Generator brands · Engines
Repairs and Servicing for Doosan-Engined Generators
We repair, service and maintain generator sets with Doosan engines on site across Gauteng, whichever builder’s name is on the canopy. Doosan diesels are common in mid-to-large standby and prime sets for offices, retail centres, factories and construction sites, from roughly 150 kVA to the high hundreds of kVA. Typical faults involve speed control, the air and fuel supply or cooling, and each is diagnosed on the engine before parts are ordered.
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Doosan engines in generator sets
Doosan’s industrial diesels are fitted by many generator builders in the mid-to-large range. The canopy usually carries the builder’s name: builders including Himoinsa and SDMO have used Doosan engines in some of their ranges, alongside many smaller assemblers. The engine data plate is where the make and model are confirmed.
Older sets can carry engines badged Daewoo, the company whose engine business Doosan took over. The engine business has since changed hands again, so a newer engine of the same family may show a different company name. Either way, the model code and serial number on the plate identify it.
Towable mobile generators for construction sites have also been sold under the Doosan name. Like Atlas Copco mobile sets, they get the same engine and alternator care as a fixed set, plus the checks a towed unit needs: sockets and earth leakage protection, the drawbar, wheels and tyres, and fuel that may have been stirred up on the road.
Doosan engine families you may find
| Engine layout | Model examples | Where they are used |
|---|---|---|
| In-line six, turbocharged and intercooled | Model examplesP086TI, P126TI and their DP-series versions | Where they are usedMid-size standby and prime sets, roughly 150 to 400 kVA, for offices, retail centres and factories |
| V8, V10 and V12 | Model examplesP158LE, P180LE, P222LE and their DP-series versions | Where they are usedLarge sets, roughly 400 to 800 kVA, for industrial sites, hospitals and large buildings |
| Older Daewoo-badged engines | Model examplesIdentified from the engine plate | Where they are usedOlder standby sets still in service |
TI in a model code marks a turbocharged, intercooled engine.
Air and fuel
Charge-air pipework, fuel filters and the injection pump
Most Doosan generator engines are turbocharged and intercooled: the turbocharger compresses the intake air, a charge-air cooler cools it, and it is fed to the cylinders. A leak anywhere in that path, from a split hose, a loose clamp or a cracked pipe, means less air for the fuel being injected. The result is black smoke, lost power and hotter exhaust under load.
Highveld dust makes it worse: a neglected air filter loads up quickly, and a damaged element or loose intake joint lets grit through to the turbocharger. Long runs at light load cause the opposite problem: oil past the turbocharger seals and unburnt fuel in the exhaust, a form of wet stacking.
On the fuel side, many versions use a mechanical injection pump with the governor or speed actuator mounted on it, fed through water separators and filters. Fuel delivery and speed control are therefore closely linked, which is why a speed fault is traced from the fuel supply first.
The photo shows the fuel filter, injection pump and governor linkage on a generator diesel. It illustrates the parts described here and is not presented as a Doosan engine.
- Charge-air leaks: black smoke and low power
- Air filter restriction checked at every service
- Fuel filters and pump linkage checked before any speed setting
Speed control
Tracing a speed or frequency fault
- 01
Fuel supply first
A partly blocked filter, a joint drawing air or a weak lift pump starves the engine as load rises, and makes speed control look faulty.
- 02
Speed signal
Electronic control reads engine speed from a magnetic pickup on the flywheel housing. A dirty, loose or badly gapped pickup gives an unsteady signal and an unsteady engine.
- 03
Actuator and linkage
The actuator and its link to the pump must move freely. Wear or binding causes hunting that no setting will cure.
- 04
Controller settings
Gain and stability are set at no load, then checked as load is added and removed, so the engine returns to 50 Hz without overshooting.
- 05
Proof under load
Frequency and voltage are checked through load steps. Most AVRs lower the voltage when speed falls, to protect the alternator, so a speed fault often shows as a voltage problem too.
Other faults on Doosan-engined sets
| Symptom | Likely causes | Repair route |
|---|---|---|
| Low power and black smoke under load | Likely causesBlocked air filter, charge-air leak, turbocharger wear, injectors or injection timing | Repair routeSmoke |
| High coolant temperature on long runs | Likely causesDust-blocked radiator, slack belt, sticking thermostat or low coolant | Repair routeOverheating |
| Oil and fuel weeping around the engine | Likely causesGaskets, seals and fuel line joints aged by heat and vibration | Repair routeLeaks |
| Low oil pressure alarm or shutdown | Likely causesA genuinely low level or pressure, or a failed sender or damaged wiring | Repair routeLow oil pressure shutdown |
| Engine alarm with no obvious fault | Likely causesSensor, wiring or controller setting faults | Repair routeControl panel repairs |
Servicing a Doosan engine
Tasks and intervals come from the engine’s maintenance schedule, by running hours or by time. A typical service covers:
- Engine oil and filters, with the oil grade matched to the engine
- Fuel filters replaced and water separators drained
- Air filter restriction checked and the element replaced as needed
- Intercooler, charge-air hoses and clamps inspected
- Coolant strength and condition, radiator core, fan and belts
- Speed control checked at no load and under load
- Exhaust, turbocharger play and oil leaks
- Batteries, charger, starter and the controller’s protections tested
- A run under load, on the building load or a load bank
Parts are chosen from the engine data plate and serial number: genuine or quality-equivalent parts made to the same specification, as suits the job. Less common parts for older engines can take time to source, and the quote says so.
Independent service
We Service & Repair All Generator Brands
Onsite Generator Repairs is an independent generator specialist. We repair, service and maintain Doosan equipment as part of our work on every make of generator.
Manufacturer warranty claims go through the manufacturer’s own network. If your generator is still under warranty, check the warranty terms before arranging work by anyone else.
Brand names and trademarks belong to their respective owners. Onsite Generator Repairs is an independent service and repair company.
Service areas
Where we work in Gauteng
FAQ
Frequently asked questions
My generator has another brand’s name but a Doosan engine. Who services it?
We do. The engine is looked after to its own maintenance schedule, while the builder’s alternator, controller, canopy and fuel tank are checked in the same visit.
Why does my Doosan-engined set hunt at no load but run fine under load?
Hunting at light load usually points to speed controller or actuator settings, or a small fuel supply restriction. It is worth fixing: hunting stresses the engine and can upset sensitive equipment. See frequency and speed problems.
Where do I find the engine model?
On the engine’s own data plate, usually on the block or the rocker cover. It gives the model and serial number; a clear photo of it, the set’s nameplate and the hour meter lets us prepare before the visit.
Can parts still be found for older Doosan or Daewoo engines?
Service parts such as filters and belts are widely available for the common models. Major parts for older engines can take longer, so the engine is identified early and lead times are given on the quote.
How often should a Doosan-engined standby set be serviced?
At least once a year, and sooner if the hour meter reaches the interval in the engine’s maintenance schedule, which can happen within months during heavy load shedding. A maintenance plan keeps track of both, and generator repairs cover anything a service turns up.
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