Home›Engines›Cummins/Onan NT855-G

Cummins/Onan NT855-G Engine

The Cummins/Onan NT855-G is a 14 L 6-cylinder solenoid shift isochronous engine rated at 1800 rpm, producing up to 265 kW. It powers generator sets from Cummins/Onan, including the DFE 15R, DFE Series, DFP 17R and DFP 517. It holds 14 L (3.7 gal) of oil and 53 L (14.0 gal) of coolant.

Also known as: Cummins NT855-G

Part of the Cummins/Onan NT855 engine family — 12 variants share parts & fitment.

14.0 L

Displacement

Cylinders

1800 rpm

Rated speed

265 kW

Gross power

On this pageSpecs Generator sets Maintenance FAQ

Engine specifications

Oil capacity	14.0 L
Coolant capacity	53.0 L
Displacement	14.0 L
Cylinders	6
Aspiration	Solenoid Shift Isochronous
Rated speed	1800 rpm
Gross power	265 kW

Generator sets powered by this engine

Cummins/Onan DFE 15RCummins/Onan DFE SeriesCummins/Onan DFP 17R Cummins/Onan DFP 517

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

Common problems

High engine temperature shutdown
Cause: Coolant level
Fix: Check coolant level; replenish if necessary
Fault lamp lights and engine shuts down after running for a period
Cause: Oil level (engine will shut down if sensor is closed)
Fix: Check oil level
Low oil pressure shutdown
Cause: Oil level
Fix: Check oil level; replenish if necessary
Overspeed shutdown
Cause: Governor and throttle linkages not free to move; overspeed switch
Fix: Check governor and throttle linkages for freedom of movement; check overspeed switch
Overspeed light on, no shutdown
Fix: Disconnect wire at TB11-29; light on after reset: replace engine monitor board
Low oil pressure light ON. No shutdown
Fix: Disconnect wire at TB11-30; light ON after relay reset: replace engine monitor board
High engine temperature light ON. No shutdown
Fix: Disconnect wire at TB11-31; light ON after relay reset: replace engine monitor board
Fault lamp lights, no fault exists
Fix: To check a no-fault condition, disconnect leads from TB11 terminals 29, 30 and 31; if fault lamp lights with leads disconnected, replace engine monitor board; reconnect leads
Fault lamp lights immediately after engine starts
Cause: Overspeed condition as engine starts
Fix: Check for overspeed condition as engine starts
Engine stops cranking and fault lamp lights, after cranking approximately 75 seconds
Fix: See engine service manual for troubleshooting fuel system; after correcting problem, reset engine monitor relay by placing Run-Stop/Reset-Remote switch to Stop/Reset, then back to the required running position
Overcrank fault lamp lights and engine stops cranking after approximately 75 seconds
Fix: See engine service manual for troubleshooting fuel system; after correcting fault, reset engine monitor relay by placing Run-Stop/Reset-Remote switch to Stop/Reset position, depressing Reset button, then to the required running position
Engine runs, shuts down, cranks for 75 seconds, cranking cycle stops, overcrank light ON
Cause: Fuel supply
Fix: Check fuel supply
Engine runs, shuts down and cranks for 75 seconds. Cranking cycle stops; fault lamp lights
Fix: See engine service manual for troubleshooting fuel system; after correcting problem, reset engine monitor relay by placing Run-Stop/Reset-Remote switch to Stop/Reset, then back to the required running position
Overcrank fault lamp lights and engine stops cranking after approximately 75-seconds
Fix: See engine service manual for troubleshooting fuel system; After correcting fault, reset engine monitor relay by placing Run-Stop/Reset-Remote switch to Stop/Reset position, depressing Reset button, then to the required running position
Engine runs, shuts down, cranks for 75-seconds, cranking cycle stops, overcrank light ON
Fix: Check fuel supply

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan NT855-G.

