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Cummins/Onan QST30-G5 NR2 Engine

The Cummins/Onan QST30-G5 NR2 is a 30.5 L 12-cylinder turbocharged and low temperature after-cooled engine rated at 1800 rpm, producing up to 1112 kW. It powers generator sets from Cummins/Onan and MQ Power, including the DQFAA, DQFAB, DQFAC and DQFAD. It holds 154 L (40.7 gal) of oil and 167 L (44.1 gal) of coolant.

Also known as: Cummins Inc. QST30-G5 NR2

30.5 L

Displacement

Cylinders

1800 rpm

Rated speed

1112 kW

Gross power

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

Engine specifications

Oil capacity	154.0 L
Coolant capacity	167.0 L
Displacement	30.5 L
Cylinders	12
Aspiration	Turbocharged and low temperature after-cooled
Rated speed	1800 rpm
Gross power	1112 kW

Generator sets powered by this engine

Shared across brands: Cummins/Onan, MQ Power

Cummins/Onan DQFAA Cummins/Onan DQFAB Cummins/Onan DQFAC Cummins/Onan DQFAD MQ Power 1000 kW Containerized Diesel Generator Set MQ Power CG1000C2

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

Common problems

Weak battery warning
Fix: The control system will test the battery each time the genset is signaled to start and indicate a warning if the battery indicates impending failure.
Under frequency shutdown - Genset output frequency cannot be maintained. Settings are adjustable from 2-10 Hz below reference governor set point, for a 5- 20 second time delay. 81
This red lamp is lit when the control detects a Shutdown condition.
Fix: The generator set cannot be started when this lamp is on. After the condition has been corrected, the lamp can be reset by first pressing the Stop button and then the Reset button.
Possible fault with the control or starting system (engine cranks but fails to start). 359
Fix: 1. Check for an empty fuel tank, fuel leaks, or blocked fuel lines and correct as required. 2. Check for a dirty fuel filter and replace if necessary. 3. Check for a dirty or blocked air filter and replace if necessary. 4. Clean and tighten all battery cable connections. 5. Discharged or defective battery. Recharge or replace. 6. Reset the control and restart after correcting the problem.
Overspeed shutdown
Fix: Default setting is 115% of nominal.
Off load running (protection)
Fix: Protects the engine in the event the genset is being called to go off load for too long.
Nature of the fault is an optional customer selection – configurable input #. 1312, 1317, and 1318
Fix: 1. Check the Input # requirements and correct if possible.
Low lube oil pressure warning/shutdown
Fix: Level is preset (configurable with InPower or HMI) to match the capabilities of the engine used. Control includes time delays to prevent nuisance alarms.
Low coolant temperature warning
Fix: Indicates that engine temperature may not be high enough for a 10 second start or proper load acceptance. Can be set up to be a warning or shutdown.
Low Coolant Level input is active. 235
Fix: 1. Look for possible coolant leakage points and repair if necessary. 2. Check the coolant level and replenish if low. 3. Reset the control and restart after locating and correcting the problem.
Low Coolant Level input is active and the threshold response is set to Shutdown. 197
Fix: 1. Look for possible coolant leakage points and repair if necessary 2. Check coolant level and replenish if low. 3. Reset the control and restart after locating and correcting the problem.
Low and high battery voltage warning
Fix: Indicates status of the battery charging system (failure) by continuously monitoring battery voltage.
Low AC voltage shutdown - Voltage on any phase has dropped below a preset value. Adjustable over a range of 50-95% of reference voltage, time delay 2-20 seconds. Default value is 85% for 10 seconds. Function tracks reference voltage. Control does not nuisance trip when voltage varies due to the control directing voltage to drop, such as during a V/Hz roll-off or synchronizing. 27
Local or remote Emergency Stop has been activated. 1433/1434
High lube oil temperature warning/shutdown
Fix: Level is preset (configurable with InPower or HMI) to match the capabilities of the engine used. Control includes time delays to prevent nuisance alarms.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan QST30-G5 NR2.

