Cummins · Cummins D6 Commercial Diesel

Cummins C400 D6

400 kW standby / 365 kW prime · Diesel · Liquid-cooled

400 kW diesel standby generator with QSG12-G4 inline-6 engine and HPCR fuel system. EPA Tier 3 compliant, PowerCommand control, liquid-cooled, for large commercial and industrial standby applications.

Cummins Cummins C400 D6 generator — specifications and details
Standby power
400 kW / 365 kW prime
Voltage options
277/480V, 120/208V
Frequency / Phase
60 Hz · 3-phase
Engine
Cummins QSG12-G4 · 11.8L
EPA / Emissions
Tier 3
CommercialManufacturingData CentersHealthcare
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Overview#

The Cummins C400 D6 is a 400 kW standby diesel generator set powered by the QSG12-G4 -- an 11.8-liter, 6-cylinder turbocharged and charge-air-cooled engine featuring Cummins' High Pressure Common Rail (HPCR) fuel injection system. Rated at 500 kVA standby and 456 kVA prime at 60 Hz, the C400 D6 is designed for large commercial, industrial, and mission-critical standby applications where reliable power delivery with full-authority electronic engine management is essential.

The QSG12-G4 shares the same block and injection architecture as the G1 variant used in the C350 D6, with calibration changes to achieve the higher 400 kW standby output. The CM2880 ECM and Cummins Power Generation Interface (PGI) provide advanced engine protection, SAE J1939 CAN-based communications, and full integration with PowerCommand controls. Two-stage Fleetguard NanoNet fuel filtration with a water-in-fuel sensor is standard.

The C400 D6 is rated for 50 degrees C (122 degrees F) ambient operation with the standard Coolpac integrated cooling package. Open skid and enclosed configurations are available. This model occupies the top of the QSG12 power band and sits just below the QSX15-powered C450 D6 and C500 D6 in Cummins' D6 lineup.

Engineering specifications

Physical

Length
85 in
Width
45 in
Height
63 in
Dry weight
5,300 lb

Fuel system & runtime

Fuel use @ full load
28 GPH
Fuel use @ 75% load
21 GPH
Fuel use @ 50% load
15 GPH

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Estimate runtime for the Cummins C400 D6

Adjust load percent and tank size to estimate runtime. Pre-filled with this model's spec where available.

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Estimated runtime

9.3 hours(0.4 days)

Fuel consumption ≈ 21.60 GPH at 75% load. Estimate based on industry-typical 1800 RPM standby curves (≈0.07 GPH/kW at full load). Actual consumption varies by engine, ambient temperature, fuel quality, and tuning.

Service intervals

Manufacturer-recommended intervals for the Cummins C400 D6 under standby duty. Field intervals may differ based on load profile, ambient conditions, and fuel quality.

Oil & filter
Every 500 hours or 12 months
Air filter
Every 500 hours
Fuel filter
Every 500 hours
Major overhaul
≈ 30,000 hours

Common failure modes

What we've seen fail on this platform. Use as a service-planning reference, not a diagnostic — actual failure modes depend heavily on duty cycle and maintenance history.

ComponentSymptomTypical hoursSeverity
HPCR fuel injection systemInjector fault codes, rough running, power loss, fuel in oil—severe
Fleetguard two-stage fuel filterFilter clogging, reduced fuel flow, hard start under load—moderate
Charge air coolerCoolant in intake, white smoke, loss of power on high-load events—severe
CM2880 ECM connectorsIntermittent fault codes, communication errors, erratic shutdown—moderate

Frequently Asked Questions

What engine does the Cummins C400 D6 use?
The C400 D6 uses the Cummins QSG12-G4 -- an 11.8-liter, inline-6-cylinder, turbocharged and charge-air-cooled diesel with High Pressure Common Rail (HPCR) fuel injection and CM2880 ECM. EPA Tier 3 certified for stationary emergency standby applications.
What are the standby and prime ratings of the C400 D6?
Standby rating is 400 kW (500 kVA) at 60 Hz, 0.8 power factor. Prime rating is 365 kW (456 kVA). Both at 1800 rpm, 60 Hz, three-phase.
What are the service intervals for the C400 D6?
Oil and filter changes are due at 500 hours or 12 months, whichever comes first. Air filter and fuel filter replacement at 500-hour intervals. Coolant flush at 4,000 hours. Major overhaul interval is 30,000 hours, reflecting the QSG12 platform's robust displacement-to-power ratio.
How does the C400 D6 compare to the C350 D6?
Both use the QSG12 engine platform (11.8L, HPCR injection). The C400 D6 uses the G4 variant rated at 400 kW standby vs the G1 variant at 350 kW in the C350 D6. Service intervals and maintenance procedures are essentially identical across the QSG12 family.
Is the C400 D6 EPA Tier 3 compliant?
Yes. The C400 D6 is EPA Tier 3 certified for stationary emergency standby applications under 40 CFR Part 60, appropriate for large commercial and industrial standby installations throughout the United States.
Can OnPoint Generators service the C400 D6 in Northern California?
Yes. OnPoint Generators provides authorized Cummins service for large commercial diesel generators across the San Francisco Bay Area and Northern California. Our technicians are InPower-certified for CM2880 ECM diagnostics. For C400 D6 installations we recommend scheduling an annual fuel quality analysis and filter inspection alongside the standard 500-hour oil service.

Compatible equipment

Transfer switches

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