Black smoke
Generator Blowing Black Smoke
Black smoke from a diesel generator means the engine is burning more fuel than it has air to burn cleanly, or the combustion is incomplete. It does not prove the injectors have failed. Possible causes include excess fuel, a blocked air filter, an injector fault, overload, a turbo or air-supply problem where the engine has one, poor combustion, an unbalanced load, or a governor that is over-fuelling.
- Smoke is a symptom
- Air and load checked with fuel
- Not an injector quote on sight
- Onsite across Gauteng
Incomplete diesel combustion
What does black smoke from a generator mean?
It means soot: fuel that was not burnt cleanly. The first split is whether the engine is being given too much diesel, or not enough air, or both once a heavy load comes on.
A puff on a cold start that clears is not the same fault as a plume that continues under load. When it happens, and what was switched on, matters more than the colour alone.
White or grey smoke is a different complaint. Unburnt fuel on a cold engine, and coolant in the combustion chamber, are not diagnosed from black soot. Those sit on the white-smoke page.
Air, fuel and load
What causes black smoke from a diesel generator?
Blocked air filter
A choked filter is the simplest air fault. It is inspected before injectors are removed. A dirty filter can smoke a healthy engine.
Injector and fuel problems
A poor spray or a cylinder that is over-fuelling makes soot. That work continues on the injector page after air and load have been considered.
Generator overload
A set asked for more than it can burn cleanly will smoke and may then trip. The connected load and the plate kVA are part of the story.
Poor combustion
Fuel, air and engine condition have to meet. Smoke is the visible result. The cause is still one of those three, not the smoke itself.
Black smoke under load
Acceptable at idle and black once the building connects points at air, fuelling under load, or a set that is too small for the start current.
Black smoke on startup
A short black puff as a cold diesel lights can clear. Smoke that stays after the engine is warm is the fault to book.
Google reviews of ProService Generator Repairs
Google Review
They tuned the mechanical fuel injection on our John Deere generator perfectly, entirely eliminating the black smoke on startup and improving our fuel efficiency dramatically.
Google Review
When our 3-phase diesel plant started smoking, their heavy-plant mechanics traced the issue to a microscopic crack in an injector line and fitted specialized parts within hours.
Common Questions
Questions about black smoke from a generator
What causes black smoke from a diesel generator?
Fuel that is not burning cleanly. Possible causes include too much fuel, not enough air, an injector fault, or an overload.
Is black smoke always the injectors?
No. A blocked air filter or a load the set cannot carry will smoke an engine with healthy injectors.
It only smokes when the load comes on. Why?
The engine is being asked for fuel it cannot burn cleanly at that moment. Air, delivery and the size of the load are checked together.
A puff of smoke on start, then it clears. Is that a fault?
A brief cold puff can be normal. Smoke that continues after the engine is warm should be diagnosed.
Can an overloaded generator blow black smoke?
Yes. Motors starting together, or a board that is larger than the set, can push it into smoke and then a trip.
Is black smoke the same as white smoke?
No. Black is soot from rich combustion. White is more often unburnt fuel, cold running, or, in some cases, coolant. They are not booked as the same fault.
What should I tell you about the smoke?
Whether it smokes at start, at idle, or only under load, and what was switched on when it happened.
Still unsure what the fault is? Call or WhatsApp 082 057 4605 for onsite diagnosis.
Service Areas
Onsite visits across Gauteng
Technicians travel to the generator. These are the main Gauteng areas. Suburb pages sit under each region.
What to send before we attend
ProService Generator Repairs confirms an onsite visit from these details. Send what you have. A missing model number does not stop the booking.
- Location
- The suburb or site, so the visit can be booked in the right area.
- Make and model
- The generator brand and model, if they are known.
- kVA
- The size printed on the data plate.
- Fuel type
- Diesel, petrol, LPG, natural gas, or dual-fuel.
- Controller model
- The module name on the panel, when it is visible.
- Fault or alarm
- What the set does, and any text on the screen.
- Photos
- The generator, the data plate, and the controller or alarm. Send these on WhatsApp.
Book a Visit
Say when the smoke appears
On start, at idle, or only under load. A short description is enough to book the diagnosis.
- Call
- 082 057 4605
- Message us on WhatsApp