Generator Maintenance Guide : Checklists to Keep the Power Flowing

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Correct and regular maintenance of your generator will ensure it remains reliable and lasts as long as it should. How often you need to do this will depend on any number of factors. In this guide to generator maintenance we’re going to cover all the bases for the various types of generators, operating conditions, and usage patterns.

With the correct maintenance, you can expect your generator to last anywhere from 10 – 30 years, possibly more. It will depend a lot on how often your generator is used. It goes without saying, that a generator that is used regularly will require more frequent maintenance than one that is used occasionally. Regardless of how many hours your generator runs through the year, it will require annual, bi-annual, and regular interval maintenance and inspections.

Maintenance will differ according to the type of generator and the operating conditions. A standby generator, for example, will usually require a more comprehensive maintenance program. These generators often have liquid cooling systems and the transfer switch will also need to be checked regularly. Portable generators tend to be simpler. They are air-cooled and don’t use an automatic transfer switch. That’s if they use a transfer switch at all. Different fuel types also require different maintenance procedures. So we also need to consider whether your generator runs on gas, diesel, propane, or natural gas.

VIDEO | Walk-through Generator Maintenance

How do you use your generator, and how often? An off-grid home will usually rely quite heavily on a generator, even if the primary power generation is renewable energy, like solar panels. Portable generators may be used for anything from a 100-hours a year, to 60-hours a week or more. This will all have an effect on what maintenance is required, and how often. Climate also plays a role. Generator maintenance in a cold climate will have some differences to a generator used in hot, or humid conditions.

With these many considerations in mind, you will need to adapt your maintenance to your situation and the type of generator that you use. Your owner’s manual will stipulate basic maintenance intervals and usually offers some instruction as to what maintenance procedures should be performed and when. This will be stipulated by running hours or a specified time period – whichever comes first.

We mostly think of engine maintenance. This is generally timed in accordance to the need for oil changes, typically every 50 – 60 hours or 1-year. However, there is much more to generator maintenance than oil changes and engine checks. Alternator maintenance is often over-looked, which can affect the generator safety, reliability, and lifespan.

Because there is so much to cover, and not all maintenance requirements are the same, I’ll be providing some basic generator maintenance checklists. In some cases, a procedure may only be applicable to a certain type of generator, like a standby generator or a diesel generator. Though, most checks and maintenance operations are common to all generators.

Following the checklists, I’ll provide more detail and offer explanations, where needed. I’ll also discuss generator storage and fuel storage.

Table of Contents...

1 Monthly Generator Maintenance
2 Annual Generator Maintenance
- 2.1 Before Storing your Generator
3 Generator Maintenance Tips

Monthly Generator Maintenance

Regular inspections and checks should be conducted roughly every month. If the generator has run for an extended period, these checks should be conducted once the generator is shut down, even if it has been less than a month since your last inspection.

Check engine coolant level, this generally applies to water-cooled standby generators.
Check engine oil level.
Check battery, then start and run the generator for about 5-minutes.
- When the engine is running, check for waring lights or alarms that may indicate a system failure or fault.
- If you’re using an automatic transfer switch, check that this is functioning correctly
Check for fluid leaks.
For an enclosed standby generator, ensure that the enclosure is clean and check for rodents and other vermin that may damage pipes and wiring.
Do a general visual inspection to ensure that pipes and wiring have not been damaged.
For standby generators, check fuel level and that the unit is switched to “Auto” once all other checks have been completed.
Diesel generators have a water filter. It is important to check this regularly and drain the water if needed. In humid climates, or if the generator has been running for an extended time period, this is of even greater importance.
If the generator has not been used for a month or more, connect the battery to a charger until it is fully charged.

Always Check —

Before manually starting a portable generator:

Wipe the generator down to remove dust or any flammable debris. If you have an air compressor or blower (like a leaf blower), this will be the best method of cleaning the generator and removing debris.
Check fuel and oil level. Top up where needed.
Check that the air filter is clean and not obstructed.
Check air cooling system for the engine. Make sure this is free of any obstructions and that the engine has adequate airflow for cooling.
Do a basic visual inspection of the wiring and fuel pipes.
Check for fuel leaks.
Before starting the generator, make sure the main supply breaker is in the off position.
Check extension cords before connecting to the generator.
If you’re using a propane generator, ensure that the propane tank, hose, and regulator are in good condition. Check for gas leaks by opening the valve on the propane tank and smelling for leaks and feel along the pipe, regulator, and fittings. It is always colder around the area of a gas leak.

Annual Generator Maintenance

Always refer to your owner’s manual with regards to annual service requirements. You may have to do this more than once a year if your generator is used regularly. I recommend you perform the following maintenance tasks every 60-hours of run-time, on average. But, use your manufacturer’s recommendations as every every generator is different. These are general guidelines.

