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Cummins/Onan NT-855-G3 Engine

The Cummins/Onan NT-855-G3 is an engine. It powers generator sets from Cummins/Onan, including the 250NT3 and DBBC. It holds 39.7 L (10.5 gal) of oil and 19 L (5.0 gal) of coolant.

Also known as: Cummins NT-855-G3

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

39.7 L

Oil capacity

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

Engine specifications

Oil capacity	39.7 L
Coolant capacity	19.0 L

Generator sets powered by this engine

Cummins/Onan 250NT3Cummins/Onan DBBC

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

Common problems

Engine will not crank
Cause: Fault lamp on
Fix: Correct fault and reset control
Engine cranks but will not start. OVERCRANK lamp lights and engine stops cranking. Or. Engine runs, shuts down, and LO OIL PRES lamp lights
Cause: Indicates possible fuel system or air intake problem: empty fuel tank, fuel leaks, or plugged fuel lines
Fix: Check for empty fuel tank, fuel leaks, or plugged fuel lines and correct as required
No AC output voltage
Cause: Exciter Switch not at ON position
Fix: Confirm that Exciter Switch is at ON position
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 timed 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.
PRE LO OIL PRES lamp lights. Engine continues to operate
Cause: Indicates engine oil pressure has dropped to 18 psi (124 kPa)
Fix: If generator is powering critical loads and cannot be shut down, wait until next shutdown period and then follow step 5 procedure; If engine can be stopped, follow procedure in step 5
LOW BATTERY VOLTAGE lamp lights
Cause: Poor battery cable connections
Fix: Clean the battery cable terminals and tighten all connections
LO FUEL lamp lights. Engine shuts down and LO OIL PRES lamp lights
Cause: Indicates engine has run out of fuel
Fix: Check fuel level and replenish as required
LO FUEL lamp lights. Engine continues to run
Cause: Indicates diesel fuel supply is running low
Fix: Check fuel supply and replenish as required
Engine starts from Manual Start controls but will not start automatically or from a remote panel. (Note: The Automatic Start switch must be in the Auto position for automatic or remote starting.)
Cause: A remote circuit breaker is tripped
Fix: Reset breaker and restart; Contact your distributor if breaker trips after resetting
Engine runs and then shuts down, OVERSPEED lamp lights
Cause: Indicates engine has exceeded normal operating speed
Fix: Contact your distributor for service
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 or FAULT 2
SWITCH OFF lamp flashes
Cause: Indicates Run-Stop-Remote switch is in the Stop position which will prevent automatic starting
Fix: Moving the Run-Stop-Remote switch to the Remote position will stop the lamp flashing and enable automatic starting.
Set-mounted circuit breaker tripped
Cause: The optional line circuit breaker mounts on the generator conduit box. If the load exceeds the circuit breaker current rating, the circuit breaker will open to prevent the generator from being overloaded
Fix: Locate the source of the overload and correct as required; Manually reset the breaker to reconnect the load to the generator; Optional shunt trip functions can cause the generator set to shut down and will require resetting the control
REMOTE STOP lamp lights. Engine shuts down immediately
Cause: This fault function is programmed to shut down the set immediately, as in the case of an Emergency Stop pushbutton. The nature and location of the fault is an optional selection that is determined when the set installation is designed
Fix: Refer to specifics of on-site equipment
PRE HI ENGINE TEMP lamp lights. Engine continues to operate
Cause: Indicates engine has begun to overheat and engine temperature has risen to approximately 205° F (97°C)
Fix: If generator is powering non-critical and critical loads, and cannot be shut down, use the following: Reduce load if possible by turning off non-critical loads; Check air inlets and outlets and remove any obstructions to airflow; Open doors or windows in generator area to increase ventilation. If engine can be stopped, follow procedure in step 3.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan NT-855-G3.