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Air filter	Air Filter		—	500 hr
Fuel filter	Replace Fuel Filter		—	3000 hr
Oil filter	Replace Oil Filter Element		—	1000 hr
Battery	Battery		—	1000 hr
Belt	Belt		—	500 hr
Coolant	Coolant	53.0	—	1000 hr
Coolant filter	A shut off valve (see Figure 30) is installed in the inlet and outlet line to the coolant filter to be closed, for minimum coolant loss when the filter is removed. Refer to engine manufacturer's manual for coolant filter replacement information.		—
Oil	Engine Oil	40.0 gallons	—	500 hr
Spark plug	Spark Plug		—	500 hr

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

Parts cataloged across the Cummins/Onan NT855 family

143

Part #	Description	Category
140-2389	140-2391 1 140-2390 1 140-2392 1 140-2393 1 140-1548 1 140-1545 1 c 503-1575 186917 C	Air filter
140-2391	Element - Air Cleaner (Standard)	Air filter
8342-1	AIR FILTER	Air filter
CS-1382c	INLET AIR DAMPER	Air filter
ES-1214-2	FLOAT SWITCH	Air filter
191-1982	Pulley, Alternator	Alternator
191-1983-02	Alternator, 24 Volt Spec B-O (Prestolite)	Alternator
A956	2-12 VOLT BATTERIES	Battery
2110153	Bell, End - Alt, to Exciter	Bell
511-0092	Belt, Alternator	Belt
805-35	Bolt, Place - Generator Mtg. Support to End Bell	Bolt
1S0A713	Bracket, Overspeed Switch	Bracket
2348115	Bracket, Mtg. - Volt. Cont. Reactor	Bracket
234875	Bracket, Gate Reactor Mtg.	Bracket
319-2236	Bracket, Mounting	Bracket
234070	Rig Assy., Brush- Incl. Brushes, & Contact Point Band, Gen. - Front Portion(Narrow)	Brush
2I4AM	Brush	Brush
518-0548-58	Clamp, Hose	Clamp
2340116	Cover, Exciter	Cover
0300-4623-08	DFBF (600V)	Current transformer
0300-4623-23	DFBF BR (0-480V)	Current transformer
FS1803s	FUEL FILTERS	Fuel filter
FP-3019158	Gasket, Water Outlet	Gasket
FP-3020943	Gasket, Exhaust Manifold	Gasket
FP-KS12622A	NH/NT855 In-Frame Kit w/upper gasket set & oil pan gasket	Gasket
FP-KS12622C	NH/NT855 In-Frame Kit w/upper gasket set & oil pan gasket	Gasket
FP-KS12622C7	NH/NT855 In-Frame Kit w/upper gasket set & oil pan gasket	Gasket
FP-KS12622D	NH/NT855 In-Frame Kit w/upper gasket set & oil pan gasket	Gasket
M-4024945	Edge molded rubber head gaskets set	Gasket
232A1817	Generator	Generator
502-0827	Fitting, Hose – Barbed (1/2” ID Pipe to 3/4” ID Hose)	Hose
503-0189	Clamp, Hose	Hose
503-1634-01	Hose, Rubber (3/4” ID x 4”)	Hose
FP-3013591	Piston Cooling Nozzle	Injector
FP-3054058	Injector, New	Injector
FP-3054250	Injector, New	Injector
302P465	RESISTOR-STABILIZING	Meter
302P466	For 220/380-V, 3-Ph, 60-Cycle (Model H)	Meter
302P468	For 120/208-V,120/240-V, & 347/600-V 3PH. 50 Cy!. (825-Ohm, 75-Watt)	Meter
302P469	For 220/380-V, 3Ph. 50-Cycle	Meter
302P470	For 277/480-V, 3-Ph, 50-Cyclo (5-P!)	Meter
102-1335	Plug, Oil Drain	Service part / kit
130-3588	Cap, Radiator	Service part / kit
130-4355	Radiator (2 Row Core) DFBJ	Service part / kit
130-4355-01	Radiator (3 Row Core) DFCF, DFCG	Service part / kit
130-4369	Radiator DFCH	Service part / kit
155-2409-01	Elbow, Exhaust (5" OD With Threads)	Service part / kit
191-1981	Genset component (SJB series)	Service part / kit