Thoroughly clean the generator.
Remove oil, dust and other debris. You may need a wire brush and degreaser. A high-power blower, air compressor, or pressure washer will do the best job. Read more about generator cleaning below to ensure that you do this safely.
Drain engine oil and replace.
Replace oil filter, air filter, and fuel filter. Some air filters don’t need replacing, only cleaning. Refer to your manual to check what is required.

► For Diesel Engines : Check fuel and recondition if needed. Drain water from the fuel tank. Alternatively, drain the fuel and discard the old diesel, replacing it with fresh fuel. Diesel fuel contamination can lead to long-term engine and injector damage.

Change spark plugs (gasoline, propane, and natural gas engines).
Check coolant levels for liquid cooled engines.
Top up with anti-freeze. The coolant system should be drained and flushed clean about every three-years.
Your carburetor will need occasional cleaning.
If the generator is running erratically, this may indicate that the carburetor needs to be cleaned. Avoid doing this too often, as corrosive chemicals in the carburetor cleaning fluid can harm seals and other carburetor components, if used too often.
Check the crankcase breather, as well as any belts.
Check all wiring harnesses, pipes, and clamps.
Conduct a visual inspection of the alternator. Check for heat damage. Check for loose or damaged components.
Once the engine service and all visual checks have been completed, start the engine and allow it to reach operating temperature.
Check that the generator is running smoothly and not overheating.
Check output voltage and frequency, using a multimeter.

Do a comprehensive load test. Start with a load of roughly 20 – 25%, then gradually increase the load to full rated power. With each subsequent load increase, conduct the following checks.

Check that throttle control (or engine governor) increases the RPM as load is increased.
Check the voltage as load increases. No more than 5% fluctuation as the load changes. Some, cheaper generators may show a brief increase or decrease in voltage that is more than 5% (sometimes up to 50%). This should be for less than a second. Excessive voltage fluctuation may indicate the need to replace the Automatic Voltage Regulator (AVR).

Switch the generator off and allow to stand for about 5-minutes and the check the engine oil level again. Standby generators that aren’t used too often, will usually require a fuel stabilizer to be added to the gas tank at least once a year.
Switch the generator off and allow to stand for about 5-minutes and the check the engine oil level again. Standby generators that aren’t used too often, will usually require a fuel stabilizer to be added to the gas tank at least once a year.

Before Storing your Generator

Portable generators will often be used only a few times a year and will, therefore, be stored for long periods. It’s important to that a generator is prepared for storage and stored correctly.

Drain fuel from the carburetor.

Modern fuels can degrade within a month though, it’s generally accepted that gas can be stored safely for about three months. Any fuel left in the carburetor for this long will evaporate, leaving a sticky residue which will inhibit the carburetor function. Some generators may have a drain valve, making it easy to remove the fuel. If this is not the case, close the fuel supply valve with the engine running. Allow the engine to run until it dies from fuel starvation. This means all the fuel in carburetor has been used and the carburetor is empty.

Note : If you’re using propane (in the case of a dual fuel generator), there is no need to drain the carburetor.

Drain the fuel from the tank or add a fuel stabilizer.
Disconnect the battery to prevent discharge.
Always store your generator in a dry area where it is safe from damage.
Store your generator in an upright position as to prevent fluid spills.

Generator Maintenance Tips

If some of the procedures mentioned in the generator maintenance checklists are unclear, this section of the article should help.

Oil Change

Changing engine oil is not too complicated. It’s still a good idea to do things properly and observe some basic rules.

Always make sure the engine has cooled sufficiently before removing the oil drain plug to prevent burn injuries. Drain the oil into a large enough container so that the oil does not spill when carried. A flat open container that is wide enough to capture the oil without spillage is important. Replace the oil filter before adding new oil.

Use a wide funnel when pouring oil into the filler. Pour slowly as the funnel can easily overflow and spill oil onto the engine. Always fill engine oil to the correct marking on the dipstick. Overfilling or under-filling the oil sump is equally dangerous. As you reach the lower marking on the dipstick, add oil in small increments. Check the level before adding more oil. Wait a few seconds before checking the oil level, as it takes time for the oil to trickle through to the sump.

When fitting the oil filter, ensure that the rubber seal at the base of the filter contains no dust and is firmly seated. Applying a thin film of oil to the seal will help. Tighten the filter only to the point where it seals properly. Over-tightening the oil filter can cause damage and will make it difficult to remove later. You can always check for leaks and tighten the filter slightly once new oil has been added. The same applies to the drain plug, do not over tighten. Ensure that the thread is aligned correctly to prevent cross-threading. If the oil drain plug is not forming a good seal, don’t try tightening beyond a reasonable torque. You can use a fiber or copper washer to help seal the plug. Otherwise replace the plug.

