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Cummins/Onan QSX15-G8 Engine

Name: Cummins/Onan QSX15-G8 Engine
Brand: Cummins/Onan

The Cummins/Onan QSX15-G8 is a turbocharged with air-to-air charge air cooling engine rated at 1500 rpm. It powers generator sets from Cummins/Onan, including the 352DFEH and DFE. It holds 83.3 L (22.0 gal) of oil.

Also known as: Cummins QSX15-G8

Part of the Cummins/Onan QSX15 engine family — 7 variants share parts & fitment.

1500 rpm

Rated speed

83.3 L

Oil capacity

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

Engine specifications

Oil capacity	83.3 L
Aspiration	Turbocharged with air-to-air charge air cooling
Rated speed	1500 rpm

Generator sets powered by this engine

Cummins/Onan 352DFEH Cummins/Onan DFE

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

Common problems

Over Current 1471
Low AC Voltage 2331
High AC Voltage 2358
Weak Battery 1442
Warning, Shutdown, and Non-Automatic lamps are not lit. Digital display shows main menu or selected menu.
Cause: Indicates all engine systems are normal. No corrective action required
Warning Status Indicator: This yellow lamp is lit whenever the control detects a warning condition.
Fix: After the condition is corrected, warning indicators can be reset by pressing the Fault Acknowledge button. (It is not necessary to stop the generator set if the fault becomes inactive during genset operation.)
Warning lamp lights.
Cause: LOW COOLANT TEMP 210 – WARNING
Fix: Set is in standby mode but is not operating. Warning occurs when engine coolant temperature is 70° F (21° C) or lower. NOTE: In applications where the ambient temperature falls below 40°F (4°C), Low Engine Temp may be indicated even though the coolant heaters are operating.
Under Frequency 1448
Too Long in Idle 2342
The light will display the fault codes (active or inactive) in succession, starting with the most recent. Up to 32 (unacknowledged) fault codes can be stored in control panel memory. 213
Speed/Hz Match 1469
Speed Signal Lost 121
Shutdown Status Indicator: This red lamp is lit whenever the control detects a shutdown condition. The generator set can not be started when this lamp is on.
Fix: After the condition is corrected, shutdown indicators can be reset by turning the 0/Manual/Auto switch to the 0 position, and pressing the Fault Acknowledge button.
Shutdown lamp lights. 212
Cause: Indicates engine has overheated (coolant temperature has risen above the shutdown trip point: 223° F – standby / 215° F – primary) or the coolant level is low. Allow engine to cool down completely before proceeding with the following checks:
Fix: A. Check coolant level and replenish if low. Look for coolant leakage and repair if necessary. b. Check for obstructions to cooling airflow and correct as necessary. c. Check fan belt and repair or tighten if necessary. d. Reset control and restart after locating and correcting problem. Contact an authorized service center if none of the above.
Shutdown After Battle Short 1123

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan QSX15-G8.