Service intervals

Item	Action	Hours	Months	Notes
Coolant heater	Check	8 hr
Coolant level	Check	8 hr
Generator set	Inspect	8 hr		Check for oil, fuel, cooling and exhaust leaks; check exhaust system audibly and visually with set running
Oil level	Check	8 hr
Air cleaner	Clean	50 hr		Clean if required; more often in extremely dusty conditions
Battery charging system	Check	50 hr
Drive belt tension	Check	50 hr		Visually check belts for evidence of slippage
Exhaust condensation trap	Drain	50 hr
Fuel level	Check	50 hr
Battery level/specific gravity	Check	100 hr
Fuel tanks water/sediment	Drain	100 hr		Drain 1 cup or more of fuel to remove water and sediment
Generator air outlet	Check	100 hr
Antifreeze and DCA concentration	Check	250 hr	6 mo
Crankcase oil and filter	Change	250 hr	6 mo	First service — Perform initial change after first 50 hours, subsequent changes per maintenance schedule
Generator assembly	Clean	250 hr	6 mo
Heat exchanger plugs	Check	250 hr	6 mo	If equipped
Air cleaner element	Change	500 hr	12 mo	More often in extremely dusty conditions
Coolant filter	Change	500 hr	12 mo
Cooling system	Clean	500 hr	12 mo
Crankcase breather	Clean	500 hr	12 mo	More often in extremely dusty conditions
Fuel filters	Change	500 hr	12 mo
Generator bearing	Inspect	1000 hr
Generator bearing	Replace	10000 hr	24 mo	Prime power: every 10,000 hours or two years; standby power: every five years

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	Exhaust pipe clearance to combustible wall or partition	at least 12 inches (305 mm)	inch
Clearance	Mounting base surface height above floor	at least 6 inches (152 mm)	inch
Gap	Air cleaner element cleaning nozzle distance	at least 1 inch (25 mm)	inch	low pressure compressed air 30 psi (207 kPa)
Other	Air cleaner element solvent soak time	15	minutes	Donaldson D1400 solvent or equivalent
Other	Battery specific gravity	1.260	specific gravity	1.225 recommended above 95 F (35 C) ambient; 1.280 at 80 F (27 C)
Other	Engine belt driven charging alternator output	35	ampere, 24 VDC
Other	Fuel pump lifting capacity	5 feet (1.525 m)	feet
Other	Maximum sulphated ash content of lubricating oil	1.85	percent
Other	Overcrank crank cycle	15 seconds crank / 15 seconds rest, 80-second limit	seconds
Pressure	Cranking oil priming pressure at filter head priming port	15	psi (103 kPa)	15 seconds of cranking
Pressure	Low oil pressure shutdown	12	psi (83 kPa)
Pressure	Lubrication system priming pressure	30	psi (207 kPa)	during priming
Pressure	Maximum allowable exhaust backpressure	41 inches H2O / 3.0	inches H2O / inches Hg
Pressure	Normal oil pressure range	40 to 70	psi (276 to 483 kPa)	engine at operating temperature
Pressure	Pre-low oil pressure alarm	18 or less	psi (124 kPa)
Speed	Fine speed adjustment range via Speed Adjust potentiometer	less than +100	RPM
Speed	No-load governed speed, 50 Hz 3% droop	51.5 Hz (1545 RPM)	Hz/RPM	no load
Speed	No-load governed speed, 50 Hz 5% droop	52.5 Hz (1575 RPM)	Hz/RPM	no load
Speed	No-load governed speed, 50 Hz isochronous	50.0 Hz (1500 RPM)	Hz/RPM	no load
Speed	No-load governed speed, 60 Hz 3% droop	61.8 Hz (1854 RPM)	Hz/RPM	no load
Speed	No-load governed speed, 60 Hz 5% droop	63.0 Hz (1890 RPM)	Hz/RPM	no load
Speed	No-load governed speed, 60 Hz isochronous	60.0 Hz (1800 RPM)	Hz/RPM	no load
Speed	Overspeed shutdown, 50 Hz units	approximately 1850	r/min
Speed	Overspeed shutdown, 60 Hz units	approximately 2100	r/min
Temperature	Engine temperature for cooling system flush	above 194	F (90 C)	operate engine 5 minutes
Temperature	Heat exchanger water temperature	165 to 195	F (74 to 91 C)
Temperature	High coolant temperature shutdown	223	F (106 C)
Temperature	Low coolant temperature lamp lights	70 or lower	F (21 C)
Temperature	Normal water (coolant) temperature	165 to 195	F (74 to 91 C)	depending on load and ambient temperature
Temperature	Pre-high engine coolant temperature alarm	215 or higher	F (102 C)
Torque	Oil drain plug	60-70	ft-lb (81-95 N.m)
Torque	Oil filter housing priming plug	15 to 20	ft lb (20 to 27 N.m)
Voltage	Battery voltmeter (battery condition)	26 to 28	volts	engine running
Voltage	Starting/charging DC system	24	VDC