191-2121	Regulator, Voltage	Service part / kit
232A1489	Generator support shim, 0.598 in gauge #6, 3x3	Service part / kit
232A1490	Generator support shim, 0.359 in gauge #20, 3x3	Service part / kit
301021151	Box Only, control	Service part / kit
30118301	Bracket, Cont.Box Mtg. (Repl. 2-Piece Brkts)	Service part / kit
301A1914	Bracket, Panel Stop	Service part / kit
301A2727	Handle , Control Box	Service part / kit
302-213	60-Cycle	Service part / kit
302-234	.Cycle	Service part / kit
3028448	Plate, Mater Face	Service part / kit
302P411	302P412	Service part / kit
302P412	Scale Reads 0-250	Service part / kit
302P414	Amm, Scale Reads 0-300 - Replaces 302-14.	Service part / kit
302P415	Ammeter Scale Reads 0-500 - Replaces 302-371.	Service part / kit
302P422	302P423	Service part / kit
302P423	Scale Reads 0-750 on side of Gen	Service part / kit
302P467	For 277/480 Volt,3 Phase, 60 Cycle Plants.	Service part / kit
303-111	Rheostat, Volt. Reg. - 175-Ohm, (Model H)	Service part / kit
303-32	Knob, Rheos	Service part / kit
3040305	45, 000-Ohm, 10-W - For 480-V , 3-Ph, 3-Wire & 277/480-V, 3+ Ph.	Service part / kit
307-2621-02	Relay, Start Solenoid (K4)	Service part / kit
308-22	Switch, Volt. & Current Selector Ammeter	Service part / kit
32082	3-Phase Models	Service part / kit
320B18	Single Phase Models	Service part / kit
333-0639-01	Heater, Coolant (4990 Watt)	Service part / kit
333-0639-02	Heater, Coolant (6420 Watt)	Service part / kit
337A44	Strap, Ground	Service part / kit
402-78	Rubber, Mtg. - Cont. Box	Service part / kit
503-1575	Clamp, V-Band	Service part / kit
504-0011	Valve, Shutoff (1/2”)	Service part / kit
505-0019	Bushing, Pipe - Reducer 1/2” to 3/8”, DFBF (1/2” to 3/8”) 505-0131 DFCB, DFCC, DFCE (3/4” to 3/8”)	Service part / kit
505-0100	Nipple, Pipe - Close (1/2”)	Service part / kit
526-0029	*Washer, Flat (1/2")	Service part / kit
526-0219	Washer, Flat (1/2)	Service part / kit
800-0048	Screw, Cap - Hex Head (3/8-16 x 3/4”)	Service part / kit
800-0092	Screw, Cap - Hex Head (1/2-13 x 1.5)	Service part / kit
850-0050	Washer, Lock - Spring (3/8”)	Service part / kit
870-0212	Nut, Locking (1/4-20)	Service part / kit
903-0124	NA	Service part / kit
903-0204	NA	Service part / kit
903-0500	NA	Service part / kit
903-0604	NA	Service part / kit
EXS-1046s	CONDENSATION TRAP	Service part / kit
FP-855PREM	NH/NT855 Premium Cylinder Kits	Service part / kit
FP-855TT	NT855 Premium 3-Ring Cylinder Kits	Service part / kit
FP-855TTDN	NT855 Premium 3-Ring Cylinder Kits Dual-NI Pistons	Service part / kit
FP-855TTP	NT855 Premium Plus 3-Ring Cylinder Kits	Service part / kit
FP-855TTPDN	NT855 Premium Plus 3-Ring Cylinder Kits Dual-NI Pistons	Service part / kit
FP-IFK855NR	NT855 Cylinder Kits w/ no piston rings	Service part / kit
FP-IFK855PREM	NH/NT855 Premium Cylinder Kits	Service part / kit
FP-IFK855TT	NT855 Premium 3-Ring Cylinder Kits	Service part / kit
FP-IFK855TTDN	NT855 Premium 3-Ring Cylinder Kits Dual-NI Pistons	Service part / kit
FP-IFK855TTP	NT855 Premium Plus 3-Ring Cylinder Kits	Service part / kit
