Cummins 4BT3.9-G1 Generator Diesel Engine 36 kW Generator Engine Assembly
4-cylinder in-line diesel engine for prime and standby generator sets, supplied as the Cummins 4BT3.9-G1 at 36 kW (48 HP) from 3.9L.
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What This Engine Is Built For
MEP Power supplies the Cummins 4BT3.9-G1 as a complete 4-cylinder in-line generator drive diesel engine of 3.9L running a 102 * 120 mm bore and stroke. It is rated at 36 kW (48 HP). The engine is turbocharged and water cooled, with a BYC A Pump/RSV Governor fuel system. It is built at the Dongfeng Cummins Plant 4BT3.9-G1. Typical duty is prime and standby generator sets; dry weight with flywheel and alternator is 321 Kg and the overall envelope is 867mm*544mm*988mm.
Key Benefits
- Delivers 36 kW (48 HP) from 3.9L as a factory-rated assembly.
- Turbocharged induction with water cooling keeps charge temperature under control in continuous duty.
- Dry weight 321 Kg and envelope 867mm*544mm*988mm are published so the installation can be checked before ordering.
- Starts without auxiliary aids down to -12℃.
- Supplied as a complete engine assembly, so the unit goes straight onto the mounts
- Backed by a written warranty of one year or 1000 hours, whichever comes first
Application Scenarios
- Prime mover for a new generator set build
- Standby set engine replacement
- Rental power fleet rebuild
- Containerised power module
Who It Is For
- Genset packagers matching an engine to an alternator
- Rental power companies rebuilding sets between contracts
- Industrial sites replacing the prime mover in an existing canopy
- Telecom and data infrastructure contractors specifying standby power
Problems It Solves
- An engine that does not hold speed under block load makes the whole set unusable.
- Packagers lose weeks when the engine does not match the alternator and the base frame.
- Standby sets sit idle for months and must still start and take load on demand.
- Identifying the right 4BT3.9-G1 variant from a serial number takes experience; MEP Power checks the configuration before quoting.
Specification As Published
Values below are the published data for this unit. Where a figure is not listed it was not stated by the source data sheet; ask and we will confirm before you order.
| Model | 4BT3.9-G1 (36kw) |
| Type | 4 Cylinders in Line, 4 Stroke Diesel |
| Displacement | 3.9L |
| Bore x Stroke | 102 * 120 |
| Net Weight | 321 Kg |
| Overall Dimension | 867mm*544mm*988mm |
| Manufacturing Plant | Dongfeng Cummins Plant 4BT3.9-G1 |
| Rated Power/Speed | 36 kW/48HP @ 1500 rpm |
| Standby Power | 40 kW/54HP @ 1500 rpm |
| Low Idle Speed | 950-1050 rpm Fuel Consumption @ Running: ≤ 244g/Kw.h 4BT3.9-G1 |
| Aspiration | Turbocharged |
| Fuel System | BYC A Pump/RSV Governor |
| Governor Type | Mechanical, Regulation ≤5% |
| Electrical System (starter motor/alternator) | 12V/24V |
| Lowest Starting Temp (without auxiliary system) | -12℃ |
| Engine Cooling Fluid Volume | 7.2 L |
| Cooling Method | Water Cooled |
Technical Features
- Cylinders: 4 Cylinders in Line, 4 Stroke Diesel
- Displacement: 3.9L
- Bore and stroke: 102 * 120
- Aspiration: Turbocharged
- Fuel system: BYC A Pump/RSV Governor
- Governor: Mechanical, Regulation ≤5%
- Electrical system: 12V/24V
- Coolant capacity: 7.2 L
Quality Control
- Every engine is inspected by the MEP Power inspection team before it leaves the warehouse
- Engine, configuration and serial numbers are recorded and photographed for the buyer
- Genuine and OEM units are quoted separately so the buyer knows exactly what is supplied
- Warranty on genuine and OEM new engines and generator sets is one year or 1000 hours, whichever comes first; parts and repair labour are covered for quality faults inside that period.
Use and Installation Guide
- Quote the model 4BT3.9-G1 when ordering so the correct variant is supplied.
- Match the flywheel and SAE housing to the alternator before assembly
- Set the governor to the frequency required, 50 Hz or 60 Hz
- Run a load bank test before the set goes into service
- Keep the warranty terms in mind: one year or 1000 hours, whichever comes first.
Customisation Options
- OEM and ODM builds, including your logo and company name on the unit
- Cummins engine customisation and modification to your requirement
- Mining and special explosion-proof builds
- Genuine or OEM parts specified on the quotation
How It Compares
| Compared with | What to consider |
|---|---|
| A rebuilt or used engine of the same rating | A rebuilt unit may show the same 36 kW (48 HP) on paper, but its running history is unknown and the warranty rarely covers the whole engine. |
| A larger engine in the same 4BT3.9 range | Moving up a frame size adds weight, envelope and fuel burn; specify the next size up only if the duty cycle really needs the headroom. |
| A non-Cummins engine of similar output | Parts and service for Cummins families are available in most markets, which matters more over ten years than the purchase price on day one. |
4BT3.9-G1 Questions
Is this 4BT3.9-G1 a genuine Cummins engine
What power does the 4BT3.9-G1 produce
What warranty comes with the engine
How do I confirm this is the right variant for my machine
How is the engine shipped and what payment terms apply
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Quote The 4BT3.9-G1
Send your serial number or nameplate photograph and we will confirm the configuration, then price genuine and OEM options side by side.