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Air filter	Dry replaceable element		D041-2		eBay
Fuel filter	30 micron Racor ® fuel filter system		—
Oil filter	Full Pressure 4 Spin-on Full Flow		—
Battery	1800 amps minimum at ambient temperature of -18 °C to 0 °C (0 °F to 32 °F)		—	250 hr
Belt	Belt Driven, Centrifugal		—
Coolant		167.0 L	—	6000 hr
Coolant filter	Not specified		—
Oil		154.0 L	—
Spark plug	Not specified		—

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
Air cleaner restriction indicator	Check	8 hr		Where fitted; if indicator shows red replace elements and reset indicator
Battery connections	Check	8 hr		Connections secure; battery area free from tools and other items
Bedframe/enclosure fluid containment	Drain	8 hr		Where fitted
Control panel operation	Test	8 hr		System performs a control panel test on initial activation
Engine oil level	Check	8 hr		Check with engine stationary; top up to engine specifications
Exhaust components, hardware and condensation trap	Check	8 hr		Drain condensation into a suitable container
Fuel level in tank	Check	8 hr		Add fuel if low; full tank reduces condensation
Fuel lines and hoses	Check	8 hr		Check before starting and again with generator set running
Fuel system primary filter/water separator	Drain	8 hr		Drain one cup or more to remove water and sediment
Generator set enclosure	Check	8 hr		Walk-around inspection; no inlets/outlets covered
Radiator coolant level (water jacket & LTA)	Check	8 hr		Top up with Cummins recommended coolant mix
Charge alternator	Check	50 hr		Check visually and audibly with generator set running
Coolant lines and radiator hoses	Check	50 hr	6 mo	Visually check for leaks, worn or damaged hoses
Cooling fan blades	Inspect	50 hr		Visually through guarding for wear or damage
Crankcase breather tube/collector	Drain	50 hr		Check for condensed oil
Drive belt condition and tension	Check	50 hr		Visually check for evidence of wear or slippage
Engine coolant heater	Check	50 hr		Check heater has power and is running
Battery	Check	100 hr	1 mo	Check electrolyte level at least every month or 100 hours, whichever occurs first
Air cleaner housing	Clean	250 hr	6 mo
Air intake system leaks	Inspect	250 hr	6 mo	Visually and audibly inspect for signs of wear or damage
All hardware (fittings, clamps, fasteners)	Check	250 hr	6 mo
Anti-freeze and DCA concentration	Check	250 hr	6 mo
Battery electrolyte level	Check	250 hr	6 mo
Electrical connections (battery, starter motor and alternator)	Check	250 hr	6 mo
Emergency Stop Button operation	Test	250 hr	6 mo	With generator set running press the Emergency Stop button; check all systems before resetting
Engine ground	Check	250 hr	6 mo	Clean as necessary
Engine mounts	Check	250 hr	6 mo
Engine oil heater	Check	250 hr	6 mo
Engine steam clean	Clean	250 hr	6 mo
Fuel system secondary filter	Replace	250 hr	6 mo
Lubricating oil and filters	Replace	250 hr	6 mo
Radiator air flow	Check	250 hr	6 mo	Inspect radiator through guarding for blockage and debris
Starting motor	Check	250 hr	6 mo
Turbochargers	Check	250 hr	6 mo
Water separator element	Replace	250 hr	6 mo
Aftercooler core	Check	1500 hr	12 mo
Bearings (fan/idler)	Lubricate	1500 hr	12 mo	Re-grease bearings
Coolant filter	Change	1500 hr	12 mo
Coolant heater	Check	1500 hr	12 mo
Fan drive idler arm and fan belt tensioner	Check	1500 hr	12 mo

