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Cummins/Onan 4BT3.9 Engine

The Cummins/Onan 4BT3.9 is a 3.9 L 4-cylinder engine. It powers generator sets from Cummins/Onan, including the DGCA and DGCB. It holds 11 L (2.9 gal) of oil and 21 L (5.5 gal) of coolant.

Also known as: Cummins 4BT3.9

Part of the Cummins/Onan 4BT3.9 engine family — 8 variants share parts & fitment.

3.9 L

Displacement

Cylinders

11.0 L

Oil capacity

On this pageSpecs Generator sets Maintenance FAQ Service intervals Torque & specs Fluids Fault codes Procedures Wiring

Engine specifications

Oil capacity	11.0 L
Coolant capacity	21.0 L
Displacement	3.9 L
Cylinders	4

Generator sets powered by this engine

Cummins/Onan DGCA Cummins/Onan DGCB

How to read your Cummins/Onan engine serial & model number →

Common problems

Engine cranks but will not start
Cause: Empty fuel tank, fuel leaks, or plugged fuel lines
Fix: Correct as required
The FAULT 1 or FAULT 2 fault lamp lights. Engine shuts down immediately, engine runs for several seconds and then shuts down, or engine continues to run FAULT 1
Cause: The standard undesignated fault functions are programmed to shut down the set when a fault is sensed. Fault 1 is time delayed while Fault 2 is immediate. The nature of the fault is an optional selection that is determined when the set installation is designed. The undesignated fault functions may also be programmed for non-shutdown or non-time delay.
Over Current 1471
Low Coolant Level 197
Cause: Engine coolant level has fallen below the warning trip point
Fix: If generator is powering critical loads and cannot be shut down, wait until next shutdown period, then follow code 235 procedure; if engine can be stopped, follow code 235 procedure.
Weak Battery — Indicates that during cranking, the battery voltage is at or below the weak battery warning trip point for a time greater than or equal to the weak battery set time. 1442
Cause: During cranking, the battery voltage is at or below the weak battery warning trip point for a time greater than or equal to the weak battery set time
Fix: See code 441 for corrective action
Weak Battery 1442
Cause: During cranking, the battery voltage is at or below the weak battery warning trip point for a time greater than or equal to the weak battery set time
Fix: See code 441 for corrective action.
Under Frequency 1448
Too Long In Idle — Indicates genset has been in Idle mode too long (10 minutes maximum). 2342
Cause: Genset has been in Idle mode too long (10 minutes maximum)
Too Long In Idle (10 min.) 2342
SWITCH OFF lamp flashes
Cause: Run/Stop/Remote switch is in the Stop position which will prevent automatic starting if an automatic transfer switch is used
Fix: Move the Run/Stop/Remote switch to the Remote position for automatic starting.
Speed/Hz Match 1469
Speed Signal Lost — Battle Short is suspended and a shutdown occurs immediately. 121
Speed Signal Lost 121
Shutdown After BS 1123
Shutdown After Battle Short 1123
Cause: Moving the customer installed Battle Short switch to OFF with an active but overridden shutdown fault or a shutdown fault that was overridden at any time.

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

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Battery	1.225		—

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.

Repair guides

Step-by-step procedures compiled from the Cummins/Onan service manual for this engine.

Service intervals

Item	Action	Hours	Months	Notes
Charge air piping	Check	50 hr		Daily or after 8 hours
Coolant level	Check	8 hr		Daily or after 8 hours
Engine oil level	Check	8 hr		Daily or after 8 hours
Fuel Filter(s)	Drain	8 hr		Drain 1 cup or more of fuel to remove water and sediment. Refer to engine operation and maintenance manual for procedure.
Fuel Tanks (water and sediment)	Drain	8 hr		Drain 1 cup or more of fuel to remove water and sediment.
Fuel level	Check	8 hr		Daily or after 8 hours
General genset inspection	Inspect	8 hr		Daily or after 8 hours. Check for oil, fuel, cooling and exhaust system leaks; check exhaust audibly and visually with set running.
Inspect Genset	Check	8 hr		Check for oil, fuel, cooling and exhaust system leaks. Check exhaust system audibly and visually with set running and repair any leaks immediately.
Oil Level	Check	8 hr		Keep oil level near the dipstick high mark without overfilling.
Air Cleaner	Clean	50 hr		Clean if required. Perform more often in dusty conditions.
Air cleaner (clean if required)	Clean	50 hr		Weekly or after 50 hours; perform more often in dusty conditions
Battery charging system	Check	50 hr		Weekly or after 50 hours
Coolant heater	Check	50 hr		Weekly or after 50 hours
Crankcase Oil	Drain	50 hr		First service — Break-in: drain and replace the crankcase oil after the first 50 hours of operation on new generator sets.
Engine oil and filter	Change	50 hr		First service — Drain and replace crankcase oil after first 50 hours on new generator sets
Exhaust condensate trap	Drain	50 hr		Weekly or after 50 hours
Water and sediment from fuel tank	Drain	50 hr		Weekly or after 50 hours; drain 1 cup or more of fuel to remove water and sediment
Radiator hoses for wear and cracks	Inspect	100 hr		Monthly or after 100 hours
Starting batteries	Check	100 hr		Monthly or after 100 hours
Battery electrolyte level	Check	200 hr		Check at least every 200 hours of operation
Anti-freeze and DCA Concentration	Check	250 hr	3 mo	Refer to engine operation and maintenance manual.
Crankcase oil and filter	Change	250 hr	12 mo	Refer to Cummins Engine Operation and Maintenance Manual. Standby applications: change every 12 months or 250 hours, whichever comes first.
Drive Belt Tension	Check	250 hr	3 mo	Visually check belt for evidence of wear or slippage. Replace if hard or brittle. Refer to engine operation and maintenance manual.
Fuel Filters	Change	250 hr	3 mo	Refer to engine operation and maintenance manual.
Governor Adjustment	Check	250 hr	3 mo
Radiator Hoses for Wear & Cracks	Check	250 hr	3 mo
Coolant Filter	Change	500 hr	6 mo	Refer to engine operation and maintenance manual.
Cooling System	Clean	500 hr	6 mo	Refer to engine operation and maintenance manual.
Crankcase Breather	Clean	500 hr	6 mo	Refer to engine operation and maintenance manual.
Generator bearing	Inspect	1000 hr		Inspect for wear every 1000 hours by an Onan Distributor
Valve Lash	Adjust	1000 hr		After 1000 hours; contact an authorized service center for service
Alternator Bearings	Inspect	4000 hr	24 mo	Inspect all sealed bearings every 4000 to 4500 hours (10000 hr/2 years)
Generator bearing	Replace	10000 hr	24 mo	Prime power: every 10,000 hours or after two years; standby power: every five years
Alternator Bearings	Replace	30000 hr	60 mo	Replace all sealed bearings every 30000 hr/5 years (or if necessary after 10000 hr/2 years)
Air cleaner element	Change	500 hr	12 mo	Yearly or sooner if service indicator pops up
Air cleaner element	Replace		12 mo	Replace yearly or sooner if service indicator pops up; more often in dusty conditions
Generator set exercise	Test		1 mo	Exercise at least once a month for a minimum of 30 minutes at not less than 30 percent of nameplate rating

