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Cummins/Onan QSK23 series Engine

The Cummins/Onan QSK23 series is a 23.15 L 6-cylinder turbocharged engine rated at 1500 rpm, producing up to 1000 kW. It powers generator sets from Cummins/Onan, including the C750 D6, C800 D6, CFP23E and CFP23E-F10. It holds 12 L (3.2 gal) of oil and 12 L (3.2 gal) of coolant.

Also known as: Cummins QSK23 series

Part of the Cummins/Onan QSK23 engine family — 10 variants share parts & fitment.

23.15 L

Displacement

Cylinders

1500 rpm

Rated speed

1000 kW

Gross power

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

Engine specifications

Oil capacity	12.0 L
Coolant capacity	12.0 L
Displacement	23.15 L
Cylinders	6
Aspiration	Turbocharged
Rated speed	1500 rpm
Gross power	1000 kW

Generator sets powered by this engine

Cummins/Onan C750 D6 Cummins/Onan C800 D6 Cummins/Onan CFP23ECummins/Onan CFP23E-F10Cummins/Onan CFP23E-F20Cummins/Onan D-3352-DC Cummins/Onan DQCA Cummins/Onan DQCB Cummins/Onan DQCC Cummins/Onan Dacc Cummins/Onan QSK23

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

Common problems

Over Current 1471
Low Coolant Level 197
Emergency Stop
Fix: Annunciated whenever either emergency stop signal is received from external switch.
Weak battery warning
Fix: The control system will test the battery each time the generator set is signaled to start and indicate a warning if the battery indicates impending failure.
Weak Battery 1442
Under frequency shutdown 81 u
Fix: Generator set output frequency cannot be maintained. Settings are adjustable from 2-10 Hz below reference governor set point, for a 5-20 second time delay. Default: 6 Hz, 10 seconds. Over frequency shutdown/warning is disabled when excitation is switched off, such as when engine is operating in idle speed mode.
Under Frequency 1448
Too Long in Idle 2342
Speed/Hz Match 1469
Speed Signal Lost 121
Shutdown After Battle Short 1123
Short Circuit 1445
Reverse power shutdown
Fix: Adjustment range: 5
Remote Emergency Stop 1434
Pre-Low Oil Pressure Sensor 143

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan QSK23 series.

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Air filter	AF25544		AF25544		Amazon eBay $285.93 NAPA $391.96
Fuel filter	FS1006		FS1006		Amazon eBay $29.99 NAPA $90.16
Oil filter	Full-flow with by-pass valve		LF9325	250 hr	Amazon eBay $127.04 KuduParts $74.00 FridayParts $75.99
Battery	526−0112		A048G602	500 hr	eBay
Belt	Direct drive centrifugal blower fan		—	15000 hr
Coolant	Antifreeze 50/50 (Ethylene glycol)		—	24000 hr
Coolant filter	503−1675		—	500 hr
Oil	Cummins QuickServe® Commitment	54.8 U.S. QT	—	250 hr
Spark plug	151−0411		—	500 hr

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.

Service intervals

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.
filters	Change	1000 hr		with CENTINEL, depending on load factors
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.
fuel filter	Change	1500 hr		Fleetguard NanoNet media
valve clearance	Check	2000 hr		B-Series (4BT3.3): valve clearance checks not required for 2000 hours, twice the industry standard
engine oil	Change	4500 hr		with CENTINEL, railway applications
engine overhaul	Other	20000 hr		QSK23-Series: expected life cycle to 20,000 hours before first overhaul
Coolant pump	Inspect		24 mo	Every two years
Coolant pump/alternator belt	Inspect		12 mo	Annual
Coolant pump/alternator belt	Replace		48 mo	Every four years
Coolant thermostat	Replace		48 mo	Every four years (removal/installation)
Cooling system - heat exchanger	Clean		24 mo	Drain and flush if contaminated
Cooling system - heat exchanger	Drain		24 mo	Every two years; drain and flush the cooling system
Drive shaft	Lubricate		12 mo	Grease universal joint fittings
Electrical components	Inspect		12 mo	Annual
Electrical components, wiring harness, gauges	Inspect		12 mo
Engine oil and filter	Change		12 mo	Change the oil at least once annually
Engine supports	Inspect		12 mo	Check torque on support capscrews
Fuel pumps and filters	Inspect		12 mo	Annual
Heat exchanger	Test		12 mo	Pressure test
Raw water zinc anode	Inspect		12 mo	Replace if eroded more than 50%
Turbocharger	Inspect		12 mo	Annual
Turbocharger mounting nuts	Adjust		12 mo	Torque to recommended value
Turbocharger mounting nuts	Check		12 mo	Annual; torque to recommended value
Valve lash	Adjust		48 mo	Every four years; by a skilled technician