It is important to dispose of used oil correctly. Old engine oil is an extreme environmental hazard. You should take all used engine oil to an approved oil recycling center.

Changing Spark plugs

Replacing spark plugs is also a fairly simple procedure, as long as you do it correctly.

Spark plugs require the exact gap between the electrodes. This is the bent metal plate at the base of the spark plug and the carbon rod protruding from the ceramic housing. The spark plug gap is set at the factory. However, this may not always be correct by the time you use the plug. Check the gap with a gauge and adjust if necessary. If you can’t find the correct spark plug gap setting, this information is widely available on the internet, as well as instruction videos on how to set the gap.

Always align the thread carefully before tightening a spark plug. You should also take care not to damage or crack the ceramic housing. This happens easier than you may think. If the ceramic housing is damaged, do not use that spark-plug.

If the spark-plug is not sufficiently tightened, the engine will lose compression and run badly or not at all. If the plug is over tightened, you may damage it or the engine housing. You should find a torque setting on the spark-plug packaging. If you have had little experience installing a spark plug, use a torque wrench, set to the manufacturer specifications.

When replacing the spark-plug wire, ensure that that the boot fits snugly over the top of the plug. You should feel resistance when pulling back as if to remove the wire.

How to Clean your Generator

Cleaning the generator, carburetor, or air filter, all needs some careful consideration.

It’s important to keep a generator clean, both as a safety precaution and to ensure it operates properly. Flammable debris, like wood chips, sawdust, or dried leaves can combust when the generator gets hot. This is a common issue with generators that are stored in a garage, especially if the garage is also used as a home shop. So a generator should be cleaned regularly, even when not used. Some dirt may become ingrained and be difficult to remove if left for too long.

Compressed air is one of the best ways of removing loose debris from a generator. To remove spilled oil and gas, a detergent will be required. If you use a pressure washer with water and detergent to clean your generator, be aware of the dangers that residual moisture can present. After cleaning a generator with water, it’s best to use pressurized air or a blower to dry it and displace any water. Alternatively, you can leave the generator in the sun until dry. Always make sure the generator is completely dry before starting.

When cleaning your generator, check for rust on the frame, engine, and alternator. Rust should be dealt with in a timely manner, as it only gets worse over time. Sand a rusted area and clean. Make sure no dust is left behind. Then apply paint or rust inhibitor to the affected area.

Occasionally the carburetor needs cleaning. This is only necessary if you notice that the generator isn’t starting easily or does not run smoothly. The easiest way to do this, is to use a can of carburetor cleaner. You spray the liquid into the carburetor and around the outside. It will probably be difficult to start the engine immediately after spraying the liquid. Once you get the engine started, pull hard on the throttle a few times until the engine idles smoothly.

Most air filters can be cleaned. This can be done using warm soapy water and allowing the filter to dry before installing. You can also blow the filter clean with pressurized air.

Battery Maintenance

The battery is another area of generator maintenance that is often ignored. Most batteries don’t last as long as they should, simply because of poor maintenance.

Generally, the lead acid batteries that we buy today are mostly maintenance-free. This means that there is no need to top up distilled water or battery acid over the lifetime of the battery. But this does not mean the battery is entirely maintenance-free, it’s just easier. Battery degradation happens mostly because of poor cycling. This means that a battery should always cycle between a state of full charge to no more than 80% of it’s rated capacity.

When a lead acid (or calcium) battery stands for long periods, it gradually discharges. If a battery is left in a state of low charge, the lead plates inside the battery corrode rapidly. High temperature (above 77°F) also promotes corrosion. Though temperature is most relevant when the battery is charging or discharging.

It often happens that a generator will stand unused for longer periods of time. It is, therefore, important to conduct periodic battery maintenance during this time. I’ve already mentioned that a battery should be disconnected when the generator is stored. This reduces the current discharge while the generator is not in use. It is just as important to charge the battery frequently. Every month is ideal, but at least every three months.

There are several precautions that need to be observed when charging a lead acid battery. The first is general safety. Always charge the battery in a well ventilated area as acid fumes may be released during the charge cycle. Charge the battery in a cool environment (77°F or less). Use a good battery charger and select the correct charge amperage.

Overcharging, or charging a battery too rapidly is a major cause of deterioration. In fact, the lowest amp setting will always be best. Smaller batteries (40AH or less) usually charge best at 10A. As the battery size increases, the amperage can be higher. This can be as high as 20A for batteries 100AH or more. Since a generator battery is usually small, it’s best to use the lowest amp setting (5 or 10A). The battery will always charge to full, regardless of the charger amps. It just takes longer at a low amperage. Rapid chargers are the worst thing for a lead acid battery. This should only be used in an emergency, like when you need to start a car with a weak battery urgently.