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Service specifications

Type	Item	Value	Unit	Condition
Clearance	Float switch lift below C-clip stop	1/8	inch (3 mm)
Clearance	Overspeed switch magnet-to-fly arm air gap (minimum)	0.005	inches (0.13 mm)
Gap	Mechanical overspeed switch air gap between magnet and fly arm (replace switch if less)	0.005	inches (0.13 mm)
Gap	Overspeed switch air gap	0.005 in. / 0.13 mm	in / mm
Other	AVR DROOP preset at factory	five percent droop at full load and zero power factor
Other	Battery electrolyte corrected specific gravity (fully charged)	1.260		electrolyte temperature corrected
Other	Battery electrolyte specific gravity, fully charged (corrected)	1.260		corrected to 80 °F (27 °C)
Other	Battery recharge threshold specific gravity	1.215
Other	Battery specific gravity recharge threshold	1.260	specific gravity	recharge if below
Other	Battery specific gravity temperature correction	four gravity points (0.004) for every ten degrees above 80 F (27 C)
Other	Battery specific gravity, fully charged	approximately 1.260	at 80°F (27°C)
Other	Coolant level below radiator cap opening	2	inches
Other	Cycle crank crank and rest time	7 to 20	seconds
Other	Cycle crank number of cycles	3, 4, or 5
Other	Cycle cranking option	15	seconds	15 s crank, 15 s rest, 3 cycles
Other	ECM fuse F1 (starter solenoid circuit)	20	amps
Other	ECM fuse F2 (fuel solenoid circuit)	20	amps
Other	ECM fuse F3 (continuous B+ to remote circuits)	15	amps
Other	ECM fuse F4 (ECM circuits)	5	amps
Other	ECM fuse F5 (engine gauge circuits)	5	amps
Other	Frequency adjustment range	±5%	%	genset running
Other	Fuse A31-F1 (control B+)	5	Amp	Engine Interface board
Other	Fuse A31-F3 (auxiliary B+)	5	Amp	Engine Interface board; panel lights, run and start relays
Other	Fuse A38-F1 (Network B+)	10	Amp	Governor Output Module
Other	Fuse A38-F2 (Switched B+)	10	Amp	Governor Output Module
Other	Fuse A38-F3 (Governor B+)	10	Amp	Governor Output Module
Other	Fuse TB-Bat F1 (Customer B+)	20	Amp	Engine Harness Assembly
Other	GOV RAMP adjustment range	0 through 10	seconds
Other	Generator voltage adjustment range via rheostat R21	+/-3 percent of rated nameplate voltage	percent
Other	Governor droop adjustment range	within 5	percent of nominal frequency (3 Hz for 60Hz sets, 2.5 Hz for 50Hz sets)
Other	LOP and HET fault time delay following starter disconnect	about 10 seconds	seconds
Other	Low oil pressure / high engine temperature fault time delay	about 10	seconds	following starter disconnect and inhibited during cranking
Other	Over/under voltage module time delay (to prevent nuisance tripping)	25 percent, or approximately 2.5 seconds	percent / seconds
Other	Overcrank cranking limit	75	seconds	standard overcrank control
Other	Overcrank limit (Sentinel)	60	seconds
Other	Overcrank limit (three 15-second cranking cycles with two 15-second rest periods)	75 seconds	seconds
Other	Overcrank option limit (Detector)	75	seconds
Other	Overspeed module time delay	typically one second	seconds
Other	Overspeed warning range 60 Hz sets	2000 to 2200	RPM
Other	REG VHZ adjustment range	1 through 50 (normal range 7 through 21)
Other	Response jumper setting - 90 to 550 kW	B to C
Other	Response jumper setting - over 550 kW	A to B
Other	Response jumper setting - under 90 kW	A to C
Other	Setup/calibration menu access code	574
Other	Standard cycle cranking (Detector)	three 15-second cranking cycles with two 15-second rest periods
Other	Start delay adjustment range	0 to 300	seconds	remote starting in Auto mode
Other	Stop delay adjustment range	0 to 600	seconds	remote stopping in Auto mode
Other	Time delayed start / time delayed stop adjustment range	1 to 15 seconds (start); 1 to 15 seconds (stop); cool-down 3-5 minutes recommended	seconds / minutes
Other	Trailer brake shoe adjustment back-off	10	clicks
Other	Trailer surge brake actuator stroke length (service brakes if exceeds)	1	inch (25 mm)
Other	Under-frequency roll-off (UFRO) threshold, 50 Hz applications	49	Hz
Other	Under-frequency roll-off (UFRO) threshold, 60 Hz applications	59	Hz
Other	Voltage adjustment range	±5%	%	genset running
Pressure	Engine oil pressure (normal)	30 to 65	psi (207 to 449 kPa)	at normal operating temperature
Pressure	Engine oil pressure range (low oil pressure troubleshooting)	25 to 65	psi (172 to 449 kPa)
Pressure	Fuel shutoff valve rating (TB1-8 and TB1-5)	not more than 0.5	amps	120 or 240 VAC
Pressure	Idle oil pressure	10 - 30	psi (69 - 207 kPa)	idle
Pressure	Idle oil pressure	10-30	psi (69-207 kPa)	idle
Pressure	Idle oil pressure	69-207	kPa	idle
Pressure	Idle oil pressure (normal)	10-30	psi (69-207 kPa)	Engine model 6C, idle