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
Other	Battery electrolyte specific gravity (fully charged, corrected)	1.260	SG	at 25 °C (77 °F)
Other	Battery electrolyte specific gravity - charge battery if reading is below	1.215	SG	at 25 °C (77 °F)
Other	Compression ratio	14.7:1
Other	Frequency regulation	Isochronous
Other	Generator set operating incline limit	+/- 2.5	degrees
Other	Governor regulation class	ISO 8528 Part 1 Class G3
Other	Specific gravity at end of charge (ambient frequently above 32 °C / 90 °F)	1.240 - 1.260	SG
Other	Specific gravity at end of charge (ambient normally below 32 °C / 90 °F)	1.270 - 1.290	SG
Other	Specific gravity correction	0.007	SG points	subtract for every 10 °C (18 °F) above 25 °C (77 °F); add for every 10 °C below
Other	Specific gravity for filling new cells (ambient frequently above 32 °C / 90 °F)	1.240	SG
Other	Specific gravity for filling new cells (ambient normally below 32 °C / 90 °F)	1.270	SG
Other	Water quality - Calcium, Magnesium (Hardness) maximum level	170	ppm (as CaCO3)
Other	Water quality - Chloride maximum level	40	ppm (as Cl)
Other	Water quality - Sulfate maximum level	100	ppm (as SO4)
Pressure	Fuel transfer pump maximum inlet restriction capability	16	inch Hg
Pressure	Maximum air cleaner restriction	6.2	kPa
Pressure	Maximum cooling air flow static restriction	0.12	kPa
Pressure	Maximum exhaust back pressure	6.8	kPa
Pressure	Maximum fuel inlet restriction	27	kPa
Pressure	Maximum fuel return line restriction	67.5	kPa
Speed	Overspeed limit	2100 ±50	rpm
Speed	Rated speed	1800	rpm
Temperature	Battery temperature fault (fault code 2263) threshold	55	°C (131 °F)
Temperature	Coolant temperature before adding coolant to engine	50	°C (122 °F)	cool to below this value
Temperature	Electrolyte temperature limit for boost charge	43	°C (109 °F)
Temperature	Electrolyte temperature limit for boost charge (tropical climates)	49	°C (120 °F)
Temperature	Maximum fuel inlet temperature	66	°C
Temperature	Maximum jacket water outlet temp (remote radiator cooling)	104	°C
Temperature	Maximum jacket water outlet temp (remote radiator)	104	°C
Temperature	Maximum permissible electrolyte temperature during charge	45	°C (113 °F)
Temperature	Minimum engine water jacket coolant temperature maintained by coolant heaters (standby life safety)	32	°C (90 °F)
Temperature	Temperature below which engine cold sensing logic initiates a warning (Low Coolant Temp)	21	°C (70 °F)
Torque	AC distribution panel 100 A main breaker lugs (#4 to 2/0 conductors, AL or CU)	5.6	Nm (50 in-lbs)
Torque	AC distribution panel ground bar (#1 to 2/0 conductors, AL or CU)	23	Nm (17 ft-lbs)
Torque	AC distribution panel neutral bus (#5 to 300KCMIL conductors, AL or CU)	28.4	Nm (21 ft-lbs)
Voltage	Battery volts limit for boost charge (12 V battery)	15	V
Voltage	Exposure to energized power circuits - significant risk threshold	50 VAC or 75 VDC	V
Voltage	Voltage regulation, no load to full load	± 0.5	%

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	Notes
Coolant	50/50 mixture of fully formulated coolant and DCA4 (or equivalent); premixed fully formulated coolant or 50/50 mix of high-quality distilled/deionized water and fully formulated concentrated antifreeze	Cummins Engineering Standard 14603; Fleetguard coolants containing DCA4 recommended	Either ethylene glycol or propylene glycol; fill to bottom of filler neck
Engine oil	High-quality multi-viscosity lubricating oil such as Cummins Premium Blue or equivalent		Consult authorized distributor for correct lubricating oil specifications for operating conditions
Fuel	ASTM No. 2D diesel fuel, minimum Cetane number 40	ASTM No. 2D; BS 2869:2010+A1:2011 acceptable alternative	Cetane numbers higher than 40 often needed at high altitudes or extremely low ambient temperatures
Fuel	Number 2 diesel		Direct injection; automatic electric fuel shutoff; triple element 10 micron spin-on fuel filters with water separator
Fuel	Number 2 diesel fuel		Direct injection
Fuel	number 2 diesel fuel		Direct injection