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	Belt tensioner spring case to arm maximum clearance	3	mm
Other	AC waveform THD (THDV)	< 5	%	no load to full linear load
Other	AC waveform Total Harmonic Distortion (THDV)	< 5 no load to full linear load, < 3 for any single harmonic	%
Other	BMEP at set rated load (prime)	1885	kPa	prime rating
Other	BMEP at set rated load (standby)	2109	kPa	standby rating
Other	Battery specific gravity (fully charged)	1.260
Other	Battery specific gravity (replace threshold)	1.215
Other	Battery specific gravity replacement threshold	1.215		below this value replace the battery
Other	Battery specific gravity, fully charged	1.260
Other	Breaker fail to synchronize default time delay	120	s	adjustable 10–900 s
Other	Compression ratio	16:1
Other	DB9F-DB9M serial cable length (Part Number 4918418)	1.83	M
Other	Derate above 1402 m (4600 ft) / 40 °C	4.5% per 305 m (1000 ft) and 11.0% per 10 °C (18 °F)		standby and prime
Other	Extension DB9F to DB9M length (Part Number 3162851)	30.48	M
Other	High AC voltage shutdown default	110%	% of nominal voltage	for 10 s; adjustable 105–125%, 0.1–10 s
Other	INLINE™5 datalink adapter current requirement	250	mA	at +8 VDC to +50 VDC
Other	Instantaneous pickup (Ii) range (Micrologic 3.0 and 5.0)	1.5–12 x In	x In
Other	Long-time delay tr	0.5–24	s	at 6 x Ir
Other	Long-time pickup (Ir) adjustment range	0.4–1.0 x In	x In	sensor plug rating In
Other	Low AC voltage shutdown default	85%	% of reference voltage	for 10 s; adjustable 50–95%, 2–20 s
Other	Maximum resistance of starting circuit	0.002	Ohms	12V
Other	Maximum resistance of starting circuit	0.004	Ohms	24V
Other	Over frequency shutdown/warning default	6	Hz above nominal	for 20 s, disabled; adjustable 2–10 Hz above set point, 1–20 s
Other	Over load (kW) warning default	105%	% of rated kW	adjustment range 80–140%, 0–120 s delay; default 60 s
Other	Piston speed	11.4	m/s
Other	Pressure sensing line nominal size inside diameter	1/2	in. (12.7 mm)	connected between the transducer (located under the FPDP) and the pump discharge flange and the discharge check valve
Other	Reverse Var shutdown default	20%	% of rated Var	for 10 s; adjustable 15–50%, 10–60 s
Other	Reverse power shutdown default	10%	% of standby kW	for 3 s; adjustable 5–20%, 1–15 s
Other	Short circuit protection threshold	175%	% of rating	output current on any phase
Other	Telephone Harmonic Factor (THF)	< 3
Other	Telephone Influence Factor (TIF)	< 50	per NEMA MG1-22.43
Other	USB cable length (Part Number 4918419)	2	M
Other	USB cable length (Part Number 4918591)	5	M
Other	Under frequency shutdown default	6	Hz below reference	for 10 s; adjustable 2–10 Hz below set point, 5–20 s
Other	Wire stripping length	1.38 In (35 mm)	in
Pressure	BMEP at set rated load	2214	kPa	prime rating
Pressure	BMEP at set rated load	2435	kPa	standby rating
Pressure	Coolant expansion pressure/fill cap minimum pressure	10	kPa (15 psi)
Pressure	Cooling loop cooling water pressure limit	270	psi	installations where the discharge pressure is greater than 270 psi (pressure reducing valve required upstream of the cooling loop)
Pressure	Cooling loop pressure regulator setting	276	kPa (40 psi)
Pressure	Cooling loop pressure regulator setting	345	kPa (50 psi)
Pressure	Discharge set point pressure / maximum control pressure	100/110, 170/175, or 240/250	psi	set by the factory and not adjustable; specify at time of order
Pressure	Heat exchanger pressure test	276	kPa (40 psi)	air pressure applied; monitor 5 minutes
Pressure	Heat exchanger pressure test (applied air)	276	kPa	hold 5 minutes, no pressure change
Pressure	Maximum air cleaner restriction	6.2	kPa
Pressure	Maximum back pressure	10.1	kPa
Pressure	Maximum back pressure	6.8	kPa	exhaust
Pressure	Maximum cooling air flow static restriction	0.12	kPa
Pressure	Maximum cooling water pressure on local gauge	414	kPa (60 psi)
Pressure	Maximum fuel inlet restriction	13.44	kPa
Pressure	Maximum fuel inlet restriction	30	kPa
Pressure	Maximum fuel return line restriction	34	kPa
Pressure	Minimum oil pressure during test run	69	kPa (10 psi)	engine running
Pressure	Oil pressure minimum during test run	69	kPa	running
Pressure	Oil pressure range at rated	276-414	kPa	at rated
Pressure	Oil pressure range at rated	40-60	PSI (276-414 kPa)	at rated
Pressure	Raw water working pressure range at heat exchanger	60	PSI (413 kPa) MAX
Pressure	VSPLC set point range	100 to 400	psi
Pressure	VSPLC transducer pressure offset limit	+/-10	PSI	resolution 0.1 PSI
Resistance	Maximum resistance of starting circuit	0.001	Ohms

