The Cummins/Onan 4BT3.9 is a 3.9 L 4-cylinder engine, producing up to 150 kW. It powers generator sets from Cummins/Onan, including the 4BT 3.9, DGBC, DGCA and DGCB. It holds 17.7 L (4.7 gal) of coolant.
Also known as: Cummins 4BT3.9
Part of the Cummins/Onan 4BT3.9 engine family — 9 variants share parts & fitment.
| Coolant capacity | 17.7 L |
|---|---|
| Displacement | 3.9 L |
| Cylinders | 4 |
| Gross power | 150 kW |
| Code | Meaning | Remedy |
|---|---|---|
| RUN | Run | |
| FAULT 1 | Fault 1 | |
| FAULT 2 | Fault 2 | |
| K13 | K13 - HET | |
| K4 - Fault 2 | K4 - Fault 2 | |
| K5 - Fault 1 | K5 - Fault 1 | |
| K17 | K17 - PHET | |
| K19 | K19 - PLOP | |
| ES-1859-1 | Overvoltage Monitor | Shut down the output device and trip an optional circuit breaker |
| ES-1852 | Overload Detector | Shut down the output device |
| Symptom | Cause | Remedy |
|---|---|---|
| Voltage regulator may require adjustment or is faulty | Voltage, the voltage regulator may require adjustment or is faulty | Refer to Tests and Adjustments section for adjustments, replace if faulty. |
| Shutdown was due to over/under frequency | If shutdown was due to over/under frequency, the engine governor may require adjustment or is faulty | Refer to Tests and Adjustments section for adjustments, replace if faulty. |
| No fault lamp lit | Possible defective ECM Check fuses F4 and F2 of ECM board A11. | Perform restart and check for B+ voltage in at TB1-9 and voltage out at TB1-10 to fuel solenoid. If there is voitage out at TB1-10, check fuel supply solenoid, shutoff valves, etc. If there is no voltage out at TB1-10, ECM board A11 is defective. Replace. |
| AC output voltage too high or low | Is engine running at correct rpm? No; Are generator output connections correct and secure? Yes; Does adjustment of Voltage Adjust control R21 (if equipped) result in correct output voltage? No; Check Voltage Regulator Adjustment. Check ok? No; Check condition of rotating diodes. | Visually inspect for loose connections, faulty diodes, etc. Check ok? Yes; Do not replace Voitage Regulator Replace Voltage Regulator VR21. ACAUTION VR21 until external trouble has been corrected to avoid possible damage to new regulator board. |
| Exciter field breaker trips (if equipped) | Does AC output voltage build up to 150% or more of rated voltage before breaker trips? No; Check diodes in rotor assembly. Replace if bad. | Check Voltage Regulator adjustments and connections. Check generator stator leads for proper, secure connection. Refer to appropriate electrical schematic. Check exciter rotor winding. Replace if bad. Check generator rotor field winding. Replace if bad. Check generator stator windings. Replace if bad. Do not replace Voltage Regulator Replace Voltage Regulator VR21. ACAUTION VR27 until external trouble has been corrected to avoid possible damage to new regulator board. |
Fault codes and symptom→remedy steps extracted from this engine’s service/owner documentation; verify against the official manual before servicing.