Remove the battery from the charger as soon as it is fully charged. Even though most reputable battery chargers are protected against overcharging, they are not perfect. There will always be a small degree of unnecessary overcharging and heat is produced which is not good for the battery. Once a year, a battery should undergo a maintenance cycle. This involves gradually discharging the battery until completely discharged, then recharging it full immediately after. This process reenergizes the electrolytes. The best battery chargers have a maintenance cycle option and automatically discharge and charge the battery under optimum conditions

Storing Fuel

There are basically three types of generator fuel that may need to be stored: gasoline, diesel, and propane. Since natural gas standby generators are supplied by a pipeline connected to a bulk supply, there is no need to be concerned about fuel storage for these generators.

Gas Storage

Gas evaporates very quickly and vaporizes at a relatively low temperature (140-degrees). This means that it evaporates easily at normal room temperature. The evaporated fumes are extremely volatile and can be a serious fire hazard. Furthermore, as gas evaporates, heavier components remain, causing a residue that is harmful to your carburetor and, possibly, the engine. To increase octane levels, modern fuels use additives. While ethanol based fuels evaporate slower, other additives cause a more rapid deterioration. The end result is that modern fuels cannot be stored as long as in the past.

Given the volatile nature of gas, it is important to store it in a container designed for this purpose. Gas cans have pressure relief valves, usually in the filler cap. This allows the evaporated gas fumes to be released at a controlled rate. Minimizing loss, whilst not allowing the pressure inside the gas can to reach dangerous levels. Storing gas at a low temperature is also preferable as this reduces evaporation.

Even under perfect storage conditions, gas will evaporate and deteriorate. In the past, it was said that gas could be stored for 3 – 6 months without deteriorating. With modern fuel additives, this has now changed. Today, we can only store gas for 1 – 3 months without it deteriorating. Since we never know how long the gas was stored before we bought it, it’s probably better to steer on the side of caution when deciding how long it is going to be stored.

If you intend storing gas for longer than a month, add a fuel stabilizer. This prevents gas deterioration for up to a year, if you use a high-quality fuel stabilizer. It should go without saying, gas is extremely flammable, and this should be considered when storing. Keep away from direct flames or intense heat sources, like a space heater. Always store gas far from any flammable materials or chemicals.

Diesel Storage

Diesel does not evaporate easily and is, therefore, not as volatile as gas. It takes a high temperature or pressure, before diesel combusts. This makes it easier to safely store diesel.

Despite this, diesel has its own complications, it is extremely susceptible to contaminants. Water and particles found in the air can result in serious damage to the diesel fuel system and injectors. In some cases, diesel contamination may damage your engine. Under normal use, the water and diesel filters fitted to the generator will prevent these contaminants from causing unwanted damage.

Long-term diesel storage will cause a high concentration of contaminants that cannot be filtered by normal means. Depending on environmental conditions, like humidity and contaminants in the air, this can be anything from three months to a year. The only sure way to check for diesel contaminants is to have it tested. If high contamination levels are found, it will be necessary to recondition the diesel. This is an advanced filtration process. Testing and reconditioning diesel can be costly and, perhaps, not worth the expenditure for a small amount of fuel.

Some people may choose to dump unwanted contaminated diesel if testing and reconditioning proves to be too costly. Though you should be aware of the environmental hazards and get advice from local authorities as to where you can safely dispose of unwanted diesel. It might be better to use the old diesel for other purposes, like as an accelerant for starting fires, or preserving outdoor woodwork.

Propane Storage

Even though propane evaporates at a much lower temperature than gas, making it more volatile, it is safer and easier to store. This is due to the nature of a propane storage tank.

The high-pressure tank used for propane storage totally eliminates fuel loss through evaporation and fuel deterioration. This means that you can store propane for long periods, almost indefinitely, and there’s a lower fire risk.

This does not mean that storing propane is entirely risk-free. An important consideration is the condition of your propane tank. Since it is the tank, and not the fuel, that makes propane safer to store, the tank should be checked regularly. Propane suppliers need to ensure that the tank is fit for use and when it will be no longer be viable for safe usage. Sometimes the tank needs to be replaced, other times it may need refurbishing of seals and other components. The only way to be sure is to have your propane tanks professionally checked each time they are refilled.

Propane tanks also need to be stored away from any fire hazard, like high-temperature appliances or open flames. They should be stored a safe distance from flammable materials and chemicals. Always ensure that the valve on the tank is securely closed before storing. A cool storage environment is preferable.