What engine does the Cummins C40 D6 use?

The C40D6 uses the Cummins 4BT3.3-G5, a 3.3-liter, turbocharged, inline-4-cylinder diesel rated at 1800 rpm. EPA Tier 3 certified. It is the same engine block used across the C25 through C60 diesel range, calibrated for 40 kW standby output -- the highest rating on the 4BT3.3-G5 variant.

What are the standby and prime ratings of the C40 D6?

Standby rating is 40 kW (50 kVA) at 60 Hz, 0.8 power factor. Prime rating is 36 kW (45 kVA). Both at 1800 rpm.

What are the service intervals for the C40 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 3,000 hours or 24 months.

How does the C40 D6 compare to the C60 D6?

The C40D6 uses the 4BT3.3-G5 engine at 40 kW standby, while the C60D6 uses the higher-output 4BT3.3-G7 variant (or the QSB5-G13 in the C60D6C model) at 60 kW standby. If your load profile exceeds 40 kW, the C60D6 provides the necessary headroom.

Can {company} service the C40 D6 in Northern California?

Yes. PowerGen serves the San Francisco Bay Area, Silicon Valley, and broader Northern California with generator service. We carry 4BT3.3 parts and provide annual maintenance, load bank testing, and emergency response for C40 D6 installations.

Cummins · Cummins D6 Commercial Diesel

Cummins C40 D6

Name: Cummins C40 D6
Brand: Cummins
SKU: c40-d6

40 kW standby / 36 kW prime · Diesel · Liquid-cooled

40 kW EPA Tier 3 diesel standby generator with Cummins 4BT3.3-G5 engine and PowerCommand 1.1 control. Sound-attenuated enclosure, liquid-cooled, for small commercial and light-industrial standby.

Standby power: 40 kW / 36 kW prime
Voltage options: 120/240V, 120/208V, 277/480V
Frequency / Phase: 60 Hz · 1/3-phase
Engine: Cummins 4BT3.3-G5 · 3.3L
EPA / Emissions: Tier 3

Commercial Residentiallight-industrial

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Overview#

The Cummins C40 D6 (model designation C40D6) is a 40 kW standby diesel generator set powered by the Cummins 4BT3.3-G5 engine -- a 3.3-liter, turbocharged, 4-cylinder industrial diesel running at 1800 rpm. Rated at 50 kVA standby and 45 kVA prime at 60 Hz, the C40D6 represents the top of the 4BT3.3-G5 power range before the step up to the higher-output G7 variant used in the C50D6 and C60D6.

Standard equipment includes the PowerCommand 1.1 control with integrated voltage regulation and a sound-attenuated enclosure. The unit is EPA Tier 3 certified for stationary emergency standby applications.

The C40D6 is well-suited for small commercial buildings, restaurants, and light-industrial facilities where the total standby load requirement falls in the 30-40 kW range.

Our Service Experience#

At 40 kW, the 4BT3.3-G5 engine is working near its upper output limit. We pay closer attention to turbocharger condition on the C40D6 compared to the lower-rated C25 and C35 units on the same block. Annual turbo inspections should include checking shaft play and oil seal integrity. The PowerCommand 1.1 control is straightforward to service -- most diagnostics can be performed through the front panel without specialized software.

Frequently Asked Questions#

Is the C40 D6 the largest generator on the 4BT3.3-G5 engine? Yes. The C40D6 is the highest-rated generator set using the 4BT3.3-G5 variant. The next step up, the C50D6, uses the 4BT3.3-G7 engine with a higher-output turbocharger configuration.

What voltages are available? The C40D6 is available in 120/240V single-phase, 120/208V three-phase, and 277/480V three-phase configurations.

Engineering specifications

Physical

Length: 90 in
Width: 36 in
Height: 50 in
Dry weight: 1,700 lb

Fuel system & runtime

Fuel use @ full load: 3.7 GPH
Fuel use @ 50% load: 2.2 GPH

Documents & downloads

Spec sheets & manuals

Spec sheet (datasheet)

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Estimate runtime for the Cummins C40 D6

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

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Generator size

Fuel

Fuel tank capacity

gal

Load

Override full-load GPH (optional)

GPH

Estimated runtime

70.1 hours(2.9 days)

Fuel consumption ≈ 2.85 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 C40 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: ≈ 20,000 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.

Component	Symptom	Typical hours	Severity
4BT3.3 turbocharger oil seal	Blue exhaust smoke at startup, increased oil consumption	—	moderate
PowerCommand 1.1 speed sensing	Engine hunting, erratic frequency, crank-no-start	—	moderate
Spin-on lube oil filter seal	Oil seepage at filter base, low oil pressure warning	—	minor

Frequently Asked Questions

What engine does the Cummins C40 D6 use?: The C40D6 uses the Cummins 4BT3.3-G5, a 3.3-liter, turbocharged, inline-4-cylinder diesel rated at 1800 rpm. EPA Tier 3 certified. It is the same engine block used across the C25 through C60 diesel range, calibrated for 40 kW standby output -- the highest rating on the 4BT3.3-G5 variant.
What are the standby and prime ratings of the C40 D6?: Standby rating is 40 kW (50 kVA) at 60 Hz, 0.8 power factor. Prime rating is 36 kW (45 kVA). Both at 1800 rpm.
What are the service intervals for the C40 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 3,000 hours or 24 months.
How does the C40 D6 compare to the C60 D6?: The C40D6 uses the 4BT3.3-G5 engine at 40 kW standby, while the C60D6 uses the higher-output 4BT3.3-G7 variant (or the QSB5-G13 in the C60D6C model) at 60 kW standby. If your load profile exceeds 40 kW, the C60D6 provides the necessary headroom.
Can PowerGen service the C40 D6 in Northern California?: Yes. PowerGen serves the San Francisco Bay Area, Silicon Valley, and broader Northern California with generator service. We carry 4BT3.3 parts and provide annual maintenance, load bank testing, and emergency response for C40 D6 installations.

Compatible equipment

Transfer switches

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