FP-IFK855TTPDN	NT855 Premium Plus 3-Ring Cylinder Kits Dual-NI Pistons	Service part / kit
FP-KS12621C	NH/NT855 Cylinder Kit Std Head Gask Grommets	Service part / kit
FP-KS12621C7	NH/NT855 Cylinder Kit .010 Head Gask Grommets	Service part / kit
FS1692s	FUEL SOLENOID VALVE LOCATION	Service part / kit
M-1808	DC CONTROL WIRING	Service part / kit
TB11-29	Engine Monitor Board	Service part / kit
TB11-30	Engine Monitor Board	Service part / kit
TB11-31	Engine Monitor Board	Service part / kit
234C134	3-Phase	Phase
234C137	3-Phase	Phase
234C140	Single Phase	Phase
234C141	Single Phase	Phase
FP-AR10172	Pump, Oil (New)	Pump
305P233	Rectifier, Lower Two, Neg. - Begin Spec B	Rectifier
305P234	Rectifier Assy., Power (Field) (Incl. in Rect. #305P218)	Rectifier
305P240	Rectifier, Volt. Cont.Reactor (Incl.in Rect. & Resistor A: 305P218)	Rectifier
3ISA78	Rectifier, Voltage Control	Rectifier
3044125	15,000-Ohm, 25-W - For 220/380-V, 3-Phase, 4-Wire	Resistor
304PA76	Resistor, Volt. Cont.Reactor (Incl.in Rect.& Resistor A: 305P218)	Resistor
3058227	Resistor Assy., Rect, & Incl. (Incl.in Rect. & Resistor A: 305P218)	Resistor
204493	Ring, Collector	Ring
508-0292	Washer, Sealing - Copper	Seal
DM-3010461	Crankshaft Rear Seal - NT855, NTC855	Seal
FP-3024709	Seal Ring, Water Manifold	Seal
193-0432	Sender, Oil Temperature (S2 Engine Block, E4 Oil Pan)	Sensor
193-0447-01	Sender, Water Temperature (E2)	Sensor
193-0448	Sender, Oil Pressure	Sensor
309-0269	Sender, Temperature-Lo Engine	Sensor
309-0576	Switch, Thermostat - High Engine Coolant Temperature (S2)	Sensor
309-0641-03	Switch, Oil Pressure (Closes at 14 lbs. Descending) (S1)	Sensor
309-0641-07	Switch, Oil Pressure (Closes at 20 lbs. Descending)	Sensor
960-0504	PCC Control Service Manual	Service manual
960-0507	Detector Control Service Manual	Service manual
191-1858	Starter (24VDC)	Starter
3320645	Strip, Marker - Volt. Con. Reactor (9305P218)	Strip
5208190	Stud, Fixed Resistor Mtg.	Stud
23201396	Support, Gen. Mtg.	Support
1S0A717	Switch Assy., Overspeed	Switch
FP-3076489	Thermostat	Thermostat
B-342-3s	PRIMING TURBOCHARGER OIL SUPPLY INLET LINE. DISCONNECT AT THIS POINT TO PRIME	Turbocharger
302P421	Scale Reads 0-300	Voltmeter
304A15	S Washer, Fixed Resistor Cent. to Alternator End Bell	Washer

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 NT855-G?

The Cummins/Onan NT855-G engine has an oil capacity of 14.0 liters.

What is the displacement of the Cummins/Onan NT855-G?

The Cummins/Onan NT855-G has a displacement of 14.0 liters with 6 cylinders.

Which generators use the Cummins/Onan NT855-G engine?

The Cummins/Onan NT855-G powers 4 generator set(s), including Cummins/Onan DFE 15R, Cummins/Onan DFE Series, Cummins/Onan DFP 17R, Cummins/Onan DFP 517.

How often should you change the oil in the Cummins/Onan NT855-G?

The Cummins/Onan NT855-G oil change interval is every 500 hours.

What is a common problem with the Cummins/Onan NT855-G engine?

A commonly reported issue on generators using the Cummins/Onan NT855-G is: High engine temperature shutdown. Cause: Coolant level. Fix: Check coolant level; replenish if necessary.