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Recommended fluids

Fluid	Grade	Standard	Ambient	Capacity	Notes
Coolant		soft water/E.G./DCA mixture			Installation review checklist item: cooling system must be filled with soft water/E.G./DCA mixture.
Coolant	50/50 mix of water and antifreeze	Balanced coolant mixture of water, antifreeze and coolant additives			Drain and replace the mixture every 6 months or after 500 hours of operation. Do not add cold coolant to a hot engine; allow engine to cool below 120 F (50 C) before adding coolant.
Coolant	Water/antifreeze mixture				Permanent type antifreeze mixed per supplier for lowest expected ambient; do not use anti-leak additives
Engine oil		Refer to Cummins engine Operation and Maintenance Manual for lubricating oil classification			Gensets are shipped with oil added.
Engine oil	5W (Synthetic Oil)	API CC/CD, sulphated ash max 1.85%	below -23°C		Below -10 F (-23 C) and below; pour point 9 F (5 C) below lowest expected temperature
Engine oil	10W-30	API CC/CD	-23°C to -10°C		-10 F (-23 C) to 14 F (-10 C)
Engine oil	15W-40	API CC/CD	above -10°C		14 F (-10 C) and above
Engine oil	20W-40	API CC/CD	above 0°C		32 F (0 C) and above
Fuel	Diesel				Do not use zinc coated or copper fuel lines with diesel fuel.
Fuel	No. 2 diesel				Direct injection fuel system; fuel filter; water separator; automatic electric fuel shutoff.
Fuel	diesel				Do not use zinc coated or copper fuel lines with diesel fuel.
Hydraulic oil	DOT-3				Trailer master cylinder reservoir - keep at least half full
Other	Starting battery electrolyte specific gravity			1.26 specific gravity	1.225 specific gravity recommended where ambient temperature is consistently above 95 F (35 C) to reduce electrolyte loss