Service intervals

Item	Action	Hours	Months	Notes
Air cleaner	Check	250 hr	6 mo	X1; replace as necessary; refer to QSX15 engine manual
All hardware (fittings, clamps, fasteners, etc.)	Check	100 hr		Daily or after 8 hours
Anti-freeze and DCA concentration	Check	250 hr	6 mo	X1; refer to QSX15 engine manual
Coolant heater(s)	Check	100 hr		Daily or after 8 hours
Drive belt	Check	250 hr	6 mo	X1; refer to Cummins QSX15 Series Engine Operation and Maintenance Manual for interval/procedure
Engine oil level	Check	8 hr		Daily or after 8 hours
Fuel filter(s)	Drain	250 hr	6 mo	X1; refer to QSX15 engine manual
Genset	Inspect	8 hr		Daily; check for oil, fuel, cooling and exhaust system leaks
Radiator hoses for wear and cracks	Check	250 hr		Daily or after 8 hours
Charge Air Piping	Check	50 hr		Weekly
Coolant heater	Check	50 hr		Weekly or after 50 hours
Coolant level	Check	50 hr		Weekly or after 50 hours
Exhaust condensate trap	Drain	100 hr		Drain water to prevent it flowing back into the engine
Fuel level	Check	50 hr		Weekly or after 50 hours
Oil level	Check	50 hr		Weekly or after 50 hours
Air cleaner	Clean	100 hr		Monthly or after 100 hours; clean if required, perform more often in dusty conditions
Battery charging system	Check	100 hr		Monthly or after 100 hours
Battery electrolyte level	Check	200 hr		Monthly or After 100 Hrs
Fuel tank water and sediment	Drain	100 hr		Monthly or after 100 hours
General set inspection	Inspect	100 hr		Monthly or after 100 hours (Table 5-1, footnote X2): check for oil, fuel, cooling and exhaust system leaks; check exhaust system audibly and visually with set running
Generator air outlet	Check	100 hr		Monthly or After 100 Hrs
Radiator hoses	Check	500 hr	12 mo	Monthly or After 100 Hrs; check for wear and cracks
Starting batteries	Check	100 hr		Check condition and terminals
Air cleaner	Replace	250 hr		Check air cleaner; replace as necessary. Refer to QSX15 manual.
Crankcase oil and filter	Change	250 hr	12 mo	Prime power: every 6 months or 250 hours; standby: every 12 months or 250 hours, whichever comes first
Drive belt tension	Check	250 hr	6 mo	Visually check belt for wear or slippage; replace if hard or brittle
Engine oil and filter	Replace	250 hr	6 mo	X1; 6 Months or After 250 Hrs; refer to QSX15 engine manual
Radiator Hoses	Inspect	250 hr	6 mo	Check for wear & cracks
Water coolant filter	Replace	250 hr	6 mo	X1; 6 Months or After 250 Hrs
Air cleaner element	Change	500 hr	12 mo	Yearly or after 500 hours; clean if required more often
Coolant filter	Change	500 hr	12 mo	Yearly or after 500 hours; refer to engine operation and maintenance manual
Cooling system	Clean	500 hr	12 mo	Yearly or after 500 hours; drain and replace coolant mixture
Crankcase breather	Clean	500 hr	12 mo	Yearly or after 500 hours
Engine oil and filter	Change	500 hr	12 mo	Table 5-1, footnote X1
Fuel filter	Change	500 hr	12 mo	Table 5-1, footnote X1
Fuel filters	Change	500 hr	12 mo	Yearly or after 500 hours
Generator insulation resistance	Test	500 hr	12 mo	Follow periodically throughout life of set or if generator has set idle with no heaters; contact authorized service center
Water coolant filter	Change	500 hr	12 mo	Table 5-1, footnote X1
Cooling systems	Clean	500 hr	12 mo	X1; 1 Year
Fuel filter	Replace		12 mo	X1; 1 Year

