiring. 

Fault Indicator Codes

Fault Indicator Light is responsible for showing error codes related to problems with your generator (e.g. P0123, P0118, etc). 

Check the official manual of xt8500efi (page 20) for their proper reasons. You should always consult a technician for troubleshooting problems regarding these codes.

Frequently Asked Questions (FAQs):

What is the lifespan of a Generac generator?

The lifespan of a Generac generator is around 25 to 30 years. However, it can vary depending on various factors, such as usage, maintenance, and the specific model. A generator’s lifespan can also be affected by the conditions under which it operates. Extreme temperatures, humidity, and exposure to harsh elements can cause wear and tear.

Why do Generac generators fail?

A lack of proper maintenance is responsible for Generac generators’ failure. It can lead to physical damage. Overloading the generator can cause it to fail, and it’s essential to use the generator only for its intended purpose and within its capacity limits. Apart from that, a lack of proper usage can lead to failure. 

How do I clean my Generac error code?

To clean a Generac error code, you must first identify the specific error code being displayed. Turn off the generator and reset the circuit breaker. Then you need to turn it back on. If the problem has been resolved, the error code should be cleared.

Read also: What Size Generator to Run Different HP Air Compressors


Hopefully, you’ve found out the Generac xt8500efi problems which you can experience in the generator’s lifetime. Some problems are very easy to get over, which you can do just by following the article. Others may need professional assistance. So, don’t hesitate to go with the professional mechanic if it demands.

 Also, don’t forget to take proper care because it can decrease the number of issues. You have a great venture ahead of you.

Also read: 11 Reasons Predator Generator Electric Start Not Working

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About Frank Diaz

Hi everyone, my name is Frank Diaz and I am the face behind GaragestPicks. I studied Mechanical Engineering at Georgia Institute of Technology and worked as a mechanic for over 20 years. I love working on cars and doing DIY projects around the house. I write this blog to share my knowledge and help others fix their cars with most common tools.

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