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	Water/antifreeze mixture with DCA	Permanent type antifreeze per supplier proportion; water clean, low mineral content, free of chloride, sulphate or acid; do not use anti-leak additive antifreeze		15.5 U.S. Gal	Cooling system with standard set mounted radiator; engine only capacity 5.0 U.S. Gal (19 Litres) for NT models, 5.5 U.S. Gal (20.8 Litres) for NTA/NTTA models
Engine oil	SAE 5W grade synthetic	API class CC/CD; sulphated ash max 1.85 percent; pour point 9 F (5 C) below lowest expected temperature; viscosity 10,000 mPa.s max at -31 F (-35 C) and 4.1 mm2/s min at 212 F (100 C)	below -25°C		For ambient consistently below -13 F (-25 C) with no provision to keep engine warm. Do not use petroleum base 5W.
Engine oil	SAE 20W-40	API Class CC/CD, maximum sulphated ash 1.85 percent	above -32°C	10.5 U.S. Gal	Printed as 'Normal duty -32 F (0 C) and above - SAE 20W-40'. Refer to Cummins Engine Manual for extreme conditions. Do not mix oils of another classification or brand.
Engine oil	10W-30	Multigrade oil meeting API classification	-25°C to 25°C		Oil viscosity grade selection table: -13 to 95 F (-25 to 25 C) = 10W-30
Fuel	ASTM No. 2 Diesel Engine Fuel	Refer to Cummins Engine Manual for analysis limits; will also operate on No. 1 or similar diesel fuels			Never use galvanized fuel lines, fittings or fuel tanks

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
BATTERY CHARGER FAILURE	Battery charger failure	Fault condition of on-site battery charger (NFPA 110)	Warning	Refer to battery charger unit and remedy condition
CONTROL NOT IN AUTO	Control not in auto	Generator set is not in automatic start operation mode (flashing red)	Warning	Move Automatic Start switch to AUTO position
GEN SET UNDER LOAD	Generator set under load	Generator set is attempting to start under a load condition (NFPA 110)	Warning	Remove all loads; reset Exciter Switch to ON
LOW BATTERY VOLTAGE	Low battery voltage	Starting batteries are at low voltage condition (NFPA 110)	Warning	Clean and tighten battery cable terminals; recharge or replace battery
LOW COOLANT LEVEL	Low coolant level	Fluid level sensing switch provides engine shutdown and lights the high engine coolant temperature fault lamp	Shutdown	Check coolant level and repair leaks
LOW COOLANT TEMP	Low coolant temperature (early warning)	Engine coolant temperature marginally low for starting, 70 F (21 C) or lower; indicates inoperative coolant heater	Warning	Check coolant heater power, fuse, cord and coolant level
LOW FUEL	Low fuel	Fuel supply is low (NFPA 110)	Warning	Check fuel supply and replenish as required
LOW OIL PRESSURE	Low oil pressure (shutdown)	Engine shut down because oil pressure dropped below 12 psi (83 kPa)	Shutdown	Check oil level, lines and filters; replenish; reset control and restart; verify pressure 40 to 70 psi (276 to 483 kPa)
OVERCRANK	Overcrank	Starter locked out because of excessive cranking time (cycle cranking 15 s crank / 15 s rest, 80-second limit)	Shutdown	Place Automatic Start switch to OFF/RESET; wait two minutes for starter to cool; repeat start
OVERSPEED	Overspeed	Engine has shut down because of excessive speed (frequency detection module on generator PMG output)	Shutdown	Contact distributor for service
REMOTE STOP	Remote stop	Engine shut down because of remote signal (customer dedicated)	Shutdown	Refer to specifics of on-site equipment