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
111	Internal ECM Failure	Internal ECM Failure	Shutdown
1131	Battle Short Active	Control is in Battle Short mode (bypasses several fault shutdowns).	Warning	If possible, investigate any fault codes being bypassed.
115	Eng Crank Sensor Error	Eng Crank Sensor Error	Shutdown
121	Engine Magnetic Crankshaft Speed or Position Lost One of Two Signals	Engine Magnetic Crankshaft Speed or Position Lost One of Two Signals	Warning
1312	Configurable Input # 2	Optional customer configurable input fault.	Info	Check the Input # requirements and correct if possible.
1317	Configurable Input # 13	Optional customer configurable input fault.	Info	Check the Input # requirements and correct if possible.
1318	Configurable Input # 14	Optional customer configurable input fault.	Info	Check the Input # requirements and correct if possible.
141	Low Oil Rifle 1 Pressure	Low Oil Rifle 1 Pressure	Warning	See code 415 procedure.
1416	Fail To Shutdown	Records a bypassed shutdown fault while the generator set was in Battle Short mode.	Warning	Troubleshoot the shutdown fault causing the bypassed shutdown.
142	Oil Overpressure	Oil Overpressure	Warning
143	Low Oil Rifle Pressure	Engine oil pressure has dropped below the warning trip point.	Warning	If powering critical loads and cannot be shut down, wait until next shutdown period, then follow fault code 415 procedure.
1433	Local Emergency Stop	A local Emergency Stop has been activated.	Shutdown	De-activate the Emergency Stop button; press Stop; press Reset; select desired operating mode; check the Emergency Stop button works correctly.
1434	Remote Emergency Stop	A remote Emergency Stop has been activated.	Shutdown	De-activate the Emergency Stop button; press Stop; press Reset; select desired operating mode; check the Emergency Stop button works correctly.
1435	Low Coolant Temperature	Engine coolant heater is not operating or not circulating coolant; occurs when coolant temperature is 21 °C (70 °F) or lower.	Warning	Check coolant heater power supply, blown fuse or disconnected heater cable; look for coolant leaks; check coolant level and replenish.
1438	Fail To Crank	Possible fault with the control, speed sensing, or starting system.	Shutdown	See code 441 for corrective action; ensure the Emergency Stop button is disengaged.
1439	Low Day Tank Fuel Switch	Day tank fuel supply is running low.	Warning	Look for possible fuel leaks and repair; check for low fuel level and replenish.
144	High Coolant 1 Temp	Engine has begun to overheat; coolant temperature has risen to an unacceptable level.	Warning	Review fault code 151 correction list for possible causes.
1441	Low Fuel Level	Fuel level has gone below the threshold setting for low fuel level against the time setting.	Warning	Look for possible fuel leaks and repair; check for low fuel level and replenish.
1442	Weak Battery	During cranking battery voltage is at or below the weak battery warning trip point for a time greater than or equal to the weak battery set time.	Warning	See code 441.
1443	Dead Battery	During cranking battery voltage dropped below the operating voltage of the control, resetting the control; after three consecutive resets this code becomes active.	Shutdown	See code 441.
1444	Overload	Overload	Warning
1445	Short Circuit	Short Circuit	Shutdown
1446	High AC Voltage	High AC Voltage	Shutdown
1447	Low AC Voltage	Low AC Voltage	Shutdown
1448	Under Frequency	Generator set frequency has dropped below 90% of nominal for approximately ten seconds.	Shutdown	Check the fuel supply; check the air intake supply; check the load and correct any overload.
1449	Over Frequency	Generator set frequency has exceeded the Over Frequency threshold for the set time parameter.	Warning	Check the fuel supply; check the air intake supply; check the load and correct any overload.
145	Low Coolant 1 Temp	Engine coolant temperature is below the low coolant temperature warning threshold.	Warning	If powering critical loads and cannot be shut down, wait until next shutdown period, then follow fault code 1435 procedure.
1452	Genset Breaker Fail To Close	Genset Breaker Fail To Close	Warning
1453	Genset Breaker Fail To Open	Genset Breaker Fail To Open	Warning
1455	Utility Breaker Position Contact	Utility Breaker Position Contact	Warning
1456	Bus Out Of Synchronizer Range	Bus Out Of Synchronizer Range	Warning
1457	Fail To Synchronize	Fail To Synchronize	Warning
1459	Reverse Power	Reverse Power	Shutdown
146	Pre-High Engine Coolant Temperature	Engine operating near cooling system capacity.	Warning	Review fault code 151 correction list for possible causes.
1461	Loss of Field (Reverse kVAR)	Loss of Field (Reverse kVAR)	Shutdown
1463	Not In Auto	Not In Auto	Info
1465	Ready To Load	Ready To Load	Info
1469	Speed/Hz Mismatch	Speed/Hz Mismatch	Shutdown
1471	Over Current	Over Current	Warning
1472	Over Current	Over Current	Shutdown
