Diesel generators: How to maintain a diesel generator

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In this article, we look at the 10 best practices to maintain a diesel generator.

Diesel generators are considered the most durable, reliable and sturdy. In addition, they are said to be the cheapest to operate due to the low fuel costs compared to the other types of generators that run on fuels such as gasoline and propane.

The 10 essential steps discussed herein will go a long way to ensure that you get the most out of your diesel generator.

1. General inspection of your diesel generator 

During the running of the diesel generator, the exhaust system, fuel system, DC electrical system and engine require close monitoring for any leaks that can cause hazardous occurrences.

As with any internal combustion engine, proper maintenance is essential. According to Georgia Scott, standard servicing and oil change times are recommended at 500 hours. Scott works with Constant Power Solutions one of the leading Generator and Power Equipment Manufacturers in the UK. However, he says, some applications may require shorter servicing times which is why after-sales services should be top-notch.

For a better diesel generator, inspect if possible every two weeks or once a month at minimum. The alternator, controllers, AVR, and entire sensor system also need regular checkups as well as wiring harnesses for integrity. Deep diagnostics will allow the generator to run freely and easily and ensure that it is available the moment you need it.

servicing a generator

2. Diesel generator lubrication

Doing regular inspections of your diesel generator lubrication is also one of the best practices for maintaining a diesel generator.

The engine oil must be checked while shutting down the generator at regular intervals using a dipstick. Allow the oil in the upper portions of the engine to drain back into the crankcase and follow the engine manufacturer’s recommendations for API oil classification and oil viscosity. Keep the oil level as near as possible to the full mark on the dipstick by adding the same quality and brand of oil.

servicing a generator

The oil and filter must also be changed at acclaimed time intervals. Check with the engine manufacturer for procedures for draining the oil and replacing the oil filter and their disposal is to be done appropriately to avoid environmental damage or liability.

Nevertheless, it pays to use the most dependable, highest-quality oils, lubricants and coolants to keep your engine working. Therefore, according to Jim Girard of Lubriplate from Newark NJ, in the US, it is highly advisable to purchase lubricants that comply with the Original Equipment Manufacturer’s (OEM) generic lubricant specifications.

3. Check your diesel generator cooling system

Check the coolant level during shutdown periods at the specified interval. Remove the radiator cap after allowing the engine to cool, and, if necessary, add coolant until the level is about 3/4 in. Also, remember to check on coolant filters and change when necessary.

Heavy-duty diesel engines require a balanced coolant mixture of water, antifreeze, and coolant additives. Inspect the exterior of the radiator for obstructions, and remove all dirt or foreign material with a soft brush or cloth with caution to avoid damaging the fins.

Radiator flushing is also a critical diesel generator maintenance practice to avoid overheating or high temperatures on the engine. If available, use low-pressure compressed air or a stream of water in the opposite direction of normal air flow to clean the radiator.

4. Check your diesel generator fuel system 

Diesel is subject to contamination and corrosion within a period of one year. Therefore regular generator set exercise is highly recommended to use up stored fuel before it degrades. The fuel filters should be drained at the designated intervals due to the water vapour that accumulates and condenses in the fuel tank.

Regular testing and fuel polishing may be required if the fuel is not used and replaced in three to six months. Preventive maintenance should include a regular general inspection that includes checking the coolant level, oil level, fuel system, and starting system. The charge-air cooler piping and hoses should be inspected regularly for leaks, holes, cracks, dirt and debris that may be blocking the fins or loose connections.

Diesel generator extended fuel maintenance intervals

Some engines used in Stand-by generating set applications have had a few issues concerning diesel fuel. This is according to the Marketing Department of the Italy-based Visa SpA, one of the world’s leading gensets suppliers, dedicated to the design, production, sales and rental of generating sets.

“While the engine maintains its mechanical properties, it can give rise to problems related to the quality of diesel fuel. The chemical makeup of diesel fuel has changed in recent years. A certain percentage of biodiesel at low or high temperatures releases impurities, while a certain percentage of biodiesel at warm temperatures mixed with water (condensation) can be the cradle of bacterial proliferation.

Besides, the reduction of Sulphur reduces lubrication, which eventually blocks the fuel-injection pumps.”

servicing a generator

“Moreover, by purchasing a genset,  it is important to know that a wide range of optional accessories is available that allow extended maintenance intervals and ensure providing quality power throughout the genset’s life. In the mobile range, for example, Visa SpA offers fuel water separator filters, giving the customers the reassurance required when engine failure is not an option, or the fuel tank inspection points.”

Ms. Clarizza Cortez of Adpower one of the leading providers of Diesel and Gas Generators in the Middle East and North Africa also mentions that, since the fuel quality is bad in most countries, they install Water Separator Fuel Filters and additional filtration systems to protect the sensitive fuel injection system; and advise the customers to replace the elements on time to avoid such breakdowns.