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Fault codes

Code	Name	Meaning	Severity	Action
101	IDLE MODE	Indicates that the engine is operating in idle mode. Grounding the engine idle input inhibits generator build-up and governs the engine at 800 RPM; control lowers oil pressure warning and shutdown trip points accordingly.	Warning	None required; removing ground returns the genset to normal speed and voltage.
102	EMERGENCY STOP	Indicates local or remote Emergency Stop.	Shutdown	Pull the button out (turn clockwise to allow it to pop out); move Run/Off/Auto switch to Off; press the Reset switch; select Run or Auto as required. Reset only at the PCC front panel.
121	SPEED SIGNAL LOST	Mag pickup speed indication is not being sensed.	Shutdown	Restart and check RPM on digital display; inspect MPU wires/connector pins; check for 3.5 to 15 VAC at MPU while cranking.
135	OIL PRESSURE SENSOR H	Engine oil pressure sender signal is shorted high.	Warning	Check sender/connectors/wires; verify fault simulation not enabled; check 0.5 to 4.5 VDC at P7-13 (OP OUT) and P7-17 (OP COM).
141	OIL PRESSURE SENSOR L	Engine oil pressure sender signal is shorted low.	Warning	Check sender/connectors/wires; check for shorts/open circuits at P7-13, 17, 21.
143	PRE-LOW OIL PRES	Engine oil pressure dropped to an unacceptable level.	Warning	Check oil level, lines and filters; replenish if low; if powering critical loads wait until next shutdown period and follow code 415.
144	COOL SENSOR HIGH	Engine coolant temperature signal is shorted high.	Warning	Check sender/connectors/wires; check resistance between P7-30 (IH20) and P7-34 (IH20 COM).
145	COOL SENSOR LOW	Engine coolant temperature signal is shorted low.	Warning	Check sender/connectors/wires; check for shorts at P7-30 and P7-34.
146	PRE-HIGH COOL TMP	Engine has begun to overheat (coolant temperature risen to an unacceptable level).	Warning	Reduce load; check air inlets/outlets and remove obstructions to airflow; if engine can be stopped follow code 151.
151	HIGH COOLANT TEMP	Engine has overheated (coolant temperature above the shutdown trip point).	Shutdown	Allow engine to cool; check coolant level; check airflow obstructions; check fan belt; check blower fan/remote radiator pumps; reset control and restart.
197	LOW COOLANT LEVEL	Engine coolant level has fallen below the warning trip point.	Warning	Allow engine to cool; check coolant level and replenish; look for leaks; reset control and restart.
200	LOW OIL PRESSURE	Indicates engine oil pressure has dropped to an unacceptable level.	Warning	If powering critical loads and cannot be shut down, wait until next shutdown period then follow the 201-SHUTDOWN procedure. Check oil pressure via the Oil Pressure menu prior to clearing the fault.
201	LOW OIL PRESSURE	Indicates engine oil pressure has dropped below the shutdown trip point.	Shutdown	Check oil level, lines and filters; if oil system is OK but oil level is low, replenish; reset control and restart. Oil pressure limits are listed in Table 4-3.
204	OIL PRES SENDER	Indicates that the control has sensed that the engine oil pressure sender is out of its working range.	Warning	Check that the engine oil pressure sender is properly connected.
210	LOW COOLANT TEMP	Warning occurs when engine coolant temperature is 70 deg F (21 deg C) or lower while set is not operating.	Warning	Indicates engine coolant heater is not operating or is not circulating coolant; check coolant heater power supply/fuse, low coolant level, and open heater element.
211	HIGH COOLANT TEMP	Indicates engine coolant temperature is getting close to the recommended maximum (215 deg F/102 deg C standby or 207 deg F/97 deg C prime).	Warning	Reduce load if possible; check air inlets and outlets and remove obstructions to airflow; if engine can be stopped follow the 212-SHUTDOWN procedure.
212	HIGH COOLANT TEMP	Indicates engine has overheated (coolant above 223 deg F/106 deg C standby or 215 deg F/102 deg C prime).	Shutdown	Allow engine to cool; check for obstructions to cooling airflow, check fan belt, check coolant mixture, check blower fan and circulation pumps; reset control and restart after correcting problem.
213	COOLANT SENDER	Indicates that the resistance of the coolant temperature sender is out of range.	Warning	Check the resistance of the sender (should be 500 to 2k ohms).
214	LOW COOLANT LVL	Indicates engine coolant level has fallen below the trip point.	Warning	Allow engine to cool; check coolant level in radiator and recovery bottle and replenish if low; check for possible coolant leakage points.
215	LOW COOLANT LVL	Indicates engine coolant level has fallen below the shutdown trip point.	Shutdown	Check coolant level in radiator and recovery bottle and replenish if low; check defective coolant bottle hose or radiator cap; reset control and restart after correcting problem. Will not occur in Idle mode.
220	MAG PICKUP	Indicates mag pickup speed indication is not being sensed or does not match generator set output frequency.	Shutdown	Restart and check RPM on the digital display; isolate per troubleshooting table 4-18.
221	FAIL TO CRANK	Indicates possible fault with control or starting system.	Shutdown	Check fuse F3 on the Engine Interface board; clean battery cable connections; recharge or replace battery.
222	OVERCRANK	Indicates possible fuel system problem.	Shutdown	Check for empty fuel tank, fuel leaks, or plugged fuel lines; check for dirty fuel filter and replace; check for dirty or plugged air filter and replace; reset control and restart.
223	OVERSPEED	Indicates engine has exceeded normal operating speed (115% +/-1% of nominal).	Shutdown	Inspect mechanical fuel linkage; check EFC for binding/damage; monitor PCC duty cycle and replace A32 or A38 as indicated.
224	FAIL TO SYNCHRONIZE	The generator set has not synchronized to the system bus within the allowable time frame.		Check governor system stability and adjust governing/synchronizer parameters; check for fuel system problems causing engine instability; widen synchronizing window and reduce acceptance time delay.
226	FAIL TO CLOSE	Indicates that the paralleling breaker has been given a signal to close, but has not closed properly.		Verify charging mechanism of paralleling breaker; check the close signal to the breaker; verify auxiliary contact signals from the breaker to the control are operational.
230	LOW DC VOLTAGE	Indicates battery voltage is below 10 VDC.	Warning	Check battery charger fuse and recharge or replace battery; clean and tighten battery cable connections; check engine DC alternator; check battery charge voltage float level.
231	HIGH DC VOLTAGE	Indicates battery voltage exceeds 32 VDC.	Warning	Check voltage float level on battery charger (lower float level); check engine DC alternator and replace if normal charging voltage is not obtained.
232	WEAK BATTERY	Indicates battery voltage drops below 60% of nominal for two seconds during starting.	Warning	Discharged or defective battery; see warning message 230, LOW DC VOLTAGE.
234	OVERSPEED	Engine has exceeded normal operating speed.	Shutdown	Clear fault and restart genset; check fault threshold; monitor RPM; check electronic governor actuator.
235	LOW COOLANT LEVEL	Engine coolant level has fallen below the shutdown trip point.	Shutdown	Check coolant level and replenish; look for leaks; reset control and restart.
240	LOW FUEL-DAY	Indicates day tank fuel supply is running low.	Warning	Check fuel supply and replenish as required.
241	LOW FUEL	Indicates fuel supply is running low.	Warning	Check fuel supply and replenish as required.
250	EEPROM ERROR	Indicates PCC memory error - data corruption of critical operating parameters.	Shutdown	Perform initial start setup; turn Run/Off/Auto to Off and reset; if the same EEPROM ERROR message occurs, replace the digital board (A32).
251	EEPROM ERROR	Indicates PCC memory error - data corruption of noncritical operating parameters.	Warning	Perform adjustment procedures and save; if the same EEPROM ERROR message occurs, replace the digital board (A32).
252	EEPROM ERROR	Indicates PCC memory error - data corruption of noncritical operating parameters.	Warning	Verify values/choices selected and repeat the save operation; if the same EEPROM ERROR message occurs, replace the digital board (A32).