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	Ethylene-Glycol 40% = -23 C (-10 F); 50% = -37 C (-34 F); 60% = -54 C (-65 F); 68% = -71 C (-96 F)		above -71°C		Freeze protection chart
Coolant	Propylene-Glycol 40% = -21 C (-6 F); 50% = -33 C (-27 F); 60% = -54 C (-65 F); 68% = -63 C (-82 F)		above -63°C		Freeze protection chart
Coolant	50% ethylene glycol antifreeze and 50% water	Fleetguard ES COMPLEAT EG or Fleetguard PG Plus	above -37°C	22.3 L (engine only)	Use 50% concentration (40% to 60% range) with SCA required for wet-sleeved engines. Antifreeze at 68% provides maximum freeze protection and must never be exceeded. Use soft or distilled water not exceeding 300 ppm hardness.
Coolant	50% ethylene-glycol / 50% water	Fleetguard ES COMPLEAT EG or Fleetguard PG Plus	above -37°C	12.3 L	Antifreeze concentration chart: 40%=-23C, 50%=-37C, 60%=-54C, 68%=-71C; never exceed 68%
Engine oil		Cummins Engine Oil Recommendations Bulletin 3810340			Used to analyze oil samples for high horsepower engines with Eliminator™ oil filter option.
Engine oil	15W-40	Premium Blue or equivalent			Cummins recommends Premium Blue 15W-40 oil for most climates. Do not use special break-in oils. Oil capacity of pan (high-low) 20-16 qt (18.9-15.1 L); total system capacity 6.3 gal (23.8 L).
Fuel	ASTM D975 No. 2-D	ASTM D975			Cetane number: 40-50. 300-500 ppm Sulfur. Fuel inlet temperature 40°C (104°F) reference.
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	No. 2 diesel	ASTM no. 2D			Do not use copper or galvanized pipe for supply/return lines
Fuel	No. 2 diesel (ASTM no. 2D)	ASTM no. 2 diesel fuel specifications			Use ONLY no. 2 diesel fuel. Do not mix gasoline, alcohol, gasohol, ethanol, or methanol with diesel fuel.
Fuel	biodiesel (Europe)	EN 14214			Published by CEN, European Committee for Standardization. Equivalent biodiesel specifications required internationally.
Fuel	number 2 diesel fuel				Direct injection, fuel filter, automatic electric fuel shutoff
Grease	NLGI #2 lithium complex	Good quality semi-synthetic, molybdenum-fortified	-47°C to 204°C		For drive shaft universal joint grease fittings; protects from -47 to 204 C (-54 to 400 F).