151	High Coolant Temp	Engine has overheated (coolant temperature above shutdown trip point or coolant level is low).	Shutdown	Allow engine to cool completely. Check for coolant leaks and level; check for cooling airflow obstructions; check fan belt; check blower fan and circulation pumps; reset control and restart.
155	High Intake Manf 1 Temp	Engine has overheated (intake manifold temperature above shutdown trip point).	Shutdown	Review fault code 151 correction list for possible causes.
1852	Pre-High H2O In Fuel	Water in the fuel is above normal and has reached the warning trip point.	Warning	Check fuel in tank (local or remote); drain and re-fill if necessary.
196	Low Coolant 1 Level	Engine coolant level has fallen below the trip point.	Warning	Check for coolant leaks and level; replenish if low; reset the control and restart.
197	Low Coolant Level	Engine coolant level has fallen below the trip point.	Warning	Check for coolant leaks and level; replenish if low; reset the control and restart.
1999	Maximum Parallel Time	Maximum Parallel Time	Warning
228	Low Coolant Pressure	Low Coolant Pressure	Shutdown
2335	AC Voltage Sensing Lost (Excitation Fault)	Excitation Fault (Loss of Voltage Sense)	Shutdown	Critical shutdown fault - suspends Battle Short mode.
234	Crankshaft Speed High	Overspeed	Shutdown	Critical shutdown fault - suspends Battle Short mode.
2342	Too Long In Idle	Too Long In Idle	Warning
235	Low Coolant Level	Low Coolant Level input is active and threshold response is set to Shutdown.	Shutdown	Allow engine to cool completely; check for coolant leaks and level; replenish if low; reset control and restart.
236	Both Engine Speed Signals Lost	Both Engine Speed Signals Lost	Shutdown
253	Oil Level Low	Oil Level Low	Shutdown
27	Low AC voltage shutdown	Voltage on any phase dropped below preset value; 50-95% of reference, 2-20 s delay, default 85% for 10 s	Shutdown
2977	Low Coolant 2 Level	Engine coolant level in the second radiator has fallen below the trip point.	Warning	Look for possible coolant leakage points and repair; check coolant level and replenish if low; reset the control and restart.
32	Reverse power shutdown	Adjustment range 5-20% of Standby kW rating, delay 1-15 s; default 10%, 3 s	Shutdown
3416	Start System Fault - Condition Exists	Start System Fault - Condition Exists	Warning	Refer to fault codes 359 and 1438.
359	Fail to Start	Possible fault with the control or starting system (engine cranks but fails to start).	Shutdown	Check fuel tank, leaks or blocked fuel lines; check/replace dirty fuel filter; check/replace dirty air filter; clean and tighten battery cable connections; recharge or replace battery; reset control and restart.
415	Low Oil Rifle Press	Engine oil pressure has dropped below the shutdown trip point.	Shutdown	Check oil level, lines and filters; replenish if low; reset the control and restart.
427	CAN Data Link Degraded	Communication between the engine control (ECM) and the PCC is severed.	Warning	Ensure the E-Stop button is not active; reset the Local/Remote Emergency Stop.
441	Low Battery 1 Voltage	Battery voltage is below 24 VDC and approaching a low level at which unpredictable operation occurs.	Warning	Clean battery terminals and tighten connections; check electrolyte level, top up and recharge; recharge or replace discharged/defective battery.
442	High Battery 1 Voltage	Battery voltage to the control approaching a high level exceeding 32 VDC.	Warning	Clean battery terminals and tighten connections; check battery charge float level and lower if applicable.
46	Negative sequence overcurrent warning	Protects generator from damage due to excessive three-phase load imbalance	Warning
488	High Intake Manf 1 Temp	Engine has overheated (intake manifold temperature above shutdown trip point).	Warning	Review fault code 151 correction list for possible causes.
51	Overcurrent warning/shutdown	Thermal damage curve with instantaneous trip level based on current transformer ratio and application power rating	Shutdown
51G	Ground fault overcurrent	Detects ground fault via external ground fault relay contact input or external CT measurement	Shutdown
59	High AC voltage shutdown	Output voltage on any phase exceeds preset values; 105-125% of nominal, 0.1-10 s delay, default 110% for 10 s	Shutdown
611	Engine Hot Shut Down	An engine hot shutdown has occurred (cooldown timers bypassed).	Warning	Generator set should run at 10% or less load for three minutes before engine shutdown; avoid hot shutdown.
649	Engine Oil Change Needed	Engine Oil Change Needed	Info
781	CAN Data Link Failure	Communication between the engine control (ECM) and the PowerCommand 3.3 control has been severed.	Shutdown	Ensure the E-Stop button is not active; reset the Local/Remote Emergency Stop.
81o	Over frequency shutdown/warning	Genset operating at a potentially damaging frequency; 2-10 Hz above nominal, 1-20 s delay, default 6 Hz 20 s disabled	Warning
81u	Under frequency shutdown	Genset output frequency cannot be maintained; 2-10 Hz below reference, 5-20 s delay, default 6 Hz 10 s	Shutdown