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

Procedures

Electric Governor Preliminary Adjustment adjustment

Tools: Frequency meter or tachometer

Idle Speed potentiometer: turn counterclockwise 20 turns, then clockwise 10 turns (mid position).
Run Speed potentiometer: turn counterclockwise 20 turns, then clockwise 10 turns (mid position).
Gain potentiometer: turn screw fully counterclockwise.
Droop potentiometer: fully counterclockwise for isochronous, approx. 40 for 3 percent droop, approx. 80 for 5 percent droop.

Governor Gain Adjustment adjustment

Tools: Frequency meter or tachometer

Close main line circuit breaker and apply approximately 1/4 of rated load.
Make sure engine speed is constant.
Turn Gain potentiometer clockwise slowly until engine speed is not constant.
Slowly turn potentiometer counterclockwise until constant speed is achieved.
Turn potentiometer counterclockwise an additional 1/2 division.

Voltage Regulator Adjustment adjustment

⚠ Do not adjust any other voltage regulator potentiometers or rheostats; they are factory-calibrated.

Tools: Screwdriver

Loosen voltage control rheostat locking nut; turn rheostat fully counterclockwise, fully clockwise, then to mid position.
Remove cover from voltage regulator housing on engine side of generator conduit box.
With set operating and voltage monitored, adjust Coarse Voltage Potentiometer to desired generator voltage.
Perform fine voltage adjustment (+3 percent) with control rheostat and retighten locking nut.
Stop and restart generator set to confirm proper operation.
If voltage cannot be brought within range, check wiring per unit wiring diagram and repeat; contact service representative.
Shut down set and replace voltage regulator housing cover before returning to service.

Coolant Filter Service maintenance

⚠ Contact with hot coolant can result in severe burns. Allow system to cool before removing filters.

Close the shutoff valves.
Unscrew the coolant filter and discard.
Apply a light coat of lubricating oil to the gasket surface.
Install new filter, tighten by hand until seal touches filter head, then one-half to three-fourths turn more.
Open the shutoff valves.

Cooling System Flushing maintenance

⚠ Allow cooling system to cool before releasing pressure and removing radiator cap.

Disconnect coolant heater from AC power; remove radiator/expansion tank cap.
Open draincock, disconnect lower radiator hose or remove heat exchanger drain plug.
Remove pipe plug from water pump body; open cylinder block and oil cooler draincocks; drain completely.
Close block and oil cooler draincocks; replace water pump pipe plug.
Close draincock and reconnect hose or replace drain plug.
Fill with clean water, leave cap off, operate engine 5 minutes above 194 F (90 C).
Shut off engine and drain; repeat until flush water is clean.
Drain completely, then fill cooling system with proper coolant.

Crankcase Breather Cleaning maintenance

Tools: Compressed air

Remove wing nut, flat washer and rubber washer holding cover; lift cover away from filter assembly.
Lift out breather element, vapor element and gasket.
Clean all parts with approved solvent; dry with compressed air 30 psi (207 kPa).
Inspect all parts, replace if necessary.
Reassemble filter assembly, replace cover and secure.

Fuel Filter Replacement maintenance

⚠ Do not permit any flame, lit cigarette, spark, pilot light or arcing equipment near the fuel system.

Remove the fuel filters and discard.
Fill the new filters with diesel fuel and coat the sealing gasket lightly with fuel.
Install and tighten by hand until gasket just touches the filter head.
Tighten an additional one-half to three-fourths of a turn.

Heavy Duty Air Cleaner Service maintenance

⚠ Handle filters with care to prevent damage; install recommended replacement part if damaged.

Tools: Compressed air

Loosen fastener(s) and remove air cleaner housing end cap.
Remove air filter element from filter housing.
Blow low pressure compressed air 30 psi (207 kPa) through element from the clean side, nozzle at least 1 inch (25 mm) away.
Soak filter at least 15 minutes in water and Donaldsons D1400 solvent.
Rinse with clean low pressure water and air dry; do not blow dry. Reinstall when dry; replace after two cleanings.

