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Cummins/Onan 4BT3.9-D(M) Engine Engine

Name: Cummins/Onan 4BT3.9-D(M) Engine
Brand: Cummins/Onan

The Cummins/Onan 4BT3.9-D(M) is a 3.9 L 4-cylinder turbocharged engine rated at 1500 rpm, producing up to 46 kW. It powers generator sets from Cummins/Onan, including the 4BT3.9. It holds 49 L (12.9 gal) of coolant.

Also known as: CUMMINS 4BT3.9-D(M)

Part of the Cummins/Onan 4BT3.9 engine family — 5 variants share parts & fitment.

3.9 L

Displacement

Cylinders

1500 rpm

Rated speed

46 kW

Gross power

Engine specifications

Coolant capacity	49.0 L
Displacement	3.9 L
Cylinders	4
Aspiration	Turbocharged
Rated speed	1500 rpm
Gross power	46 kW

Generator sets powered by this engine

Cummins/Onan 4BT3.9

Common problems

Voltage regulator may require adjustment or is faulty
Cause: Voltage, the voltage regulator may require adjustment or is faulty
Fix: Refer to Tests and Adjustments section for adjustments, replace if faulty.
Shutdown was due to over/under frequency
Cause: If shutdown was due to over/under frequency, the engine governor may require adjustment or is faulty
Fix: Refer to Tests and Adjustments section for adjustments, replace if faulty.
Run RUN
Overvoltage Monitor ES-1859-1
Fix: Shut down the output device and trip an optional circuit breaker
Overload Detector ES-1852
Fix: Shut down the output device
No fault lamp lit
Cause: Possible defective ECM Check fuses F4 and F2 of ECM board A11.
Fix: 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.
K5 - Fault 1 K5 - Fault 1
K4 - Fault 2 K4 - Fault 2
K19 - PLOP K19
K17 - PHET K17
K13 - HET K13
Fault 2 FAULT 2
Fault 1 FAULT 1
Exciter field breaker trips (if equipped)
Cause: 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.
Fix: 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.
AC output voltage too high or low
Cause: 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.
Fix: 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.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan 4BT3.9-D(M).

Parts cataloged across the Cummins/Onan 4BT3.9 family

135

Part #	Description	Category
309-0269	Air Cleaner (Includes Element) - Standard	air_filter
505-0104	Element - Air Cleaner - Heavy Duty Primary [AM# CD1830610826]	air_filter
982-0200	Air Filter	air_filter
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
187-0011	Filter, Fuel	fuel_filter
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
332-0051	Clip, Wire - Fuel Hose---—	hose
503-0183	Clamp, Hose	hose
503-0365	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
187-0015	Filter, Oil	oil_filter
309-0561	Switch, Low Oil Pressure	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
187-0017		other_service
187-0018		other_service
187-0146		other_service
187-0198		other_service
309-0272	Bushing,Reducer - Fluati (1/2NPT x 3/8NPT)	other_service
309-0553	Switch, Temperature	other_service
309-0554	Switch, Temperature	other_service
323-1200	Resistor, Fixed, Wirewound AR	other_service
323-1304	tiotming, Umector	other_service
323-1306	Screw, Cap - Hex Head (1/4-20 x 1/2")	other_service
332-0325		other_service
332-0941	*Tie, Cable	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
332-2921	Switch, Temperature - Washer, Lock (M8)	other_service
333-0291		other_service
333-0292		other_service
3377259	bosch timing tool (ve)	other_service
353-0094		other_service
357-0030	Harness, Wiring - Control Relay Panel (Includes Rectifiers)	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
503-0098	Hose, Drain	other_service
503-0197	503-0197 Miscellaneous Engine	other_service
504-0011	Valve, Shutoff (1/2”)	other_service
505-0026	Coupling, Pipe (1/8")	other_service
505-0050	.-- n.-l. . OW-UUCJI	other_service
505-0098	Band	other_service
505-0185	Adapter, Oil Drain	other_service
505-1373		other_service
526-0008	*Washer, Flat (#10)	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
800-0048	Screw, Cap - Hex Head (3/8-16 x 3/4”)	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	33?-2739	other_service
813-0103	Screw, Machine - Round Head (#10-32 x 3/4º)	other_service
815-0172	Cover, Adapter Outlet	other_service
850-0025	Screw, Machine - Round Head (#8-32 x 3/8" )	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	Washer, Lock - Spring (M8)	other_service
850-2012	Washer, Lock - Spring (M12)	other_service
856-0013	Washer	other_service
860-2007	Screw, Machine - Round Head (M10 x 32 x 3/4")	other_service
870-0053	(350-0030	other_service
870-0131	Nut, Hex - w/ET (#10-32) Breaker, Circuit 60 Hertz	other_service
870-0212	Nut, Locking (1/4-20)	other_service
871-0010	#Nut	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
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
750-1010	Screw, Machine - Fillister Head (1/4-20 x 1")	screw
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
505-0059	Sensor, Water Pressure	sensor
405-3826-01	Support, Engine - Screw, Cap - Hex Head (M12 x 1.75 x 65mm)	support
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.

Common questions

What is the displacement of the Cummins/Onan 4BT3.9-D(M)?

The Cummins/Onan 4BT3.9-D(M) has a displacement of 3.9 liters with 4 cylinders.

Which generators use the Cummins/Onan 4BT3.9-D(M) engine?

The Cummins/Onan 4BT3.9-D(M) powers 1 generator set(s), including Cummins/Onan 4BT3.9.

What is a common problem with the Cummins/Onan 4BT3.9-D(M) engine?

A commonly reported issue on generators using the Cummins/Onan 4BT3.9-D(M) is: Voltage regulator may require adjustment or is faulty. Cause: Voltage, the voltage regulator may require adjustment or is faulty. Fix: Refer to Tests and Adjustments section for adjustments, replace if faulty..