Regular, comprehensive servicing is crucial for both the performance and lifespan of your diesel generator. It ensures that every component is in full working order, so that the generator is ready to activate and provide backup power in an emergency.
Unfortunately, servicing is sometimes neglected, or too long passes between engineer visits. This could put your equipment – and your site, business and people – at risk.
This is why it’s essential to have a service schedule in place which suits the needs of your business and the specifics of your site.
How Often Should A Diesel Generator Be Serviced?
Ideally, a diesel generator should be professionally serviced every 6 to 12 months, or after 250 to 500 running hours (whichever comes first).
Annual servicing is common for standby generators, but this may not be frequent enough for generators which are used as a main source of power. For these, servicing every 250 to 400 running hours is best practice.
For heavy-duty or continuous-use generators, servicing should be carried out after every 200 to 250 hours of operation.
Even generators that rarely run still require routine servicing. Oil degrades over time, while batteries lose charge, seals dry out and fuel can deteriorate. All of these issues can cause major failures, often just when the generator is needed the most.
What Affects Diesel Generator Service Intervals?
While there are plenty of best practice guidelines to follow for generator servicing, there’s no ‘one size fits all’ rule. A number of factors can affect servicing schedules and intervals.
For example:
- Operating hours – the more a generator runs, the faster its components can wear out. This includes parts like filters, belts, injectors and bearings. So the more a generator is used, the more frequently it should be serviced and maintained.
- Type of use – generators supporting critical infrastructure (for example, in emergency healthcare or data centre settings) may need to follow stricter servicing schedules to minimise risk.
- Environmental conditions – generators located in dusty, damp, coastal or extreme temperature environments may suffer from accelerated wear and corrosion.
- Load levels – running consistently under very light load can cause carbon build-up and inefficiency, while heavy loads increase mechanical stress. Both scenarios affect maintenance needs.
- Fuel quality and storage – fuel problems can play havoc with generator systems, causing problems such as blocked filters, injector damage and starting issues. This is why fuel management is a crucial part in determining servicing frequency, as fuel left for too long can easily become contaminated.
- The age and condition of the generator – older generators or those with a history of issues often need closer monitoring and more frequent servicing.
- Manufacturer and warranty requirements – most manufacturers specify minimum service intervals, and it’s important to follow these to avoid invalidating the generator’s warranty or flouting compliance rules.
Recommended Diesel Generator Servicing Schedules
While exact schedules should always be led by the manufacturer’s guidelines, a typical professional servicing programme may include the following:
- All generators – weekly and/or monthly visual inspections, to check oil, coolant and fuel levels. You should also check for warning indicators, fault codes and leaks.
- Backup generators – professional servicing every 6 to 12 months, or after 250 to 500 running hours (whichever comes first)
- Prime power generators – professional servicing every 250 to 400 running hours
- Heavy and/or continuous use generators – professional and extended servicing every 200-250 hours.
It’s also really important to keep records of servicing. It’s good practice in general, but it can also have implications for the warranty of the equipment.
Signs Your Diesel Generator Needs Servicing
Even if you have a planned maintenance schedule in place, there may be times when you need to book in an additional engineer’s visit ahead of time.
You should call in the professionals if you notice any of these signs:
- Difficulty starting or failure to start
- Excessive smoke or unusual exhaust colour
- Fuel, oil, or coolant leaks
- Unusual noises or excessive vibration
- Warning lights, alarms, or fault codes
- Overheating during operation
- Increased fuel consumption
- Poor performance during test runs.
You should also book in a service as a matter of urgency if you can’t find the service records for the equipment. This may happen if you’ve moved onto a new site and a generator is already in situ.
Professional Diesel Generator Servicing Explained
So what actually happens during professional generator servicing? A qualified engineer will usually carry out detailed mechanical and electrical inspections, as well as diagnostic testing and fault analysis.
They’ll also carry out the following:
- Inspecting the fuel system for leaks or contamination
- Inspecting the cooling system, checking coolant levels, hoses, radiator and water pump
- Battery inspection and testing, including charging system checks
- Checking belts, hoses, and pipework for wear or damage
- Checking the exhaust system for leaks, corrosion or potentially dangerous obstructions
- Alternator inspection, including electrical connections and insulation
- Starter motor inspection
- Control panel diagnostics, fault code review and alarm testing
- Safety system checks, including emergency stop functionality
- Load testing or load bank testing (where applicable)
- Cleaning of components and removal of debris or contamination
- Operational test runs to confirm correct starting, running, and shutdown.
At the end of the appointment, you’ll receive a service report for your records.