260	CUSTOMER FAULT 1	Customer defined input closed to ground; message is editable.		Isolate the source of the false signal; check A34 LED corresponding to the fault input.
261	GROUND FAULT	Customer defined input closed to ground (default message); message is editable.		Isolate the source of the false signal; check A34 LED corresponding to the fault input.
262	RUPTURE BASIN (DAY TANK)	Customer defined input closed to ground; message is editable.		Isolate the source of the false signal; check A34 LED corresponding to the fault input.
263	HIGH GEN TEMP	Customer defined input closed to ground (default message); message is editable.		Isolate the source of the false signal; check A34 LED corresponding to the fault input.
270	PHASE ROTATION	The phase relationship between the generator set and the system bus is not matched.	Shutdown	Using a phase rotation checker, verify that the generator set phase rotation matches the system bus; verify control wiring to the bus PT module is properly connected.
272	FIRST START	The PowerCommand control is not receiving a proper signal from the system master first start sensor.	Warning	Control reverts to fallback mode; verify the Master First Start Sensor is functioning and that the voltage pulse is present at the PowerCommand control (terminal TB1-50); check interconnection wiring.
301	HIGH AC VOLTAGE	Indicates that one or more phase voltages has exceeded 130% of nominal, or exceeded 110% of nominal for 10 seconds.	Shutdown	Isolate the regulator module (A37), engine interface board (A31), digital board (A32), PMG/field wiring or PT/CT sensing path per troubleshooting table 4-29.
303	LOW AC VOLTAGE	Indicates that one or more phase voltages has dropped below 85% of nominal for 10 seconds.	Shutdown	Check PMG or field wiring, rotating rectifier diodes, overload, loose connectors, and voltage sensing circuitry per troubleshooting table 4-30.
313	UNDER FREQUENCY	Indicates that engine speed has dropped below 90% of nominal for 10 seconds. (Five seconds before shutdown, a Load Dump signal is initiated.)	Shutdown	Check fuel supply, intake air supply and load; check Initial Setup (set size).
320	OVERCURRENT	Indicates that generator output current has exceeded 110% of rated for 60 seconds.	Warning	Check load and load lead connections.
321	OVERCURRENT	Indicates that generator output current has exceeded 110% of rated, and a PCC time/current calculation has initiated an overcurrent shutdown.	Shutdown	Check load and load lead connections.
322	SHORT CIRCUIT	Indicates that generator output current has exceeded 175% of rated.	Shutdown	Check load and load lead connections.
330	OVERLOAD	Indicates that three-phase power output exceeds 105% of standby (or 115% of prime) rating.	Warning	Check load and load lead connections.
335	REVERSE POWER	Indicates that power is flowing into the generator set rather than out from the unit.	Shutdown	Verify connection of generator set CT's; verify proper connection of load sharing lines; verify correct frequency and voltage on all sets.
337	LOSS OF EXCITATION	Indicates that the alternator excitation system is improperly adjusted or has failed.	Shutdown	Check output voltage with calibrated meter and adjust; check load sharing lines; see Section 6 Servicing the Generator.
359	FAIL TO START	Engine cranks but fails to start (possible fuel system problem).	Shutdown	Check for empty fuel tank, fuel leaks, or plugged fuel lines; replace dirty fuel filter; replace dirty air filter; reset control and restart.
415	LOW OIL PRESSURE	Engine oil pressure has dropped below the shutdown trip point.	Shutdown	Check oil level, lines and filters; replenish if low; reset control and restart.
421	OIL TEMP	Engine has begun to overheat (oil temperature above unacceptable level) (Optional).	Warning	Reduce load; check air inlets/outlets; if engine can be stopped follow code 151 and check engine oil level.
441	LOW BAT VOLTAGE	Battery voltage supply to the control approaching a low level.	Warning	Check battery charger fuse; recharge or replace battery; clean and tighten cable connections; check engine DC alternator.
442	HIGH BAT VOLTAGE	Battery voltage supply approaching a high level at which control damage can occur.	Warning	Check float level on battery charger; check battery wiring/calibration.
1122	Rated/Idle Trans		Info
1123	SHUTDOWN AFTER BS	A shutdown fault occurred while Battle Short was enabled and transitioned from enabled to disabled.	Shutdown	Review Fault History and perform corrective action.
1124	DELAYED SHUTDOWN	A shutdown fault became active while the Delayed Shutdown feature was enabled.	Warning	Review Fault History and perform corrective action.
1131	BATTLE SHORT ACTIVE	Control is in Battle Short mode (bypasses several critical fault shutdowns).	Warning	None; used for genset operation during emergencies.
1311	Customer Input #1			Nature of fault is optional customer selection. Example inputs: Low Fuel Day Tank, Water In Fuel, Ground Fault, Low Starting Hydraulic Pressure, Low Starting Air Pressure, etc. Programmable via service tool.
1311, 1312, 1317, 1318	CUSTOMER INPUT #1 - #4	Optional customer-selected fault input is active.		Disconnect signal lead from TB1 and reset the control; check external wiring/active input selection.
1312	Customer Input #2			Nature of fault is optional customer selection. Example inputs: Low Fuel Day Tank, Water In Fuel, Ground Fault, Low Starting Hydraulic Pressure, Low Starting Air Pressure, etc. Programmable via service tool.
1317	Customer Input #3			Nature of fault is optional customer selection. Example inputs: Low Fuel Day Tank, Water In Fuel, Ground Fault, Low Starting Hydraulic Pressure, Low Starting Air Pressure, etc. Programmable via service tool.
1318	Customer Input #4			Nature of fault is optional customer selection. Example inputs: Low Fuel Day Tank, Water In Fuel, Ground Fault, Low Starting Hydraulic Pressure, Low Starting Air Pressure, etc. Programmable via service tool.
1334	CRIT SCALER OR	Incorrect feature or calibration was entered into control.	Shutdown	Reload correct feature/calibration file.
1335	NONCRIT SCALER OR	Incorrect feature or calibration was entered into control.	Warning	Reload correct feature/calibration file.
1337	No Message		Info
1416	FAIL TO SHUTDOWN	Genset continues to run after receiving shutdown command (Battle Short feature enabled).	Warning	Check Battle Short feature setting.
1417	POWER DOWN ERROR	Controller cannot power down because of an unknown condition.	Warning	Check for possible battery drain.
1433	EMERGENCY STOP	Local Emergency Stop.	Shutdown	Pull the button out; move switch to O; press Fault Acknowledge/Reset; select Manual or Auto.
1434	REMOTE E-STOP	Remote Emergency Stop.	Shutdown	See code 1433 to reset.
1435	LOW COOLANT TEMP	Engine coolant heater is not operating or not circulating coolant (coolant <=70 F [21 C]).	Warning	Check coolant heater power/fuse/cord; check coolant level; check heater element (10 to 60 ohms); check sensor.
1438	FAIL TO CRANK	Engine failed to crank after the PCC received a start signal.	Shutdown	Test for B+ at the starter; check fuse F3 (2 Amps); check K4 start pilot relay and starter circuitry; refer to code 121.
1442	WEAK BATTERY	During cranking battery voltage at or below weak battery trip point.	Warning	Recharge or replace battery; check electrolyte level and connections; check harness.
1443	BATTERY FAILED	Dead battery - engine will not start.	Shutdown	See code 1438 instructions.
1444	KW OVERLOAD	Generator output power exceeded 105% of genset rating (3 sec at 110% of rated).	Warning	Check load and load lead connections; check CTs and CT connections.
1445	SHORT CIRCUIT	Generator output current exceeded 175% of rated.	Shutdown	Check load and load lead connections (fault may not reset for several minutes).
1446	HIGH AC VOLTAGE	Phase voltage exceeded 130% of nominal, or 110% of nominal for 10 seconds.	Shutdown	Check fault simulation; clear fault and restart; refer to Generator/Base Board Isolation Procedure.
1447	LOW AC VOLTAGE	Phase voltage dropped below 85% of nominal for 10 seconds.	Shutdown	Check load; reconnect per reconnection diagram; check PMG/field wiring; check P8-21/P8-22 shunt connections.