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	Exhaust pipe clearance from combustible wall or partition	12	inches (305 mm)	minimum
Clearance	Exhaust pipe clearance to combustible wall/partition	12	inches (305 mm)
Clearance	Float switch assembly float lift clearance below C-clip stop	1/8	inch (3 mm)	use a feeler gauge
Clearance	Fuel line clearance from electrical wiring	1/2	inch (12.7 mm)
Clearance	Fuel line clearance from hot exhaust parts	2	inch (51 mm)
Clearance	Generator mount pre-load steel spacer thickness	1 3/4	inch	two spacers under both stator foot brackets
Clearance	Generator-to-engine angular alignment (T.I.R.)	.001 in. per inch of radius (center of shaft to indicator axis), maximum	in	750 kW gensets and larger
Clearance	MPU installation gap adjustment	back out 1/4 turn after touching gear tooth	turn
Clearance	Vibration isolator base elevation difference	0.25	inch (6 mm)	shimmed or grouted within this of each other
Clearance	Vibration isolator clearance	0.25	inch (6 mm)
Clearance	Vibration isolator nominal clearance (leveling bolt)	0.25	inch (6 mm)	minimum, or greater
Gap	Coolant level below radiator cap lower sealing surface	3/4 inch (18 mm)	inch (mm)
Other	AVR Droop setting	5	% at full load, 0 PF
Other	AVR voltage regulation (load regulation)	approximately ±0.5	% RMS
Other	Ambient temperature below which coolant heaters recommended (NFPA 110)	40	°F
Other	Battery CCA (minimum)	1400	CCA	Cold Soak @ 0° F (-18° C)
Other	Battery specific gravity (fully charged)	1.26	specific gravity	at 80 F (27 C)
Other	Battery specific gravity (high ambient, above 95F/35C)	1.225		recommended to reduce electrolyte loss
Other	Battery specific gravity (recharge threshold)	below 1.260
Other	Battery specific gravity charge threshold	1.215	corrected	charge battery if reading below
Other	Battery specific gravity fully charged	1.260	corrected	add 0.004 per 10 F above 80 F (27 C)
Other	Battery terminal cleaning solution	1/4 pound baking soda to 1 quart water
Other	CAN datalink main trunk maximum length	40	meters	no more than 30 devices
Other	CAN datalink stub maximum length	1	meter	stub from main trunk to each module
Other	CAN datalink transmission speed	250	KBaud
Other	Charge battery if specific gravity below	1.215	specific gravity
Other	Fully charged battery corrected specific gravity	1.260	specific gravity	corrected reading @ 80 F (27 C)
Other	GOV GAIN default value for paralleling applications	70	%
Other	Mounting bolt size	5/8	inch or 16 mm
Other	Mounting bolts	5/8 inch or 16 mm	inch / mm	anchored mounting bolts
Other	Output frequency adjustment (PCC)	+/- 5	%	set running under normal parameters
Other	Over current warning threshold	110	% of rated
Other	Over/Under Frequency Sensor Module - Over Hz Set, 50 Hz nominal	55	Hz	reset 53 Hz
Other	Over/Under Frequency Sensor Module - Over Hz Set, 60 Hz nominal	65	Hz	reset 63 Hz
Other	Over/Under Frequency Sensor Module - Under Hz Set, 50 Hz nominal	45	Hz	reset 47 Hz
Other	Over/Under Frequency Sensor Module - Under Hz Set, 60 Hz nominal	55	Hz	reset 57 Hz
Other	Over/Under Voltage Sensor Module time delay	typically 25 percent, approximately 2.5	seconds
Other	Overcrank cranking limit	75	seconds	three 15-second cranking cycles with two 15-second rest periods
Other	REG VHZ (underfrequency roll-off) adjustable range	1 through 50; normal range 7 through 21
Other	Short circuit shutdown threshold	175	% of rated current
Other	Specific gravity correction	0.004	gravity point per 10 F above 80 F (27 C)
Other	Start delay adjustment range	0 to 300	seconds
Other	Start delay adjustment range (PCC)	0 to 300	seconds	Auto mode remote starting
Other	Stop delay adjustment range	0 to 600	seconds
Other	Stop delay adjustment range (PCC)	0 to 600	seconds	Auto mode remote stopping
Other	Under Frequency Roll Off (UFRO) knee point, 50 Hz units	48 to 49	Hz
Other	Under Frequency Roll Off (UFRO) knee point, 60 Hz units	58 to 59	Hz
Pressure	Air cleaner element cleaning compressed air pressure	30	psi (207 kPa)	nozzle held at least 1 inch (25 mm) away
Pressure	Engine oil pressure (displayed example)	75	PSI
Pressure	Engine oil pressure - K19 normal	50-70	psi (345-482 kPa)	run mode
Pressure	Engine oil pressure - K38 normal	45-65	psi (310-448 kPa)	run mode
Pressure	Engine oil pressure - K50 normal	50-70	psi (345-482 kPa)	run mode
Pressure	Engine oil pressure - L10/M11 normal	30-50	psi (207-345 kPa)	run mode
Pressure	Engine oil pressure - NTA 855 normal	35-50	psi (241-345 kPa)	run mode
Pressure	Engine oil pressure - V28 normal	50-90	psi (345-620 kPa)	run mode
Pressure	Engine oil pressure shutdown limit - L10/M11	20	psi (138 kPa)	run mode value
Pressure	Engine oil pressure shutdown limit - L10/M11	8	psi (55 kPa)	idle mode value
Pressure	Engine oil pressure warning limit - L10/M11	12	psi (83 kPa)	idle mode value
Pressure	Engine oil pressure warning limit - L10/M11	25	psi (172 kPa)	run mode value
Pressure	Fuel transfer pump maximum inlet restriction capability	16	inch Hg	approximately equivalent to 20 feet of diesel