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

Procedures

Battery Charging (Bench / Boost) maintenance

⚠ Batteries should not be left on Boost Charge for extended periods.

Do not put a filled battery into storage without first giving the battery a commissioning charge.
Give batteries a further charge every six months at the normal initial charge rate until voltage ceases to rise.
If the charger has a Boost Charge switch, select Boost at intervals detailed by the battery manufacturer (normally every 6 months).
Reduce the charge rate to normal bench rate if electrolyte temperature exceeds 43 °C (109 °F) or battery volts reach 15 V (12 V battery).
At the end of charging, check electrolyte levels and restore if necessary with electrolyte of correct SG.
Replace vent caps.

Coolant Level - Check maintenance

⚠ Do not open the pressure cap while the engine is running; let the engine cool down and relieve pressure first.

⚠ Do not add cold coolant to a hot engine; allow engine to cool to below 50 °C (122 °F).

Isolate the generator set to prevent accidental starting whilst filling the radiator.
Slowly remove the radiator filler cap.
Coolant level should be level with the bottom of the filler neck.
Slowly fill with a 50/50 mixture of fully formulated coolant and DCA4 until level reaches bottom of filler neck.
Replace the radiator cap securely - push down and twist clockwise until cap lip hits stop flange.
Start the generator set and check for leaks.

Drive Belt - Inspection maintenance

Visually inspect the belt through the guarding.
Check for intersecting cracks (longitudinal cracks intersecting transverse cracks are NOT acceptable).
Check for frays or pieces of material missing.
Check for glazed or cracked side walls and uneven sidewall wear.
Visually inspect sheaves through the guarding for damaged or worn grooves, broken flanges and missing material.
Contact your authorized distributor to have worn belts or sheaves replaced.