Showing the first 80 of 145 codes.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Procedures

Adjusting Values/Parameters adjustment

⚠ If Home button or Previous Main Menu button is pressed before pressing save symbol, changes are not saved.

Press button next to symbol in display until + and − symbols are displayed.
Press button next to arrow symbols to move to numeric character to change.
Press button next to + symbol to increase value or select parameter.
Press button next to − symbol to decrease value or select parameter.
After adjusting values/selecting parameters, press symbol to save changes.

Convert Day Tank Controller 240 VAC to 120 VAC adjustment

Remove the two jumpers between terminals TB1-6 and TB1-7.
Connect one jumper between TB1-5 and TB1-6 and the other between TB1-7 and TB1-8.
Move selector switch S103 on the control PCB to the up position for 120V.
If equipped with a transformer, remove jumpers between H2 and H3 and connect one between H1 and H3 and the other between H2 and H4.

Day Tank Controller Conversion 240 VAC to 120 VAC adjustment

Remove the two jumpers between terminals TB1-6 and TB1-7 and connect one between TB1-5 and TB1-6 and the other between TB1-7 and TB1-8.
Move selector switch S103 on the control PCB to the up position for 120V.
On the control transformer, remove the two jumpers between terminals H2 and H3 and connect one between H1 and H3 and the other between H2 and H4.

Dip Adjustment adjustment

Turn the DIP pot clockwise to increase the voltage vs frequency slope for frequencies below the UFRO threshold.
Greater slope gives greater voltage roll off as frequency drops, easing large load pickup but increasing voltage dip.
Turn the pot fully counterclockwise to make the slope the same above and below the threshold frequency.

Dwell Adjustment adjustment

Turn the DWELL pot clockwise to increase dwell time (voltage recovery time when frequency dips below threshold).
Turn the DWELL pot fully counterclockwise to eliminate dwell.
With no dwell, voltage recovery follows engine speed recovery.

Electric Governor Calibration Checks adjustment

Tools: Frequency meter or tachometer

Start the generator set.
Set no-load speed for desired droop (isochronous 60.0 Hz/1800 r/min).
With no load, turn GAIN clockwise until actuator lever oscillates; reduce until stable.
Reduce GAIN one division, then turn fully clockwise while observing lever.
Turn I adjustment counterclockwise until lever stable; it should oscillate up to 3 times.
Apply and remove loads to check response; recalibrate if unsatisfactory.

Electric Governor Controller Adjustments adjustment

⚠ If adjustment must be made while the unit is running, use extreme caution around hot manifolds and moving parts

Tools: Frequency meter

Move RUN/STOP/REMOTE switch to RUN and operate set at no load.
Confirm DROOP potentiometer adjust is set at zero position.
Set speed by adjusting the SPEED potentiometer to 50 or 60 Hz.
Adjust GAIN potentiometer clockwise until engine starts to hunt, then counterclockwise until speed is stable.
Adjust the 'B' potentiometer the same as GAIN.
Adjust the 'I' potentiometer to decrease overshoot above rated speed.
Apply 1/4 load and adjust the GAIN potentiometer again.
Apply full load to be certain the set will carry it; lengthen actuator linkage if it will not.

Electric Governor Preliminary Adjustments adjustment

Tools: Screwdriver

Set frequency adjust (engine speed) potentiometer to mid position and tighten locking nut.
Set I potentiometer one division from zero.
Set Gain potentiometer at the third division from zero.
For isochronous operation turn Droop potentiometer fully counterclockwise.
Turn droop screw to approximately 40 for 3 percent droop.
Turn droop screw to approximately 80 for 5 percent droop.

Fuel Pump Control: Convert 120 VAC to 240 VAC adjustment

Remove jumpers between TB1-5/TB1-6 and TB1-7/TB1-8; connect two jumpers between TB1-6 and TB1-7.
Move selector switch S103 on control PCB to down position for 240 VAC.
If equipped with a transformer, remove jumpers between H1/H3 and H2/H4 and connect two jumpers between H2 and H3.
Attach a tag to the control box indicating the supply voltage.

Fuel Pump Control: Convert 240 VAC to 120 VAC adjustment

Remove jumpers between TB1-6/TB1-7; connect one jumper TB1-5 to TB1-6 and one TB1-7 to TB1-8.
Move selector switch S103 on control PCB to up position for 120V.
If equipped with a transformer, remove jumpers between H2/H3 and connect one between H1-H3 and one between H2-H4.

Governor Adjustments (Type A Electric Governor) adjustment

Set selector switch S1 to OFF, S2 to appropriate model position.
Set pots initially: Gain 20%, I 20%, D 30%, Droop 0%.
Start set, adjust Speed pot for required frequency (60Hz=1800RPM or 50Hz=1500RPM) at operating temperature.
Disconnect load, turn Gain pot to 100% or until unstable, then back off until stable.
Adjust D and I pots similarly; readjust Speed if necessary.
Push throttle to minimum speed, release and observe overshoot (2-5 Hz acceptable); adjust I pot to reduce overshoot or hunting.

Initial Start Setup adjustment

⚠ Selecting this menu resets all operating parameters to default values; perform only by technically qualified personnel.

Press RESET, MENU and PHASE SELECT simultaneously to invoke the Initial Start Setup menu.
Toggle the Standby/Prime option.
Select the correct generator set model, frequency and kW rating.
Select the correct nominal line-to-line output voltage.
Select DELTA or WYE.
Select SAVE to save changes; MAIN MENU is then displayed.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Voltage reconnection