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		Refer to Cummins QSX15 Series Engines Operation and Maintenance Manual for coolant recommendations/specifications		58.0 L	Cooling System (Capacity Std. Radiator) printed as 15.3 Gal (58 L); check anti-freeze and DCA concentration
Coolant	Balanced coolant mixture of water and antifreeze	Refer to Cummins engine Operation and Maintenance Manual		90.0 L	Capacity with standard radiator 24 Gal (90 L); drain and replace mixture every year or after 500 hours; add until 3/4 inch (18 mm) below radiator cap lower sealing surface
Coolant	soft water / E.G. / DCA mixture				Cooling system to be filled with soft water/E.G./DCA mixture (on-site review checklist).
Engine oil		Refer to Cummins QSX15 Series Engines Operation and Maintenance Manual for lubricating oil classification/viscosity		58.0 L	Oil Cap. w/Filters printed as 26 Gallons (58 L); gense is shipped filled with correct type and quantity of oil
Fuel	ASTM No. 2 diesel				Cummins engines normally use ASTM No. 2 diesel fuel.
Fuel	Diesel				Day tank fuel transfer pump maintains reservoir of diesel fuel in the day tank.
Fuel	diesel				Refer to Cummins QSX15 Series Engines Operation and Maintenance Manual for fuel recommendations; do not use zinc coated or copper fuel lines with diesel fuel; keep fuel supply tanks as full as possible
Grease	Lithium based grease, Mobilux No. 2 or Shell Alvania R3		-30°C to 120°C	2.74 oz (81 ml)	End bearing lubricant; grease equally divided between bearing, bearing cap cavity and bearing cartridge cavity.
Other	Donaldsons D1400 solvent				Soak air cleaner filter element at least 15 minutes in water and D1400 solvent to remove soot, carbon and dirt