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
27	Low AC voltage shutdown	Voltage on any phase has dropped below a preset value.	Shutdown	Adjustable 50-95% of reference voltage, time delay 2-20 seconds; default 85% for 10 seconds.
32	Reverse power shutdown	Reverse power detected.	Shutdown	Adjustment range 5-20% of standby kW rating, delay 1-15 seconds; default 10%, 3 seconds.
40	Reverse Var shutdown	Reverse reactive power detected.	Shutdown	Adjustable 15-50% of rated Var output, delay 10-60 seconds; default 20%, 10 seconds.
46	Negative sequence overcurrent warning	Excessive imbalances in the three phase load currents and/or power factors.	Warning	Control protects generator from damage due to phase imbalance.
51	Overcurrent warning/shutdown	Implementation of the thermal damage curve with instantaneous trip level based on CT ratio and application power rating.	Shutdown	AmpSentry protective relay action; see document R1053 time over current curve.
51G	Ground fault overcurrent	Detects a ground fault via external ground fault relay contact input or measured ground current from external CT.	Shutdown	Time delays and thresholds adjustable via InPower or HMI.
59	High AC voltage shutdown	Output voltage on any phase exceeds preset values; trip time inversely proportional to amount above threshold.	Shutdown	Adjustable 105-125% of nominal voltage, time delay 0.1-10 seconds; default 110% for 10 seconds.
81 o	Over frequency shutdown/warning	Generator set is operating at a potentially damaging frequency level. Settings adjustable from 2-10 Hz above nominal governor set point for a 1-20 second time delay. Default: 6 Hz, 20 seconds, disabled.	Warning
81 u	Under frequency shutdown	Generator set output frequency cannot be maintained. Settings adjustable from 2-10 Hz below reference governor set point, for a 5-20 second time delay. Default: 6 Hz, 10 seconds.	Shutdown
81o	Over frequency shutdown/warning	Genset is operating at a potentially damaging frequency level.	Warning	Adjustable 2-10 Hz above nominal governor set point, 1-20 second delay; default 6 Hz, 20 seconds, disabled.
81u	Under frequency shutdown	Genset output frequency cannot be maintained.	Shutdown	Adjustable 2-10 Hz below reference governor set point, 5-20 second delay; default 6 Hz, 10 seconds.
111	Engine Control Module Critical Internal Failure	Engine Control Module Critical Internal Failure - Bad Intelligent Device or Component	Shutdown
115	Engine Speed/Position Sensor Circuit	Engine Speed/Position Sensor Circuit - lost both of two signals from the magnetic pickup sensor - Data Erratic	Shutdown
122	Intake Manifold Pressure Sensor Circuit	Intake Manifold Pressure Sensor Circuit - Voltage Above Normal, or Shorted to High Source	Warning
123	Intake Manifold Pressure Sensor Circuit	Intake Manifold Pressure Sensor Circuit - Voltage Below Normal, or Shorted to Low Source	Warning
135	Oil Pressure Sensor Circuit	Oil Pressure Sensor Circuit - Voltage Above Normal, or Shorted to High Source	Warning
141	Oil Pressure Sensor Circuit	Oil Pressure Sensor Circuit - Voltage Below Normal, or Shorted to Low Source	Warning
143	Oil Pressure Low	Oil Pressure Low - Data Valid But Below Normal Operational Range - Moderately Severe Level	Warning
144	Coolant Temperature Sensor Circuit	Coolant Temperature Sensor Circuit - Voltage Above Normal or Shorted to High Source	Warning
145	Coolant Temperature Sensor Circuit	Coolant Temperature Sensor Circuit - Voltage Below Normal or Shorted to Low Source	Warning
146	Coolant Temperature High	Coolant Temperature High - Data Valid But Above Normal Operational Range - Moderately Severe Level	Warning
151	Coolant Temperature Low	Coolant Temperature Low - Data Valid But Above Normal Operational Range - Most Severe Level	Shutdown
221	Barometric Pressure Sensor Circuit	Barometric Pressure Sensor Circuit - Voltage Above Normal, or Shorted to High Source	Warning
234	Engine Speed High	Engine Speed High - Data Valid But Above Normal Operational Range - Most Severe Level	Shutdown
235	Coolant Level Low	Coolant Level Low - Data Valid But Below Normal Operational Range - Most Severe Level	Shutdown
415	Oil Pressure Low	Oil Pressure Low - Data Valid But Below Normal Operational Range - Most Severe Level	Shutdown
418	Water in Fuel Indicator High	Water in Fuel Indicator High - Data Valid But Above Normal Operational Range - Least Severe Level	Warning
441	Auxiliary Temperature Sensor Input #1	Auxiliary Temperature Sensor Input #1 - Special Instructions	Shutdown
442	Auxiliary Pressure Sensor Input #1	Auxiliary Pressure Sensor Input #1 - Special Instructions	Shutdown
451	Injector Solenoid Cylinder #1 Circuit	Injector Solenoid Cylinder #1 Circuit - Current Below Normal, or Open Circuit	Warning
452	Injector Solenoid Cylinder #5 Circuit	Injector Solenoid Cylinder #5 Circuit - Current Below Normal, or Open Circuit	Warning
453	Injector Solenoid Cylinder #3 Circuit	Injector Solenoid Cylinder #3 Circuit - Current Below Normal, or Open Circuit	Warning
561	Injector Solenoid Cylinder #5	Injector Cylinder #5 - Mechanical System Not Responding Properly or Out Of Adjustment	Warning
689	ECM Program Memory (RAM) Corruption	ECM Program Memory (RAM) Corruption - Condition Exists	Warning
731	Starter Relay Circuit	Starter Relay Circuit - Voltage Above Normal, or Shorted to High Source	Warning
755	ECM Data Lost	Electronic Control Module data lost - Condition Exists	Warning
1117	Power Lost With Ignition On	Power Lost With Ignition On - Data Erratic, Intermittent, or Incorrect