Voltage	Phase	Connection	Leads	Notes
		AVR response jumper	A to C	For generator output 90 kW or less (SX440 and MX321)
		Auxiliary terminal board TB21	K1, K2, P2, P3, P4, S2, S1, A2, A1	A1 and A2 connect a VAR/power factor controller when paralleling with a utility; S1 and S2 connect a droop compensating CT when paralleling with a generator set or utility
		CT1 - U load leads (A phase); CT2 - V load leads (B phase); CT3 - W load leads (C phase)	6 lead gensets: generator output leads routed through CTs; 12 lead gensets: load wires routed through CTs	12-lead sets have dual secondary CTs (3 pins); 6-lead sets have single secondary CTs (2 pins)
		Day tank LO SHUTDOWN engine shutdown connection	TB1-14 to engine block ground; TB1-15 to TB2-16 on the ECM
		Fault relay K8/K9 (Dry Contact Module)	K8=Over Crank, Low Oil Pressure, High Engine Temperature, Low Coolant Level, Low Fuel Level; K9=Low Fuel Level, Rupture Basin	Contact ratings: 40A max carry/break N.O. 12V coil, 30A N.C. 12V coil, 20A N.O./10A N.C. 24V coil
		MX321 PMG-excited jumper positions	2-3, 4-5 and 6-7	These jumpers must be in these positions
		MX321 voltage regulator frequency jumper	3-2 for 50 Hz; 3-1 for 60 Hz
		SX440 voltage regulator frequency jumper	C-50 for 50 Hz; C-60 for 60 Hz
		TB3 (ECM alternative RUN/STOP/REMOTE connection)	TB3-1=REMOTE, TB3-2=RUN, TB3-3=STOP	Provides alternative direct connection to ECM for troubleshooting or customer connection
		Voltage trimmer R21	voltage regulator terminals 1 and 2	There must be a jumper between terminals 1 and 2 when voltage trimmer R21 is not used
	single phase	QSG-Series power distribution panel voltage selector switch S1 position	main output terminals	Rotary switch under lockable cover selects 120/240 VAC single phase
	single phase	Voltage regulator terminal 6	jumpered to terminal 8	When the generator is connected for single-phase output, terminal 6 is not connected to the isolation transformer
	three phase	QSG-Series power distribution panel voltage selector switch S1 position	main output terminals	Rotary switch selects 120/208 VAC three phase
110/190	3
110/220	1
110V - 120V L-N	Single phase, 2-wire	Jumper locations for single phase, 2-wire		PTC Module AC wiring (0300-5382-01, -02)
115/220	3
115/230	1			Generator voltage connections (reconnectable type only) per Figure 5-20; single phase double delta connection will reduce set rating and may not work with 3-phase meters
120	single phase	Day tank fuel pump control power reconnection	move jumpers from TB1-6/TB1-7 to TB1-5/TB1-6 and TB1-7/TB1-8	Move selector switch S103 on the control PCB to the up position for 120 V (factory set for 240 V, S103 down)
120/208	3
120/240	1
127/220	3
139/240	3
190, 200, 208, 220, 230, 240, 380, 416, 440, 460, 600 (L-L)	3 (three phase)	3 or 4 wires		Voltage Configuration submenu; default = 3Ph 208V 4W
190V - 240V L-L	Three phase	Jumper locations for three phase, 190V-240V L-L		Use 0300-5382-01 for 190V-240V L-L, 50/60 Hz
200, 220, 230, 240 (L-L)	1 (single phase)	3 wires		Voltage Configuration submenu (Governor/Regulator Setup)
200V - 240V L-L	Single phase, 3-wire	Jumper locations for single phase, 3-wire		PTC Module AC wiring
220/380	3
220/480	3
230/400	3