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
101	IDLE MODE	Indicates that the engine is operating in idle mode. Grounding the engine idle input causes generator build-up to be inhibited and the engine to be governed at 800 RPM.	Warning	Remove ground from engine idle input to return to normal speed and voltage.
102	EMERGENCY STOP	Local or remote Emergency Stop; engine shuts down and will not crank	Shutdown	Turn the switch clockwise and allow it to pop out (local only). Move the Run/Off/Auto switch to Off. Press the Reset switch. Select Run or Auto, as required.
111	Internal ECM error	Internal ECM error	Shutdown
1118		Prelube relay driver	Warning
112	Actuator not responding	Category A	Shutdown
1121		Failed to Disconnect	Warning
1122	Rated/Idle Trans		Info
1123	Shutdown After Battle Short	A shutdown fault occurred while Battle Short was enabled and Battle Short transitioned from enabled to disabled	Warning	Review the Fault History and perform corrective action
1124	Delayed Shutdown	Provides advanced warning of an impending generator set shutdown to loads which cannot handle sudden power loss	Warning	A shutdown fault is present; review fault history
113	Actuator sensor fault	Category B	Warning
1131	Battle Short Active	Battle short mode has been activated	Warning	Battle short function enabled
115	No speed signal	No speed signal	Shutdown
116	Time press sensor high	Time press sensor high	Shutdown
117	Time press sensor low	Time press sensor low	Shutdown
118	Pump press sensor high	Pump press sensor high	Warning
119	Pump press sensor low	Pump press sensor low	Warning
121	Speed Signal Lost	No engine speed signal	Warning
1219		Utility CB tripped	Warning
122	Manifold air press sensor	Manifold air press sensor	Warning
1222		Power transfer not in auto	Warning
1223		Utility frequency sensor	Warning
1224		Gen over voltage sensor	Warning
1225		Gen under voltage sensor	Warning
1226		genset frequency sensor	Warning
123	Manifold air press sensor	Manifold air press sensor	Warning
1245	CAN - Engine Shutdown	The PCC received a shutdown message from the ECM	Shutdown	Refer to the E-Controls service tool and the engine service manual
1246	CAN - Unknown Engine Fault	The PCC received an unknown message from the ECM	Warning	Refer to the E-Controls service tool and the engine service manual
1247	CAN - Engine Unannounced Fault	The PCC received an unknown message from the ECM	Warning	Refer to the E-Controls service tool and the engine service manual
1248	CAN - Engine Warning Fault	The PCC received an unknown message from the ECM	Warning	Refer to the E-Controls service tool and the engine service manual
1311	Customer input #1	Optional customer-selected fault, e.g. Low Fuel Day Tank, Water In Fuel, Ground Fault, Low Starting Hydraulic/Air Pressure		Programmable via service tool: enable/disable, status/warning/shutdown, active closed/open, custom display name
1311, 1312, 1317, 1318	Customer Input	Nature of the fault is an optional customer selection		Disconnect signal lead from TB1 (CUST_IN1 TB1-4, CUST_IN2 TB1-5, CUST_IN3 TB1-6, CUST_IN4 TB1-7) and reset the control; if the message clears, external wiring has a short/open or the active input selection (closed/open) is not correct
1312	Customer input #2	Optional customer-selected fault		Customer defined fault; message editable by the customer; can be programmed to initiate a shutdown or warning.
1313	Network Fault 1 thru 4	Network Fault 1		Customer defined fault; message editable by the customer; can be programmed to initiate a shutdown or warning.
1313-1316	Network Fault 1 Through 4	Indicates network input (#1-#4) is in an active state		Each fault function can be programmed (using the service tool) as Status, Warning, or Shutdown; change display name using up to 19 characters
1314	Network Fault 2	Network Fault 2		Customer defined fault; message editable by the customer; can be programmed to initiate a shutdown or warning.