| Part # | Description | Category |
|---|---|---|
| 140-0710 | Air Cleaner, Standard | air_filter |
| 309-0272 | Air Cleaner - Heavy Duty (10" Inlet Tube) | air_filter |
| 505-0104 | air_filter | |
| 982-0200 | Air Filter | air_filter |
| AN500T0083 | ALTERNATOR | alternator |
| 150-2007 | Guard. Belt Screw. Cap - Hex Head (1/2-13 X 2-1/4“) | belt |
| 187-0008 | Belt, Drive | belt |
| 353-0094-01 | Connector Housing and Contact Pins, 8 Pin (Less Pins) | connector |
| 3824469 | fuel pump gear puller | fuel_pump |
| 102-1147 | Gasket, Drain - Oil Pan | gasket |
| 187-0002 | Gasket Kit, End - Top | gasket |
| 187-0012 | Gasket, Cover - Valve | gasket |
| 526-0018 | Gasket, Flange (1-3/4) | gasket |
| DM-3801371 | Gasket Set - 4BT 3.9 | gasket |
| FP-4B39PREM | 4B/4BT3.9 In-Frame Kit w/upper gasket set & oil pan gasket | gasket |
| FP-4B39PREML | 4B/4BT3.9 In-Frame Kit w/upper gasket set & oil pan gasket (late) | gasket |
| FP-IFK4B39PREM | 4B/4BT3.9 In-Frame Kit w/upper gasket set & oil pan gasket | gasket |
| FP-IFK4B39PREML | 4B/4BT3.9 In-Frame Kit w/upper gasket set & oil pan gasket (late) | gasket |
| 503-0365 | Heater, Engine - 750 Watt (120 volt) | heater |
| 332-0051 | Clip, Wire - Fuel Hose---— | hose |
| 503-0098 | Hose, Oil Drain - Bulk (3/4 | hose |
| 503-0183 | Clamp, Hose | hose |
| 503-0685 | Clamp, Hose | hose |
| DM-3805455 | Oil Cooler Hose - 4BT 3.9 | hose |
| 3822509 | injector puller | injector |
| 3823276 | injector bore brush | injector |
| DM-3029550 | Fuel Injector - 4BT 3.9 | injector |
| 140-2164 | Nut, Square (1/4-20) | nut |
| 140-0705 | Oil Filter | oil_filter |
| 102-1237 | Adapter, Oil Drain (Ml8 x 1/2") (S2) | other_service |
| 145-0596 | other_service | |
| 150-2187 | Lever, Actuator - Governor | other_service |
| 150-2203 | other_service | |
| 150-2218 | other_service | |
| 150-2251 | Joint, Ball | other_service |
| 151-0611 | Control, Governor | other_service |
| 151-0632 | other_service | |
| 154-2581 | other_service | |
| 155-2062 | other_service | |
| 155-2080 | other_service | |
| 155-2175 | Clamp, Muffler 4" | other_service |
| 155-2256 | other_service | |
| 155-2353 | other_service | |
| 187-0004 | other_service | |
| 187-0007 | other_service | |
| 187-0011 | Filter, Fuel | other_service |
| 187-0015 | Filter, Oil | other_service |
| 187-0017 | other_service | |
| 187-0018 | other_service | |
| 187-0146 | other_service | |
| 187-0198 | other_service | |
| 309-0553 | other_service | |
| 309-0554 | other_service | |
| 323-1304 | tiotming, Umector | other_service |
| 332-0325 | other_service | |
| 332-0941 | other_service | |
| 332-1087 | other_service | |
| 332-1279 | Insulated | other_service |
| 332-1445 | Tie, Cable 18 98-5219 1 Decal - Panel Front (Not I l l u s t r a t e d ) 19 98-5220 1 Decal | other_service |
| 332-2739 | Bracket | other_service |
| 333-0291 | other_service | |
| 333-0292 | other_service | |
| 3377259 | bosch timing tool (ve) | other_service |
| 353-0094 | other_service | |
| 357-0030 | RECTIFIER ‘BATT CHARGING | other_service |
| 416-0446 | Cable, Battery (#2/0) 12-1/2" (Jumper) | other_service |
| 416-0893 | other_service | |
| 416-0921 | other_service | |
| 501-0441 | Line, Fuel - Flex (Fuel In) | other_service |
| 501-0502 | Line, Fuel - Flex (Fuel out) | other_service |
| 503-0197 | other_service | |
| 504-0011 | Valve, Shutoff (1/2”) | other_service |
| 505-0026 | Coupling, Pipe (1/8") | other_service |
| 505-0050 | Nut, Cap - Hex Head (#10-32 x 30mm) | other_service |
