1. Generator Won't Start
This is the most common complaint we receive. A generator that cranks but won't fire up, or one that doesn't respond at all, usually has one of these causes:
- Dead or weak battery – The most frequent cause, especially for standby generators that sit idle for long periods. Regular battery checks and maintenance charging are essential.
- Faulty starter motor – If you hear a clicking sound but the engine doesn't turn, the starter motor may be failing.
- Fuel starvation – A blocked fuel filter, airlock in the fuel line, or a faulty fuel lift pump prevents fuel reaching the injectors.
- Glow plug failure (cold weather) – Diesel engines need heat to ignite. Failed glow plugs cause hard starts in cooler conditions.
- Low oil pressure cutout – Safety sensors shut the generator down if oil pressure drops below safe limits.
Solution: Regular servicing catches most of these before they become problems. If your generator won't start, call our Nairobi team for same-day emergency diagnosis.
2. Generator Runs But Produces No Power
This is perhaps the most alarming fault — the engine runs perfectly, but there's no electricity output. The causes are almost always in the electrical generation side:
- AVR (Automatic Voltage Regulator) failure – The AVR controls the generator's output voltage. When it fails, there's often no output at all. Replacement is usually the fix.
- Alternator winding fault – Open circuit or short circuit in the alternator windings prevents power generation.
- Lost residual magnetism – Alternators need residual magnetism to self-excite. This can be lost after a heavy fault. The fix is "flashing" the alternator.
- Tripped circuit breaker – Sometimes the simplest answer. Check if the main circuit breaker has tripped.
3. Generator Overheating
Overheating triggers the generator's temperature protection, causing automatic shutdown. In Kenya's warm climate, generators need to be watched carefully for cooling issues. Common causes:
- Low coolant level – Coolant leak or evaporation reducing the cooling capacity
- Blocked or dirty radiator – Dust and debris restricting airflow through the radiator
- Faulty water pump – Not circulating coolant effectively
- Thermostat stuck closed – Prevents coolant circulation
- Generator room with poor ventilation – Very common in Nairobi's industrial buildings
- Running beyond rated load for extended periods
Prevention tip: Ensure your generator room has adequate ventilation. Radiator inlet air should come in at one end, with hot exhaust air leaving at the other — never recirculating.
4. Excessive Black Smoke
Black exhaust smoke from a diesel generator indicates incomplete combustion. The engine is getting too much fuel relative to air. Common causes:
- Blocked air filter – Very common in dusty Kenyan industrial environments. Restricts intake air.
- Faulty or worn fuel injectors – Spraying too much fuel or poor atomisation
- Turbocharger failure – Reduces the amount of air pushed into the engine
- Overloading – Generator running above its rated capacity
- Wrong fuel – Using the wrong grade of diesel
5. Generator Trips Frequently Under Load
If your generator starts fine but keeps tripping off when you connect loads, the problem is usually:
- Generator is undersized for the load being connected
- Overload protection tripping due to excessive starting currents (especially motors and compressors)
- Earth fault protection detecting a wiring problem in the connected installation
- Voltage or frequency instability causing sensitive loads to trip
6. Voltage Fluctuation
Unstable voltage is dangerous for connected equipment. Sensitive electronics, motors, and medical equipment are at risk. Causes include a failing AVR, governor problems, or fuel supply issues causing the engine speed to vary.
Experiencing Any of These Problems?
Our Nairobi-based technicians are available 24/7 for emergency generator repair across Kenya. Don't run your generator in a fault condition — it can cause further, more expensive damage.
When to Call a Professional Generator Technician
Some checks — battery voltage, oil level, coolant level, air filter condition — can be done by your maintenance team. But for any electrical faults, engine internal problems, injector issues, or alternator repairs, always use a qualified diesel generator technician.
Attempting generator electrical repairs without the right training and equipment can result in serious injury or further, more expensive damage to your generator.
Steve Roberts Generators has been repairing diesel generators in Nairobi, Mombasa, and across Kenya for over 9 years. Our technicians carry the tools, test equipment, and genuine spare parts to diagnose and fix most generator faults in a single visit.