1315	Network Fault 3	Network Fault 3		Customer defined fault; message editable by the customer; can be programmed to initiate a shutdown or warning.
1316	Network Fault 4	Network Fault 4		Customer defined fault; message editable by the customer; can be programmed to initiate a shutdown or warning.
1317	Customer input #3	Customer input #3		Customer defined fault; message editable by the customer; can be programmed to initiate a shutdown or warning.
1318	Customer input #4	Customer input #4		Customer defined fault; message editable by the customer; can be programmed to initiate a shutdown or warning.
1319	High alternator temp	High alternator temp	Warning
1321	Common warning driver	Common warning driver	Warning
1322	Load gov kW setpoint oor hi	Load gov kW setpoint oor hi	Shutdown
1323	Load gov kW setpoint oor lo	Load gov kW setpoint oor lo	Shutdown
1324	Load gov kVAR oor hi	Load gov kVAR oor hi	Warning
1325	Load gov kVAR oor lo	Load gov kVAR oor lo	Warning
1326	Backup starter disconnect	Category B	Warning
1327	Load gov kW analog oor	Load gov kW analog oor	Shutdown
1328	Genset CB tripped	Genset CB tripped	Warning
1329	AVR DC power failure	Category B	Warning
1331	AVR driver shorted	Category A	Shutdown
1332	Manual switch oor lo	Manual switch oor lo	Shutdown
1333	Manual switch oor hi	Manual switch oor hi	Shutdown
1334	Critical scaler oor	Critical scaler oor	Shutdown	Correct the feature/calibration entered into the control
1335	Noncrit Scaler Out Of Range	Non critical scaler oor	Warning	Correct the feature/calibration entered into the control
1336	Cooldown complete	Cooldown complete	Shutdown
1337	No Message	Network wink	Info
1341	Load demand stop	Load demand stop	Shutdown
1342	Slot 0 card	Slot 0 card	Shutdown
1343	Slot 1 card	Slot 1 card	Shutdown
1344	Slot 2 card	Category A	Shutdown
1345	Slot 3 card	Slot 3 card	Shutdown
1346	Slot 4 incorrect	Slot 4 incorrect	Shutdown
1347	Slot 5 card	Category A	Shutdown
1348	Slot 6 card	Category A	Shutdown
1349	Slot 7 card	Category A	Shutdown
135	Oil pressure sensor	Oil pressure sensor	Warning	Verify fault simulation not enabled (InPower); inspect sensor and engine harness connector pins; use oil pressure sensor simulator to check control response, replace sensor if it responds; check P7-13, 17, 21 for short (>200k ohms OK) and open (10 ohms or less OK)
1351	Slot 4 / network enabled	Slot 4 / network enabled	Warning
141	Oil pressure sensor	Oil pressure sensor	Warning	Verify fault simulation not enabled; inspect sensor/harness connector pins; use simulator to check control response; check P7-13, 17, 21 short/open
1414	Run relay contact	Run relay contact	Warning
1415	Run relay driver	Run relay driver	Warning
1416	Fail to shutdown	Fail to shutdown	Warning	Status - indicates the Fault Bypass mode is enabled (used primarily by service personnel for troubleshooting). The genset ignores the majority of system shutdown faults.
1417	Powr Down Error	The control has failed to go to sleep	Warning	Possible base board fault
1419	Fuel rail driver	Fuel rail driver	Warning
1421	Timing rail driver #1	Timing rail driver #1	Warning
1422	Timing rail driver #2	Timing rail driver #2	Warning
1424	High side driver	High side driver	Warning
1427	Overspeed relay driver	Overspeed relay driver	Warning
1428	LOP shutdown relay driver	LOP shutdown relay driver	Warning
143	Pre-Low Oil Pressure	Low oil pressure	Warning	Verify fault simulation not enabled; check oil level, lines and filters; use oil pressure sensor simulator; check +5 VDC at sensor (E1-A) and at P7-21; use simulator to P7-13 (OP OUT) and P7-17 (OP COMM); isolate to harness or base board
1433	Emergency stop - local	Local Emergency Stop	Shutdown	Pull the Emergency stop button out; move the O/Manual/Auto switch to O; press the front panel Fault Acknowledge/Reset button; select Manual or Auto as required