Engine Oil Level Check maintenance

⚠ Do not check oil while the generator set is operating; crankcase pressure can blow out hot oil.

Tools: Lint free cloth, Funnel

Remove the dipstick and wipe clean with a lint free cloth.
Fully replace the dipstick.
Remove the dipstick and check oil level against High and Low marks.
Top up to the High mark if necessary with the correct grade of oil.
Remove filler cap, place lint free cloth beneath filler neck, use a funnel to pour oil.
Check oil level with dipstick; do not overfill.
Replace dipstick and oil filler cap.
Remove cloth, start engine, idle five minutes, switch off and wait five minutes.
Check oil level; repeat if oil needs to be added.

Fuel Filter Element Removal maintenance

⚠ Diesel fuel is a fire and explosion hazard; do not permit any open flame or igniter near the fuel system.

Tools: Collar/vent cap wrench

Shut down the engine.
Close the fuel supply shutoff valve.
Place a suitable container under the filter to be replaced.
Use the collar/vent cap wrench to open the vent cap to break the air lock in the filter.
Open the drain valve and allow fuel level to drain below the collar.
Close the drain valve.
Loosen the collar with the collar/vent cap wrench.
Remove the clear cover, filter spring, fuel filter element, and o-ring.
Remove the sealing grommet.
Discard the o-ring and grommet.

Fuel/Water Separator - Drain (Spin on Type) maintenance

⚠ Diesel fuel is a fire and explosion hazard; do not permit any open flame or igniter near the fuel system.

Shut off the engine.
Wait 1 minute to remove any pressure in the fuel line.
Place a suitable container under the fuel filter.
Turn the valve clockwise four complete turns until the valve drops down one inch; drain until clear fuel is visible.
When clear fuel flows, push the valve up and turn counterclockwise to close drain valve.
Before starting the engine, remove the container and clean up any fuel spillage.
Start the engine and check for leaks.

Heavy Duty Air Cleaner Element Installation maintenance

Inspect all seals before installing new air cleaner elements.
Install the Secondary inner air cleaner element first; secure using the inner wing nut with sealing washers.
Install the Primary outer air cleaner element.
Install the end cap and secure using the outer wing nut with sealing washers.
Check for any leaks in the air intake system.

Heavy Duty Air Cleaner Element Removal maintenance

⚠ Cummins does not recommend cleaning paper-type air cleaner elements.

Before disassembly, wipe dirt from the cover and upper portion of the air cleaner.
Remove the outer wing nut and the end cap; sealing washers will need to be re-used.
Remove the Primary outer air cleaner element.
Remove the inner wing nut and remove the Secondary air cleaner element; sealing washers will need to be re-used.

Immobilizing for Safe Working maintenance

⚠ Accidental or remote starting can cause severe personal injury or death.

Tools: Insulated wrench

Press the Off mode switch on the operator panel to shut down the generator set.
Press the Emergency Stop button to prevent starting regardless of start signal source.
Thoroughly ventilate the plant room before disconnecting any leads.
Isolate and lock off the supply to the heater, where fitted.
Isolate and lock off the supply to the battery charger, where fitted.
Isolate the fuel supply to the engine.
Using an insulated wrench, disconnect the negative (-) cable first on the starting and control batteries.
Fit warning notices at each point to indicate Maintenance in Progress.

Normal Duty Air Cleaner Element Installation maintenance

Secure the new air cleaner using the 2 air cleaner housing clamps.
Install the coupler and secure the clamp to the intake tube.
Check for any leaks in the air intake system.

Normal Duty Air Cleaner Element Removal maintenance

⚠ Holes, loose-end seals, dented sealing surfaces, corrosion of pipes and other damage require immediate element replacement.

