Cummins/Onan NTA855-G Engine Engine
The Cummins/Onan NTA855-G is a 14 L 6-cylinder turbocharged engine rated at 1800 rpm, producing up to 298.4 kW. It powers generator sets from Cummins/Onan, including the DFM Series 50Hz and DFM Series 60Hz. It holds 40 L (10.6 gal) of oil and 55 L (14.5 gal) of coolant.
Also known as: Cummins NTA855-G
Part of the Cummins/Onan NTA855 engine family — 8 variants share parts & fitment.
Engine specifications
| Oil capacity | 40.0 L |
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| Coolant capacity | 55.0 L |
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| Displacement | 14.0 L |
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| Cylinders | 6 |
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| Aspiration | Turbocharged |
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| Rated speed | 1800 rpm |
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| Gross power | 298 kW |
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Generator sets powered by this engine
2Common problems
14- Overspeed shutdown. Overspeed shutdown
Fix: Check governor and throttle linkages for freedom of movement. Check overspeed switch. - Overspeed light on, no shutdown. Overspeed light on, no shutdown
Fix: Disconnect wire at TB11-29. Light on after reset; replace engine monitor board. - 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. - Low oil pressure shutdown. *Low oil pressure shutdown
Fix: A. Oil level. Replenish if necessary. b. Sensor. Faulty sensor will shut down engine. c. Refer to engine service manual for troubleshooting guide for oil system. - Low oil pressure light ON. No shutdown. *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 shutdown. *High engine temperature shutdown
Fix: A. Coolant level. Replenish if necessary. b. City water cooled sets. Check water flow, valves, etc. c. Check sensor; check thermostat. d. Radiator model, check fan belts, radiator for obstructions, etc. - High engine temperature light ON. No shutdown. *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 TBl 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.
Fix: Check for: Overspeed condition as engine starts. - Fault lamp lights and engine shuts down after running for a period.
Fix: A. Oil level. Engine will shut down if sensor is closed. b. Check engine manual for troubleshooting oil system. c. High engine temperature. Check coolant level; check water flow (city water cooled systems); check radiator for free air flow, and fan belts for tightness. See engine manual for troubleshooting cooling system. d. Check for faulty oil pressure sensor or faulty high engine temperature sensor. - 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 position, then back to the required running position. - Engine runs, shuts down, cranks for 75-seconds, cranking cycle stops, overcrank light ON.
Fix: Check fuel supply. - Engine runs, shuts down and cranks for 75-seconds. Cranking cycle stops; fault lamp lights.
Fix: Check fuel supply. - Engine fails to start, or starts and runs then stops and fault lamp lights
Fix: Refer to appropriate troubleshooting chart, Table 3 or Table 4
Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan NTA855-G.
Maintenance schedule
| Item | Spec | Capacity | Part # | Interval | |
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| Air filter | | | — | 500 hr | find |
| Fuel filter | | | — | 500 hr | find |
| Oil filter | | | — | 500 hr | find |
| Belt | | | — | | find |
| Coolant | | 55.0 liters | — | 2000 hr | |
| Oil | ASTM D2 | 40.0 liters | — | 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 NTA855 family
23| Part # | Description | Category |
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| 140-1346 | Air Cleaner (Includes Element) | air_filter |
| 319-2236 | Bracket, Mounting | bracket |
| 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”) | bushing |
| 518-0548-58 | Clamp, Hose | clamp |
| LF3000 | Lube, Spin-On | oil_filter |
| 100-1359 | Engine, Replacement (Cummins NTA855G) | other_service |
| 102-1335 | Plug, Oil Drain | other_service |
| 309-0269 | Switch, Low Engine Temperature (S4) | other_service |
| 504-0011 | Valve, Shutoff (1/2”) | other_service |
| 505-0100 | Nipple, Pipe - Close (1/2”) | other_service |
| 526-0029 | *Washer, Flat (1/2") | other_service |
| 526-0219 | Washer, Flat (1/2) | other_service |
| 800-0048 | Screw, Cap - Hex Head (3/8-16 x 3/4”) | other_service |
| 850-0050 | Washer, Lock - Spring (3/8”) | other_service |
| 870-0212 | Nut, Locking (1/4-20) | other_service |
| 960-0138 | | other_service |
| 960-0606 | | other_service |
| 307-2621-02 | Relay, Start Solenoid (K4) | relay |
| 800-0092 | Screw, Cap - Hex Head (1/2-13 x 1.5) | screw |
| 193-0432 | Sender, Oil Temperature (S2 Engine Block, E4 Oil Pan) | sensor |
| 960-0504 | PCC Control Service Manual | service_manual |
| 960-0507 | Detector Control Service Manual | service_manual |
| 508-0292 | Washer, Sealing - Copper | 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 NTA855-G?
The Cummins/Onan NTA855-G engine has an oil capacity of 40.0 liters.
What is the displacement of the Cummins/Onan NTA855-G?
The Cummins/Onan NTA855-G has a displacement of 14.0 liters with 6 cylinders.
Which generators use the Cummins/Onan NTA855-G engine?
The Cummins/Onan NTA855-G powers 2 generator set(s), including Cummins/Onan DFM Series 50Hz, Cummins/Onan DFM Series 60Hz.
How often should you change the oil in the Cummins/Onan NTA855-G?
The Cummins/Onan NTA855-G oil change interval is every 500 hours.
What is a common problem with the Cummins/Onan NTA855-G engine?
A commonly reported issue on generators using the Cummins/Onan NTA855-G is: Overspeed shutdown.. Fix: Check governor and throttle linkages for freedom of movement. Check overspeed switch..