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

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

149

Part #	Description	Category
982-0200	Air Filter	Air filter
309-0272	Regulator, Voltage - 24 VDC (Used on 35 A MP Alternator)	Alternator
309-0561	Alternator & Drive Components Group Pulley. Alternator - Multi Groove (Use with 35 A MP Alternator)	Alternator
AN500T0083	ALTERNATOR	Alternator
150-2007	Guard. Belt Screw. Cap - Hex Head (1/2-13 X 2-1/4“)	Belt
187-0008	Belt, Drive	Belt
187-0009	Belt, Drive	Belt
328876800	Belt, V-Grooved	Belt
FP-3034946	Multi-Groove Fan Belts (Ribbed 8) (62.5" X 1.125")	Belt
FP-3911558	Belt, V Ribbed (Alternator)	Belt
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
DM-3801371	Gasket Set - 4BT 3.9	Gasket
FP-3901356	Turbo Charger Mounting Gasket	Gasket
FP-3905443	Gasket, Exhaust Manifold	Gasket
FP-3911535	Gasket, Oil Pan	Gasket
FP-3926760	Gasket, Oil Cooler Core	Gasket
FP-3928493	Gasket, Rear Cover	Gasket
FP-3929792	Gasket, Filter Head	Gasket
FP-3937706	Turbocharger Oil Drain Gasket (H x 35)	Gasket
FP-3938157	Gasket, Pick-Up Tube	Gasket
FP-3938158	Gasket, Air Intake Connection	Gasket
FP-3939258	Gasket, Fuel Transfer Pump Mounting	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
501-0441	Line, Fuel - Flex (Fuel In)	Hose
501-0502	Line, Fuel-Flex (Fuel Out)	Hose
503-0098	Hose, Oil Drain - Bulk (Order By The Foot - 3 Feet Required)	Hose
503-0183	Clamp, Hose	Hose
503-0197	Clip, Hose	Hose
503-0685	Clamp, Hose	Hose
DM-3805455	Oil Cooler Hose - 4BT 3.9	Hose
3822509	Injection Pump Bore Brush Service Tool	Injector
3823276	injector bore brush	Injector
DM-3029550	Fuel Injector - 4BT 3.9	Injector
0332-3925-02	Jumper-Terminal	Jumper terminal
0332-3943-02	Jumper-Terminal	Jumper terminal
REC149-2106	By-pass filter I	Oil filter
REC1491754	By-pass filter II	Oil filter
0249-0814	Relay 2P Base	Service part / kit
0332-3926	Terminal Block (End Stop)	Service part / kit
0332-3927-02	Terminal Block (End Plate)	Service part / kit
102-1237	Adapter, Drain-Oil	Service part / kit
151-0611	Control, Governor	Service part / kit
155-2175	Clamp, Muffler 4"	Service part / kit
187-0007	INJ	Service part / kit
187-0012	Filter, Fuel	Service part / kit
187-0015	Filter, Oil	Service part / kit
201-3434-01	Diode, Positive (Forward) Includes Lead	Service part / kit
201-3434-02	Diode, Negative (Reverse) Includes Lead	Service part / kit
300-2810	Board - Engine Monitor (All) (Includes Fuses)	Service part / kit
305-0823	# Model MX321	Service part / kit
309-0553	Switch, Temperature-Pre Water	Service part / kit
309-0554	SWITCH WATER	Service part / kit
323-1200	# Socket, Contact (Used in J1, J2)	Service part / kit
323-1304	tiotming, Umector	Service part / kit
323-1306	Genset component (SJB series)	Service part / kit
332-0051	Clamp, Loop	Service part / kit
332-0941	*Tie, Cable	Service part / kit
332-1279	Terminal. Lug - Ring (3/8	Service part / kit
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	Service part / kit
332-2739	Bracket	Service part / kit
332-2921	Switch, Temperature - Washer, Lock (M8)	Service part / kit
3377259	bosch timing tool (ve)	Service part / kit
357-0030	Rectifier	Service part / kit
416-0446	Cable, Battery - Jumper	Service part / kit
504-0011	Valve, Shutoff (1/2”)	Service part / kit
505-0026	Coupling, Pipe (1/8")	Service part / kit
505-0050	Elbow, Street (1/2' x 90 ° )	Service part / kit
505-0098	Band	Service part / kit
505-0104	Nipple, Pipe - Close	Service part / kit
505-0185	Nipple, Half (1/2' x 1.5' lg)	Service part / kit
526-0008	148-036’?	Service part / kit
526-0018	Gasket, Flange (1-3/4)	Service part / kit
526-0115	Washer (5/16 “)	Service part / kit
526-0196	Washer, Spacer - Shield JC)INT, BALL LINKAGE	Service part / kit
526-0327	Control, Governor	Service part / kit
800-0012	Screw, Cap - Hex Head (1/4-20 x 2-1/4”) Begin Spec C MANIFOLD KIT, INTAKE	Service part / kit
800-2060	Screw, Cap - Hex Head (M8x 1.25 x35)	Service part / kit
800-2110	Hood, Inlet - Air Molded	Service part / kit
800-2112	Screw. Cap - Hex Head (M12 x 30nin)	Service part / kit
812-0075	Screw-RHM(8-32xl/4)	Service part / kit
813-0103	Screw, Machine - Round Head (#10-32 x 3/4º)	Service part / kit
815-0172	Cover, Adapter Outlet	Service part / kit
850-0025	Screw, Machine - Round Head (#8-32 x 3/8" )	Service part / kit
850-0030	Washer, Lock - Spring (#10)	Service part / kit
850-0050	Washer, Lock - Spring (3/8”)	Service part / kit
850-2006	Washer, Lock - Spring (M6)	Service part / kit
850-2008	Washer, Lock (M8)	Service part / kit
850-2012	Washer, Lock - Spring (M12)	Service part / kit
856-0013	Washer, Lock - W/EIT (1/2)	Service part / kit
860-2007	Circuit Breaker Used With Westinghouse Circuit Breaker	Service part / kit
870-0053	Nut, Hex (s10-32)	Service part / kit
870-0131	Nut. Hex - with ET (#10-32)	Service part / kit
870-0212	Nut, Locking (1/4-20)	Service part / kit
871-0010	Nut, Hex - Srass (#10-32) Washer, Lock - EIT (#10) Washer, Lock - IT (#10)	Service part / kit
871-0028	NUT	Service part / kit
960-0136	Battery, 24V, 55Ah, AGM	Service part / kit
965-0520	Cooling Fan	Service part / kit
DM-3802010	Main Bearing Set Standard - 4BT 3.9, 6BT 5.9, 6CT 8.3	Service part / kit
FP-3903575	Kit, Solenoid 12 Volt	Service part / kit
FP-3903576	Kit, Solenoid 24 Volt	Service part / kit
FP-3910739	Bearing, Ball (Fan Drive)	Service part / kit
FP-3918428	Plunger, Pressure Regulator	Service part / kit
FP-3957543	Element, Oil Cooler	Service part / kit
187-0001	Pump, Water	Pump
187-0013	Pump, Transfer-Fuel	Pump
187-0018	INJ. PUMP	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
FP-3286277	Water Pump	Pump
FP-3928143	Pump, Fuel Transfer	Pump
FP-3970880	Pump, Fuel Transfer	Pump
FP-4939585	Pump, Lubricating Oil	Pump
FP-4947710	Pump, Fuel Transfer	Pump
0307-3047	Relay (24V)	Relay 24v
509-0266-01	Ring, O	Seal
FP-3883284	Seal, O-Ring, Air Intake Connection	Seal
FP-3900808	Seal, Injector	Seal
FP-3903380	Seal, Banjo Connector (Fuel Manifold)	Seal
FP-3906659	Seal, Injector	Seal
FP-3906698	Seal, Rectangular Ring	Seal
FP-3909356	Seal, Injector	Seal
FP-3909397	Seal, O-Ring	Seal
FP-3909410	Seal, Rear Service Kit (Dry Clutch Housing)	Seal
FP-3913994	Seal, O-Ring	Seal
FP-3921640	Seal, Valve Stem (Intake & Exhaust) (For Engines Built Before April 2003)	Seal
FP-3931824	Seal, O-Ring, Turbo Oil Line	Seal
FP-3937111	Seal, Front Service Kit	Seal
FP-3957912	Seal, Valve Stem (For Engines Built After April 2003)	Seal
150-2201	Sensor, Speed – Magnetic	Sensor
193-0244	Sender, Oil Pressure (E1)	Sensor
193-0353	Sender, Temperature - Oil	Sensor
193-0375	Sender, Coolant	Sensor
309-0269	Sender, Temperature-Lo Engine	Sensor
505-0059	Sensor, Water Pressure	Sensor
M-1695	Oil temperature sender	Sensor
AN500T0013	STARTER MOTOR	Starter
0332-3923-02	Terminal Block	Terminal block
0332-4036-02	Terminal Block (Earth)	Terminal block
187-0020	Thermostat	Thermostat
DM-3015282	Thermostat 180F - 4BT 3.9, 6BT 5.9	Thermostat
FP-3802273	Kit, Thermostat (83° C), (181° F)	Thermostat
FP-3917324	Assembly, Thermostat (83° C), (181° F)	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 oil capacity of the Cummins/Onan 4BT3.9?

The Cummins/Onan 4BT3.9 engine has an oil capacity of 11.0 liters.

What is the displacement of the Cummins/Onan 4BT3.9?

The Cummins/Onan 4BT3.9 has a displacement of 3.9 liters with 4 cylinders.

Which generators use the Cummins/Onan 4BT3.9 engine?

The Cummins/Onan 4BT3.9 powers 2 generator set(s), including Cummins/Onan DGCA, Cummins/Onan DGCB.

What is a common problem with the Cummins/Onan 4BT3.9 engine?

A commonly reported issue on generators using the Cummins/Onan 4BT3.9 is: Engine cranks but will not start. Cause: Empty fuel tank, fuel leaks, or plugged fuel lines. Fix: Correct as required.