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

Procedures

Aligning Generator with Engine (Angular Alignment) adjustment

⚠ Accidental starting of the generator set during this procedure presents the hazard of severe personal injury or death.

Tools: Dial indicator, Shims

Disconnect the negative (-) battery cable(s) before beginning.
Fasten a dial indicator to the generator shaft or cooling fan with the sensing point on the capscrew head or flat surface of the drive disc at the bolt circle diameter.
Bar the engine over in a clockwise rotation as viewed from engine flywheel; do not allow it to roll back on compression.
Determine the total indicator reading (T.I.R.) as the sum of the maximum positive and negative dial indicator readings over one revolution.
Measure the distance from the center of the generator shaft to the indicator measuring point.
Measure the distance from the generator side of the flex discs to the center of the generator mounting bolt.
Compare the distances; multiply this ratio times one half the T.I.R. to approximate the amount of shims to remove or add.

Angular Alignment Procedure (Generator to Engine) adjustment

⚠ Accidental starting during this procedure presents the hazard of severe personal injury or death.

⚠ Do not bar engine over by prying on fan blade.

Tools: dial indicator

Disconnect the negative (-) battery cable(s) before beginning.
Fasten a dial indicator to the generator shaft or cooling fan with sensing point resting on the drive disc capscrew head/flat surface at the bolt circle diameter.
Bar the engine over in a clockwise rotation as viewed from the engine flywheel; do not allow it to roll back on compression at the end of travel of each reading.
Record the total indicator reading (T.I.R.) as the sum of the maximum positive and negative dial indicator readings over one engine revolution.
Compare the measured T.I.R. to the maximum allowed (.001 in. per inch of radius from center of shaft to indicator axis); add or remove shims under the generator mounting feet to correct.

Axial Alignment Procedure adjustment

Tools: dial indicator holding device with magnetic base or clamp

Fasten dial indicator holding device to skid base, engine block, or generator shell with a magnetic base or clamp.
Position so the sensor point of the indicator rests on the generator shaft hub.
Bar the engine over in a clockwise rotation through a couple of rotations.
Record indicator readings in eight equally spaced points around the shaft diameter.
To correct out-of-tolerance T.I.R., remove the capscrews connecting drive discs and flywheel.
Mark the drive discs and flywheel with respect to each other and rotate either the engine or generator so drive disc holes are repositioned 180 degrees from original location.
Reinstall the drive disc capscrews and retorque; recheck shaft alignment. If unchanged, rotate discs 30, 60, or 90 degrees from original location.

Axial Alignment Procedure (Generator to Engine) adjustment

Tools: dial indicator

Fasten a dial indicator holding device to the skid base, engine block, or generator shell with the sensor point resting on the generator shaft hub.
Bar the engine over in a clockwise rotation through a couple of rotations, recording indicator readings at eight equally spaced points around the shaft diameter to obtain axial T.I.R.
Reduce the measured T.I.R. runout by one half if excessive vibration remains after angular alignment.

Generator Mount Pre-Load Adjustment adjustment

⚠ Accidental starting of the generator set during this procedure presents the hazard of severe personal injury or death.

Tools: two 1 3/4 inch T x 2 inch W x 6 inch L steel spacers, adequate lifting device

Turn off and disconnect battery charger (if equipped).
Disconnect the negative (-) battery cable(s) to prevent accidental starting.
Unscrew bolt (Item 2) from skid but do not remove it from either rear engine vibration isolator.
Loosen the three screws that secure the engine mount brackets to the engine.
Loosen but do not remove the hex nut (Item 1) from the M20 screw of the generator vibration isolators.
Lift the generator until the mounting feet brackets are high enough to insert a 1 3/4 inch steel spacer under both stator foot brackets.
Insert spacers and lower the generator so the full weight rests on the mounting foot brackets.
Make sure no gap is present between the skid and the lower mount of the rear engine vibration isolators; tighten the three screws to 190-200 ft-lbs.
Lift the generator to remove the two 1 3/4 inch steel spacers.
Before lowering, start the threads of the rear engine vibration isolator bolts (Item 2).
Lower the generator and tighten the two rear engine vibration isolator bolts to 270-330 ft-lbs.
Secure the generator foot brackets to the vibration isolators; tighten the fastener to 270-330 ft-lbs.

Bus Voltage Calibration (C) diagnostic

Tools: calibrated voltmeter

Display the Bus Voltage Calibration submenu.
With all gensets OFF, attach a calibrated voltmeter to TB1-A (L1) and TB1-B (L2) of the bus PT module.
Start another genset and allow it to reach normal operating speed and voltage. Connect to the bus.
Calibrate the voltage reading for Bus Volts L1 so the display matches the calibrated meter.
Shut the generator set OFF.
Repeat steps 2 through 5 for Bus Volts L2 and L3.
Exit menu to save changes.

Engine Does Not Crank in Manual Mode - Diagnosis and Repair diagnostic

⚠ Accidental starting can cause severe personal injury or death; disconnect negative (-) battery cable with insulated wrench.

⚠ Set generator set to off mode before disconnecting/connecting harness connectors.