5. Check your diesel generator batteries 

Weak or undercharged starting batteries are a common cause of standby power system failures. The battery of your diesel generator must be kept fully charged as well as well-maintained, regularly tested and inspected.

The latter helps to know the status of the battery and avoid any start-up hitches of the diesel generator. Furthermore, they must be cleaned, and the specific gravity and electrolyte levels of the battery checked frequently.

• Testing batteries

Merely checking the output voltage of your diesel generator batteries is not indicative of their ability to deliver adequate starting power. As batteries age, their internal resistance to current flow goes up, and the only accurate measure of terminal voltage must be done under load. On some generators, this indicative test is performed automatically each time the generator is started. On other generator sets, use a manual battery load tester to attest the condition of each starting battery.

• Cleaning batteries

Keep the batteries clean by wiping them with a damp cloth whenever dirt appears excessive. If corrosion is present around the terminals, remove the battery cables and wash the terminals with a solution of baking soda and water (¼ lb baking soda to 1 quart of water). Be careful to prevent the solution from entering the battery cells, and flush the batteries with clean water when finished. After replacing the connections, coat the terminals with a light application of petroleum jelly.

• Checking specific gravity

In open-cell lead-acid batteries, use a battery hydrometer to check the specific gravity of the electrolyte in each battery cell. A fully charged battery will have a specific gravity of 1.260. Charge the battery if the specific gravity reading is below 1.215.

• Checking electrolyte level

In open-cell lead-acid batteries, verify the level of the electrolyte at least every 200 hr of operation. If low, fill the battery cells to the bottom of the filler neck with distilled water. Always disconnect generator batteries when not in use.

6. Routine diesel generator maintenance exercise

Regular exercising keeps the engine parts lubricated and thwarts oxidation of electrical contacts, uses up the fuel before it deteriorates, and helps to provide reliable engine starting. Engine exercise is recommended to be executed at least once a month for a minimum of 30 min. loaded to no less than one-third of the nameplate rating.

Most importantly, when it comes to engine maintenance, according to Peter Whitfield of YorPower a leading independent UK diesel generator manufacturer, it is recommended to do inspections regularly because preventative maintenance is better than reactive maintenance. Nevertheless, it is of utmost importance to follow the designated service procedure and intervals.

servicing a generator

7. Clean your diesel generator 

Oil drips and other issues are easy to spot and take care of when the engine is nice and clean. Visual inspection can guarantee that hoses and belts are in good condition. Frequent checks can keep wasps and other nuisances from nesting in your equipment.

The more a generator is used and relied on, the more it needs to be taken care of. However, a generator set that is rarely used might not need a lot of care.

8. Inspect your diesel generator exhaust system 

In case there are leaks along the exhaust line which usually occurs at the connection points, the welds and the gaskets; they should be repaired immediately by a qualified technician. Make sure all intake and exhaust ports are well covered.

Nevertheless according to Ms. Arlene of Maverick Generators in South Africa, always make sure your units are serviced. Especially 24 hours before using your generators. “For standby generators for example you need to have your units serviced 150hrs on average. However, if the generator is used constantly the hours go up much quicker and in more regular intervals,” she adds.

Furthermore, according to Ryan Mason of Lister Petter a manufacturer of internal combustion engines from the UK, it is quite advantageous when you have maintenance kits for different service intervals.

9. Service your diesel generator air cleaner

servicing a generator

The air cleaner should be serviced after every 500 hours of engine operation with a filter element made of special highly porous cardboard or, if compulsory, by the use of the clogging signalizer. Servicing the air cleaner comprises purging of the main filter constituent, which holds dust coming into the air cleaner.

The control filter element clogs states for damage to the main filter parts (paper curtain broken, bottoms coming off). In such a case, it is required to purge the control filter element and put back the main one. Also, inspect the fresh air inlet and hot air discharge windows or ducts to make sure they are not closed or blocked.

10. Wash your diesel generator engine breathers

The last of the best practices to maintain a diesel generator in our list is washing the engine breathers. The engine breathers should be cleaned with diesel fuel after every 2,000 engine operation hours.

The diesel generator maintenance on breathers is done by removing the housings, taking the breathers from the cylinder head cover caps, and washing and purging them with compressed air. The breathers and their housings should then be put back in place.

41 thoughts on “Diesel generators: How to maintain a diesel generator”

  1. We are well known generator suppliers in UAE. As the Best Diesel Generator Suppliers In UAE, we offer genuine diesel generators powered by world class engines in Dubai & Sharjah.

