The Cummins/Onan QSK78-G9 is a 78 L 18-cylinder turbocharged and low temperature after-cooled engine rated at 1500 rpm, producing up to 2304 kW. It powers generator sets from Cummins/Onan, including the C3000 D5 and QSK78.
Also known as: Cummins QSK78-G9
Part of the Cummins/Onan QSK78 engine family — 9 variants share parts & fitment.
| Displacement | 78.0 L |
|---|---|
| Cylinders | 18 |
| Aspiration | Turbocharged and low temperature after-cooled |
| Rated speed | 1500 rpm |
| Gross power | 2304 kW |
How to read your Cummins/Onan engine serial & model number →
| Item | Action | Hours | Months | Notes |
|---|---|---|---|---|
| Lubricating oil | Test | 250 hr | 6 mo | First service — For high horsepower engines with Eliminator™ oil filter option: take oil samples every 250 hours and analyze per Cummins Engine Oil Recommendations Bulletin 3810340; repeat for at least three oil change intervals. |
| ELIMINATOR self cleaning filter core | Other | 1500 hr | Requires servicing only every 1,500 hours. Saves up to 90% of lube system maintenance costs and increases productivity. | |
| valve clearance | Check | 2000 hr | B-Series (4BT3.3): valve clearance checks not required for 2000 hours, twice the industry standard | |
| engine overhaul | Other | 20000 hr | QSK23-Series: expected life cycle to 20,000 hours before first overhaul |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
| Type | Item | Value | Unit | Condition |
|---|---|---|---|---|
| Other | DB9F-DB9M serial cable length (Part Number 4918418) | 1.83 | M | |
| Other | Extension DB9F to DB9M length (Part Number 3162851) | 30.48 | M | |
| Other | INLINE™5 datalink adapter current requirement | 250 | mA | at +8 VDC to +50 VDC |
| Other | USB cable length (Part Number 4918419) | 2 | M | |
| Other | USB cable length (Part Number 4918591) | 5 | M | |
| Voltage | INLINE™5 datalink adapter supply voltage (maximum) | +50 | VDC | power lamp fast flashing indicates greater than maximum |
| Voltage | INLINE™5 datalink adapter supply voltage (minimum) | +8 | VDC | power lamp slow flashing indicates less than minimum |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
| Fluid | Grade | Standard | Ambient | Capacity | Notes |
|---|---|---|---|---|---|
| Engine oil | Cummins Engine Oil Recommendations Bulletin 3810340 | Used to analyze oil samples for high horsepower engines with Eliminator™ oil filter option. | |||
| Fuel | B100 biodiesel | ASTM D6751 | Must conform prior to blending; revised to include a cold soak test; stability requirement still in effect. | ||
| Fuel | B20 biodiesel blend | ASTM D7467 | Applies to biodiesel blends B6–B20; includes oxidation stability requirement; replaces Cummins' previous EMA B20 specification requirement. Must be purchased from a BQ9000 Certified Marketer; B100 must be sourced from a BQ9000 Accredited Producer. | ||
| Fuel | B5 biodiesel | All Cummins automotive and industrial engines are compatible with B5 biodiesel. | |||
| Fuel | biodiesel (Europe) | EN 14214 | Published by CEN, European Committee for Standardization. Equivalent biodiesel specifications required internationally. |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
⚠ A fully populated USB cable, Part Number 4918419, or DB9F-DB9M serial cable, Part Number 4918418, must be used.
⚠ B20 has a solvent nature and may clean the vehicle fuel tank and lines.
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
| Part # | Description | Category |
|---|---|---|
| 0140-3963 | Filter, Air - Standard Duty | Air filter |
| A034R952 | Filter, Air - Heavy Duty | Air filter |
| A034R957 | Element, Primary - Heavy Duty | Air filter |
| A034R963 | Secondary, Primary - Heavy Duty | Air filter |
| 5572840 | Cylinder Head Lifting Handle Kit | Service part / kit |
| 5573037 | Camshaft Removal & Installation Kit | Service part / kit |
| 908-0600 | Cummins QSK78 Series Engine Operation and Maintenance Manual | Service part / kit |
| A041X654 | Element, Replacement - Crankcase Breather | Service part / kit |
| APCH-1007-12 | Bulletin 5600277 | Service part / kit |
Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.
The Cummins/Onan QSK78-G9 has a displacement of 78.0 liters with 18 cylinders.
The Cummins/Onan QSK78-G9 powers 2 generator set(s), including Cummins/Onan C3000 D5, Cummins/Onan QSK78.