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

Procedures

Engine speed adjustment (CFP83 F-10, F-20, F-30) adjustment

⚠ The maximum engine speed should only be altered by a Cummins technician.

Start the engine.
Observe that the engine accelerates to the currently adjusted speed setpoint.
Locate the threaded linkage rod on the fuel pump side of the engine.
Loosen the locking nuts against the stops on the threaded rod.
To increase speed, turn the bolt on the right side of the throttle bracket clockwise.
To decrease speed, turn the bolt counter-clockwise.
When the rated speed is correct, tighten the locking nut against the stop.
Adjust the left-side threaded bolt for maximum speed if needed.
Stop the engine and repeat until the desired speed is attained.

Heat exchanger pressure test diagnostic

⚠ Use Teflon tape or pipe sealant when installing test setup.

Tools: pressure gauge 689 kPa (100 psi)

Install an adapter at the cooling water outlet of the heat exchanger.
Install a pressure test setup with 689 kPa (100 psi) gauge at the cooling water inlet.
Apply air pressure at 276 kPa (40 psi).
Isolate pressure source and monitor gauge for five minutes.
Release pressure and remove test equipment.

Overspeed test diagnostic

From the User Interface screen press the MENU soft key.
Press the OVERSPEED TEST soft key from the Settings Menu.
Press the RUN soft button.
When the dialog box appears, proceed with the test and select Yes.
When the timer expires, ENGINE OVERSPEED flashing in red appears at the top of the FPDP screen.
The engine will enter MANUAL mode until reset.
Press the RESET/STOP switch on the FPDP to reset the fire pump drive engine.

Terminal block test diagnostic

Tools: Digital multimeter

From the User Interface screen press the MENU soft key.
Press the ENGINE SETUP soft key from the Settings menu.
Enter password 806 in the Engine Setup Login screen.
Press the TERMINAL BLOCKS soft key from the Engine Setup menu.
Press the soft key corresponding to the terminal block requiring verification.
Press the RETURN soft key to exit the Terminal Block Test menu.

Trip Unit Operation Verification diagnostic

Tools: Trip unit test kit

Connect a test kit to the trip unit test plug receptacle.
Perform verification tests per instructions shipped with the test kit to verify trip unit functions.

Battery installation installation

⚠ Battery electrolyte (sulfuric acid) is highly caustic.

⚠ Batteries can emit explosive gases during charging.

⚠ Remove the negative (-) battery cable first and attach it last.

Tools: Neoprene gloves, Safety goggles or full face shield

Install the battery cable kit or equivalent customer-supplied wiring.
Install battery sets in a well-ventilated or otherwise protected location.
Provide adequate room for servicing or replacing the batteries.
Locate the batteries near the engine or increase conductor size as required.
Check the battery cables and connections.
Coat the terminals with petroleum jelly to prevent corrosion.

Connect the INLINE™5 Datalink Adapter to a Personal Computer installation

⚠ A fully populated USB cable, Part Number 4918419, or DB9F-DB9M serial cable, Part Number 4918418, must be used.