Oil and Filter Change maintenance

⚠ Crankcase pressure can blow out hot oil; do not check oil while generator set is operating.

Tools: Waste container, Torque wrench

Warm engine to operating temperature, shut down, place Automatic Start switch OFF and disconnect negative battery cable.
Remove oil drain plug or open drain valve; collect oil; replace plug; torque to 60-70 ft-lb (81-95 N.m).
Unscrew oil filter and discard.
Coat new filter gasket with oil and fill filter with clean new oil.
Install filter, tighten 2/3 turn by hand after seal touches bracket. Do not overtighten.
Fill crankcase to high mark of dipstick.
Reconnect negative battery cable, start engine, check for oil leaks.
Shut off engine, wait 15 minutes, check oil level and add oil if required.

Priming the Fuel System maintenance

Remove each fuel filter and fill with clean fuel.
Put a light coat of fuel on the sealing gasket.
Install and tighten by hand until gasket just touches the filter head.
Tighten the filter an additional one-half to three-fourths of a turn.

Priming the Lubrication System maintenance

Tools: Priming pump with pressure gauge, Torque wrench

Remove oil inlet line from turbocharger housing, fill bearing housing with clean lubricating oil, replace and secure line.
Fill crankcase to L (low) mark on dipstick.
Remove plug from oil filter housing head and connect hand or motor-driven priming pump with pressure gauge.
Prime until 30 psi (207 kPa) pressure is obtained.
Disconnect fuel solenoid valve wire; depress Crank switch while maintaining 15 psi (103 kPa) oil priming pressure for 15 seconds.
Stop cranking, remove priming equipment, replace plug; torque to 15 to 20 ft lb (20 to 27 N.m).
Reconnect fuel shutoff valve wire; complete oil fill to H (high) mark on dipstick.

Standard Air Cleaner Replacement maintenance

Loosen the strap fastening the air intake elbow to the air cleaner housing.
Disconnect intake elbow by moving it straight away from the air cleaner.
Remove air cleaner from mounting plate and discard.
Reassemble a new air cleaner to mounting plate; secure fasteners.
Reassemble air intake elbow to air cleaner housing; secure mounting strap.

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
110/190	3	Wye	12-lead generator
110/220	1	Double delta (single phase)	12-lead generator
115/200	3	Wye	12-lead generator
115/230	1	Double delta (single phase)	12-lead generator
120/208	3	Wye	12-lead generator
120/240	1	Double delta (single phase)	U1, V1, W1, U2, V2, W2, U5, V5, W5, U6, V6, W6	Single phase, double delta connection will reduce set rating and may not work with 3-phase meters
127/220	3	Wye	12-lead generator
139/240	3	Wye	12-lead generator
200/346	3	Wye	12-lead generator
220/380	3	Wye (High/Low Wye)	12-lead generator	60 Hz and 50 Hz listed
230/400	3	Wye	12-lead generator	60 Hz and 50 Hz listed
240/416	3	Wye	12-lead generator	60 Hz and 50 Hz listed
254/440	3	Wye	12-lead generator	60 Hz and 50 Hz listed
277/480	3	Wye	12-lead generator
Medium voltage (601V to 15kV)	3	6 lead generator	6-lead generator	Drawing number 3052056 (sht. 2) pertains to medium voltage, 6 lead generators, where applicable

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 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 NT-855-G3?

The Cummins/Onan NT-855-G3 engine has an oil capacity of 39.7 liters.

Which generators use the Cummins/Onan NT-855-G3 engine?

The Cummins/Onan NT-855-G3 powers 2 generator set(s), including Cummins/Onan 250NT3, Cummins/Onan DBBC.

What is a common problem with the Cummins/Onan NT-855-G3 engine?

A commonly reported issue on generators using the Cummins/Onan NT-855-G3 is: Engine will not crank. Cause: Fault lamp on. Fix: Correct fault and reset control.