  2. Thanks very much, I learn a lot from this so I will be able to finish my internship report

  3. the best maintenance is to inspect, and operate under load every two weeks if possible, once a month at minimum. Have maintained a standby generator for 8 years in this manner. Just last month the generator failed to start. The circuit that automatically charges the battery
    had faulted and the battery had discharged. Jumped battery and recharged and corrected ground fault. Would not have detected problem without timely exercise of system. Keep wasp sticky trap in enclosure at all times as we have mud daubers as frequent invaders. Never a problem with trap. Very few spiders as I think they feed on wasps and other insects.

  4. Maintenance is important after the installation of any type of generator. This is to ensure that the engines are functioning very well. For maintenance, it’s highly recommended to hire a pro than DIY.

  5. With proper maintenance and installation, generators become reliable and helpful to you and to your home, providing backup power to avoid stress.

  6. Thanks for the info. I noticed that you forgot radiator flushing which is critical in
    avoiding overheating or high tenp on engine

  7. Thanks for informing me that we should probably do regular testing and fuel polishing for our diesel-powered generator if the fuel is not used or replaced in three to six months. My husband and I plan to spend the holiday season in our vacation cabin. Since we haven’t been back to the place for about a year now, we’ll check the generator and do some maintenance before using it again. Hopefully, there’s a diesel depot nearby that can supply us with fresh diesel.

  8. Thank you thia is really helpfull. And i am looking for smart disel generator service and maintenance course on line. Detail. Please advice

  9. Thanks for explaining that the fuel should be used and replaced in six months to avoid issues. My brother is looking into getting a diesel generator to use in his industrial manufacturing plant by the freeway in the next city over. I’ll pass along this info so he can plan an effective timeline for working with a diesel fuel delivery service!

  10. Thank you so much for the information, good tips ,worthy advise and so much benefit in this article. Now I can do the maintenance and repairs myself thanks once again

  11. Thanks for your useful tips. I was really worried about the maintenance of the diesel generator purchased recently for my textile showroom. The above step by step maintenance tips will help to take the best care of my diesel generator.

  12. I am busy to learn more about the generator .6000 take about 24A and is small generator
    500kva supply the big building like hospital.jail

  13. Amazing Write-up, Now I’m understanding Clearly how we maintain the generators properly

  14. Amazing write-up, This post understand clearly how we maintaining generators.

    We also follow some common factors for maintaining the generators regularly,

    – Disconnect generator batteries.
    – Drain fuel system and change fuel filters.
    – Drain coolant and change coolant filters.
    – Replace air filters.
    – Ensure all intake and exhaust ports are covered.
    – Disconnect all generator supply connections.

  15. I appreciate that you mentioned that it’s important to keep your generator clean. I think it would also be smart to know a good repair company that could help you if something happened. Thanks for the tips for generator maintenance.


  17. Thanks for sharing a great post about the proper maintenance of a generator,Please give me
    Maintenance schedule of Generator, checklist and its Maintenance Plan

  18. Please my 500kva generator stops running after 30mins after cooling it will start again but after another 30mins or 45mins it will stop again. What is the solution what can I do?

  19. Really well written and informational guide about diesel generator maintenance. Most of the people sell their generator because they don’t take proper care of their generators as suggested in this article.

    These are really important key steps for proper diesel generator maintenance. We usually take care of these steps for Good maintenance and proper diesel generator working.

    Finally, it’s a must follow article for any individuals who own diesel generator for their power need in an emergency.

  20. This post is insightful. I really learn a lot from it. Please can you talk more about troubleshooting of a genset?

  21. One thing to keep in mind when servicing an industrial-sized generator is the need to make sure that maintenance is conducted on it just to make sure it’s working on. Conducting maintenance on the machine is important since you would want to make sure that it’s working at the critical time you would need it to work. If I had the chance to own one of the bigger generators then I would also want to make sure it would be available in case of emergencies.

  22. Please give me
    Maintenance schedule of Generator, checklist and its Maintenance Plan

  23. You are missing some elements of equal, in not more importance. The alternator, AVR, controllers, and entire sensor system to manage the generator, wants regular check ups. Multi-phase generators need to kept in sync not only for phasing, but also for frequency and voltage. This system controls engine speed, and when phasing or frequency is off the control systems will ask the engine to work harder. This decreases engine life, and increases fuel consumption. It’s a aggregate of systems that need to talk back and forth to ensure optimum generator performance. Sensors need to be tested, wiring harnesses to be be checked for integrity, and all fuel/air delivery, and cooling subsystems need to be checked thoroughly by competent technicians. Deep diagnostics will ensure the unit runs freely and easily and ensure the unit is available when you need it.

  24. Thanks for sharing a great post about the proper maintenance of a generator, For my Home Generator Repair I hire a only professional team of Home Generator repair.

  25. Thanks for explaining how it’s important to check the engine oil of the diesel generator on a regular basis in order to figure out whether you need to add or change it. When doing this, it might help to visit a diesel depot or another auto shop that specializes in these services. This could ensure that it’s handled by an experienced professional who knows the best methods and equipment to use to keep everything in the best condition.

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