Connect the DB9F-DB9M serial cable, Part Number 4918418, or USB cable, Part Number 4918419, to the computer.
Connect the other end of that cable to the INLINE™5 datalink adapter, Part Number 3165033.
Supply +8 VDC to +50 VDC at 250mA through the OEM connector or a separate power source.
Connect the appropriate datalink cable to the INLINE™5 datalink adapter, Part Number 3165033.
Connect the other end of the datalink cable to the vehicle cab or engine compartment datalink connector.
Launch the electronic service tool application software.

Cooling water supply installation installation

⚠ The cooling water supply must be immediately available when the engine is started.

⚠ Do not operate without a pressure cap.

Tools: Appropriate-sized container

Provide a cooling water discharge line at the heat exchanger outlet and a supply line to the cooling water inlet.
Check the pressure regulator setting on the cooling loop with water flowing through the heat exchanger.
Adjust the cooling water based on water flow rather than water pressure.
Measure the water flow using a container and elapsed time.
Adjust both pressure regulators to provide flow at or above specifications.

Drive shaft installation installation

⚠ Do not use the engine lifting points for assembly!

Tools: Lifting device, Grease gun

Ensure the engine and pump are correctly aligned.
Verify engine position centered on frame side to side within +/- .76 mm (.03 in).
Align engine center line to pump center line within +/- .76 mm (.03 in).
Ensure pump center line to engine crankshaft center line (vertical) is 2 degrees +/- 1 degree.
Ensure drive shaft mounting flanges are parallel.
Lubricate the grease fittings on the drive shaft universal joint.
Check engine is installed per pump manufacturer's specifications.

Fuel supply installation installation

⚠ Do not use copper or galvanized pipe for the fuel return or supply lines.

⚠ Do not mix gasoline, alcohol, gasohol, ethanol, or methanol with diesel fuel.

Tools: Container for contaminated fuel

Install an elevated no. 2 diesel fuel tank or equivalent compatible with ASTM no. 2 diesel specifications.
Size the fuel tank for the maximum expected full-load operation period.
Install a fuel return line routed to the bottom of the fuel tank.
Install a fuel supply line to the fire pump drive engine.
Open the fuel filter/water separator drain and drain until no water is present.

Battery replacement / battery rack installation maintenance

Isolate DC supply before working on battery connections.
Install battery rack with hold-down, floor standing.
Install battery with minimum 2200 amps capacity at -18 °C to 0 °C.
Verify 24 volt negative ground connection.

Coolant pump/alternator belt inspection maintenance

⚠ Disconnect batteries (negative cable first) before service.

Tools: Cummins belt tension gauge 3822524

Place engine in MANUAL and disconnect both batteries (negative first).
Remove belt guard capscrews and belt guard.
Visually inspect belt for frayed, worn, missing pieces or intersecting cracks.
Check belt tension using Cummins belt tension gauge 3822524 at center span.
Reinstall battery cables (negative last).