| 505-0059 | other_service | |
| 505-0098 | Band | other_service |
| 505-0185 | other_service | |
| 505-1373 | other_service | |
| 526-0008 | other_service | |
| 526-0115 | Washer (5/16 “) | other_service |
| 526-0196 | Washer, Spacer - Shield JC)INT, BALL LINKAGE | other_service |
| 526-0327 | other_service | |
| 800-0012 | Screw, Cap - Hex Head (1/4-20 x 2-1/4”) Begin Spec C MANIFOLD KIT, INTAKE | other_service |
| 800-1003 | other_service | |
| 800-2060 | 016-40820 NE 1 Screw. Cap - Hex Head (M8-1.25 x 35MM) 3 856-0008 | other_service |
| 800-2110 | Hood, Inlet - Air Molded | other_service |
| 800-2112 | Screw. Cap - Hex Head (M12 x 30nin) | other_service |
| 812-0075 | other_service | |
| 813-0103 | other_service | |
| 815-0172 | Cover, Adapter Outlet | other_service |
| 850-0025 | other_service | |
| 850-0030 | Washer, Lock - Spring (#10) | other_service |
| 850-0050 | Washer, Lock - Spring (3/8”) | other_service |
| 850-2006 | Washer, Lock - Spring (M6) | other_service |
| 850-2008 | Heater, Engine Coolant | other_service |
| 850-2012 | Washer, Lock - Spring (M12) | other_service |
| 856-0013 | other_service | |
| 860-2007 | Screw, Machine - Round Head (M10 x 32 x 3/4") | other_service |
| 870-0053 | other_service | |
| 870-0131 | other_service | |
| 870-0212 | Nut, Locking (1/4-20) | other_service |
| 871-0010 | ENut, Hex (10-32) ‘853-0006 Elackwasher 526-004$ | other_service |
| 871-0028 | other_service | |
| 928-0502B | other_service | |
| 928-0506 | other_service | |
| 960-0135 | other_service | |
| 960-0136 | Battery, 24V, 55Ah, AGM | other_service |
| 960-0242 | other_service | |
| 960-0504A | other_service | |
| 960-0505 | other_service | |
| 960-12 | other_service | |
| 965-0520 | Cooling Fan | other_service |
| DM-3802010 | Main Bearing Set Standard - 4BT 3.9, 6BT 5.9, 6CT 8.3 | other_service |
| K19-CP | 460 kWe | other_service |
| K38-CP | 920 kWe | other_service |
| K50-CP | 1240 kWe | other_service |
| 110-0426 | Water Pump | pump |
| 187-0001 | Pump, Water | pump |
| 187-0013 | Pump, Transfer - Fuel | pump |
| 187-0020 | Pump, Injection | pump |
| DM-3004242 | Fuel Transfer Pump - 4BT 3.9 | pump |
| DM-3805403 | Water Pump - 4BT 3.9, 6BT 5.9 | pump |
| DM-3807788 | Oil Pump - 4BT 3.9 | pump |
| 323-1200 | Resistor, Fixed, Wirewound AR | resistor |
| 323-1306 | Screw, Cap - Hex Head (1/4-20 x 1/2") | screw |
| 750-1010 | Screw, Machine - Fillister Head (1/4-20 x 1") | screw |
| 800-0048 | Screw, Cap - Hex Head (3/8 - 16 X 3/4") | screw |
| 110-0430 | Seal, Water Pump | seal |
| 150-2201 | Sensor, Speed – Magnetic | sensor |
| 193-0244 | Sender, Oil Pressure (E1) | sensor |
| 193-0353 | Sender, Temperature - Oil | sensor |
| 193-0375 | # Sender, Water Temperature | sensor |
| 405-3826-01 | Support, Engine - Screw, Cap - Hex Head (M12 x 1.75 x 65mm) | support |
| 309-0269 | Air Cleaner (Includes Element) - Standard | switch |
| 309-0561 | Switch, Temperature - Washer, Lock (#10) | switch |
| 332-2921 | Switch, Temperature - Washer, Lock (M8) | switch |
| 187-0009 | Thermostat | thermostat |
| 187-0010 | Gasket, Thermostat | thermostat |
| 821-0018 | Thermostat (Includes Plugs) | thermostat |
| DM-3015282 | Thermostat 180F - 4BT 3.9, 6BT 5.9 | thermostat |
Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.
The Cummins/Onan 4BT3.9 has a displacement of 3.9 liters with 4 cylinders.
The Cummins/Onan 4BT3.9 powers 4 generator set(s), including Cummins/Onan 4BT 3.9, Cummins/Onan DGBC, Cummins/Onan DGCA, Cummins/Onan DGCB.