Before disassembly, wipe dirt from the cover and upper portion of the air cleaner.
Note that normal duty air cleaners do not have serviceable filter elements; the entire cleaner is replaced.
Remove the clamp securing the intake coupler to the air cleaner and slide the coupler off.
Loosen or remove the 2 clamps securing the air cleaner.
Remove the air cleaner from the generator set.

Oil Fill maintenance

⚠ Before carrying out any maintenance, isolate all supplies and disconnect the battery.

Complete lock out procedure to ensure safe working environment.
Refer to Engine Operation & Maintenance Manual for correct oil grade.
Fill the engine to the correct level with clean engine oil.
Check oil level on dipstick; level must be on the high (H) mark. Do not overfill.
Return the generator set to the proper operating conditions.
Operate the generator set at idle speed and check for leaks.
Shut down the generator set.
Wait approximately 5 minutes to allow oil to drain from upper parts of engine.
Rectify any leaks; check the oil level; add oil as necessary to reach H mark.
Dispose of waste material in accordance with local regulations.

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
110/190-139/240		12-lead	12-lead	Temp rise 125/105; winding no. 770; alternator data sheet ADS-310; feature code B258
120/208	3	Wye	12/6	Winding 311/312
120/208-139/240		12-lead	12-lead	Temp rise 125/105; winding no. 774; alternator data sheet ADS-310; feature code B252
120/208-139/240	3	12-lead	12	Temp rise 125/105 °C; ADS-312; feature B252
120/240	3	Delta	12/6	Winding 311/312
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
210/380-277/480	3	Wye, 3-phase	6 (12 optional)	ADS-331; feature B284
220/380-277/480		12-lead	12-lead	Temp rise 125/105; winding no. 770; alternator data sheet ADS-310; feature code B258
220/380-277/480	3	Wye, 3-phase	Wye, 3-phase	Temp rise 125/105; winding no. 770; alternator data sheet ADS-310; feature code B282
240/416	3	Wye	12/6	Winding 311/312
240/416-277/480		12-lead	12-lead	Temp rise 125/105; winding no. 774; alternator data sheet ADS-310; feature code B252
240/416-277/480	3	12-lead	12	Temp rise 125/105 °C; ADS-312; feature B252
254/440	3	Wye	12/6	Winding 311/312
266/460	3	Wye	12/6	Winding 311/312
277/480		12-lead	12-lead	Temp rise 125/105; winding no. 772; alternator data sheet ADS-309; feature code B246
277/480	3	Wye, 3-phase	Wye, 3-phase	Temp rise 125/105; winding no. 772; alternator data sheet ADS-309; feature code B276
277/480	3	Wye, 4 wire	12/6	Winding 311/312; feature code R002-2
347/600	3	3-phase	6	ADS-311 / ADS-312 / ADS-330; features B300/B301/B604
347/600	3	Wye	6	Winding 07
347/600	3	Wye, 3-phase	Wye, 3-phase	Temp rise 125/105; winding no. 772; alternator data sheet ADS-309; feature code B300

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

Common questions

What is the oil capacity of the Cummins/Onan QST30-G5 NR2?

The Cummins/Onan QST30-G5 NR2 engine has an oil capacity of 154.0 liters.

What is the displacement of the Cummins/Onan QST30-G5 NR2?

The Cummins/Onan QST30-G5 NR2 has a displacement of 30.5 liters with 12 cylinders.

Which generators use the Cummins/Onan QST30-G5 NR2 engine?

The Cummins/Onan QST30-G5 NR2 powers 6 generator set(s), including Cummins/Onan DQFAA, Cummins/Onan DQFAB, Cummins/Onan DQFAC, Cummins/Onan DQFAD, MQ Power 1000 kW Containerized Diesel Generator Set.

What is a common problem with the Cummins/Onan QST30-G5 NR2 engine?

A commonly reported issue on generators using the Cummins/Onan QST30-G5 NR2 is: Weak battery warning. Fix: The control system will test the battery each time the genset is signaled to start and indicate a warning if the battery indicates impending failure..