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
120/208	3	Wye	12/6	Winding 311/312; ADS-631; feature code BC38-2
120/240	3	Delta	12/6	Winding 311/312
12470-13800	3	Wye, 3-phase	Winding no. 6062	Temp rise 125/105/80 °C; ADS-521; feature code B448; max surge kVA 91
127/220	3	Wye	12/6	Winding 311/312
133/230	3	Wye	12/6	Winding 311/312
139/240	3	Wye	12/6	Winding 311/312
190-480		Wye		Temp rise 125/105 degrees C; Duty S/P; Max surge 2944 kVA; Winding No. 311; ADS-309; Feature code B731-2
190/380	3	Wye		Winding 311; ADS-631; feature code BC37-2
200/400	3	Wye		Winding 311; ADS-310; feature code BC35-2
208/416		Wye		Temp rise 105/80 degrees C; Duty S/P; Max surge 2944 kVA; Winding No. 311; ADS-309; Feature code B733-2
208/416	3	Wye		Winding 311; ADS-632; feature code BC44-2
220/380		Wye		Temp rise 105/80 degrees C; Duty S/P; Max surge 3313 kVA; Winding No. 311; ADS-310; Feature code B599-2
220/380	3	6 leads	6	Winding no. 13; 125°C rise rating 2004 kW / 2505 kVA; stator resistance L-L 0.00102 Ohms; rotor resistance 2.31 Ohms @22°C
240/416	3	6 leads	6	Winding no. 13; 125°C rise rating 2004 kW / 2505 kVA; stator resistance L-L 0.00102 Ohms; rotor resistance 2.31 Ohms @22°C
240/416	3	Wye	12/6	Winding 311/312
254/440	3	6 leads	6	Winding no. 312; 125°C rise rating 2000 kW / 2500 kVA; stator resistance L-L 0.00152 Ohms; rotor resistance 2.31 Ohms @22°C
254/440	3	Wye	12/6	Winding 311/312
266/460	3	Wye	12/6	Winding 311/312
277/480	3	6 leads	6	Winding no. 312; 125°C rise rating 2080 kW / 2600 kVA; stator resistance L-L 0.00152 Ohms; rotor resistance 2.31 Ohms @22°C
277/480	3	Wye	4 Wire	Voltage-277/480, 3 Phase, Wye, 4 Wire
277/480	3	Wye, 4 Wire		Feature code R002-2 Voltage-277/480, 3 Phase, Wye, 4 Wire
280/416	3	Wye		Winding 311; ADS-632; feature code B733-2
346/600	3	6 leads	6	Winding no. 07; 125°C rise rating 2080 kW / 2600 kVA; stator resistance L-L 0.00220 Ohms; rotor resistance 2.31 Ohms @22°C
347/600	3	Wye	6	Winding 07; ADS-309; feature code B720-2
380		Wye		Temp rise 80 degrees C; Duty S; Max surge 3866 kVA; Winding No. 312; ADS-311; Feature code B660-2
380	3	Wye		Winding 311; ADS-632; feature code BC43-2
380	3	Wye, 3-phase	Winding no. 7327	Temp rise 150/125/105 °C; ADS-335; feature code B595; max surge kVA 312
380-480		Wye		Temp rise 125/105 degrees C; Duty S/P; Max surge 2944 kVA; Winding No. 312; ADS-309; Feature code B282-2
400	3	Wye		Winding 312; ADS-310; feature code BC36-2
4160	3	Wye, 3-phase	Winding no. 6307	Temp rise 125/105/80 °C; ADS-324; feature code B467; max surge kVA 51

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 QSK23 family

Part #	Description	Category
AF2559300	Air Cleaner replacement element (Nelson), for Air Cleaner Housing 140-3737	Air filter
501-0876	Line, Fuel Cooler Return (Bearward Cooling System, not shown)	Hose
501-0877	Line, Fuel Supply (Engine Accessories group)	Hose
501-0892	Line, Fuel Cooler Supply (Bearward Cooling System, not shown)	Hose
503-1675	Hose, Reducer (Air Cleaner group)	Hose
503-2754-01	Hose, Oil	Hose
A053A190	Hose, Oil (Valve group)	Hose
140-1548	Indicator, Service	Service part / kit
204-009	Acronyms and Abbreviations	Service part / kit
3822735	Plastic bead blasting media	Service part / kit
4021375	QSK23 Troubleshooting and Repair Manual	Service part / kit
DKE1200BHT	Litho in U.S.A. (17-10)	Service part / kit
EX1200-7	Upperstructure (continued)	Service part / kit
KS-E368R	Head Office	Service part / kit
A059Z452	Seal, O Ring (Valve group)	Seal
A055E534	Switch, Level (low coolant level warning)	Sensor

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 QSK23 series?

The Cummins/Onan QSK23 series engine has an oil capacity of 12.0 liters.

What is the displacement of the Cummins/Onan QSK23 series?

The Cummins/Onan QSK23 series has a displacement of 23.15 liters with 6 cylinders.

Which generators use the Cummins/Onan QSK23 series engine?

The Cummins/Onan QSK23 series powers 11 generator set(s), including Cummins/Onan C750 D6, Cummins/Onan C800 D6, Cummins/Onan CFP23E, Cummins/Onan CFP23E-F10, Cummins/Onan CFP23E-F20.

How often should you change the oil in the Cummins/Onan QSK23 series?

The Cummins/Onan QSK23 series oil change interval is every 250 hours.

What is a common problem with the Cummins/Onan QSK23 series engine?

A commonly reported issue on generators using the Cummins/Onan QSK23 series is: Over Current.