Tools: True RMS meter, Insulated wrench, Jumper leads

Verify power to control: Control Alive indicator should be flashing on base board.
Clean battery cable terminals and tighten connections using an insulated wrench.
Remove F4 and check continuity; if open, replace with same type/amp rating (5 Amps).
If F4 OK, remove connector P7 and check B+ at P7-1 to P7-4 and GND at P7-5 to P7-8.
If B+/ground missing, isolate to harness and TB BAT terminal on engine block.
If B+ and ground OK, base board may be defective; cycle power by reconnecting P7.
Confirm calibration part number matches serial plate; re-enter calibration file if needed.
With E-Stop not activated, remove P1 and check continuity between P1-1 (ESTOP-NC1) and P1-2 (ESTOP-NC2).
With S12 in Manual, remove P1 and check continuity from P1-6 (MAN) to P1-9 (GND).
Remove P3 and check continuity from P3-9 (MAN RUN/STOP) to P3-10 (GND); if none when pressing button, replace front membrane panel.

Generator/PCC Control Isolation Procedure diagnostic

⚠ HIGH VOLTAGE. Touching uninsulated high voltage parts inside the control box can result in severe personal injury or death.

Tools: Voltmeter, Jumpers, 12 volt battery

Throw the line circuit breaker OFF and shut down the set.
Remove accessory box cover; remove plug P10 from A37 J10.
Prepare to measure output voltage across generator terminals.
Connect 12V battery jumpers to X (P10-6 red) and XX (P10-3 brown).
Check polarity; incorrect polarity makes the test inconclusive.
Start set and connect battery negative to the XX lead.
Rated or higher balanced voltage means generator circuitry is OK.
Unbalanced voltage: troubleshoot main stator; low voltage: exciter/field.

Genset Ammeter Display Calibration (B) diagnostic

Tools: calibrated ammeter

Display the Current Calibration submenu.
With the genset OFF, attach a calibrated ammeter to L1.
Start the genset and allow it to reach normal operating speed.
Load the genset to maximum rated kVA at rated voltage.
Calibrate the reading for L1 current so the display agrees with the calibrated ammeter.
Repeat steps 2 through 5 for L2 and L3.
Exit menu to save changes.

Genset Voltage Display Calibration (A) diagnostic

⚠ Contacting high voltage components can cause electrocution, resulting in severe personal injury or death.

Tools: calibrated RMS multimeter (Fluke 87 or 8060A recommended)

Display the Voltage Calibration submenu.
With the genset OFF, attach a calibrated voltmeter to the AC output from L1 to L2.
Start the genset and allow it to reach normal operating speed.
Calibrate voltage reading for L1 so the display agrees with the calibrated voltmeter.
Shut the generator set OFF.
Repeat steps 2 through 5 for L2 and L3.
Exit menu to save changes.

Insulation Resistance (Megger) & Polarization Index (PI) Testing diagnostic

⚠ The windings of medium-voltage (601 through 15,000 volts) generator sets must be dry before the generator is operated.

Tools: Megger or insulation resistance meter, Grounding cluster, High voltage gloves

Perform the Generator Set Grounding Procedure.
Disconnect plug J10 from A37 and AC control leads 4,5,6,7,8.
If RTD option installed, ground all six RTD temperature leads (18 leads).
Perform Insulation Resistance Test and PI Test for desired windings.
Megger test: apply voltage for up to one minute.
PI test: apply voltage for ten minutes; record 1-minute and 10-minute readings.
PI ratio of 2 or greater is good for new and in-service sets.
Investigate and correct low readings before returning set to service.

Megger and PI Test diagnostic

⚠ Medium-voltage (601 to 15,000 volts) windings must be dry before the generator is operated.

Tools: Megger or Insulation Resistance Meter, Wheatstone bridge or digital ohmmeter, Grounding Cluster

Perform the Generator Set Grounding Procedure.
Disconnect plug J10 from the voltage regulator output module and the AC control leads (marked 4, 5, 6, 7, 8).
If RTD option installed, ground all six RTD temperature leads (18 leads total).
Perform the Winding Resistance Test for the desired windings.
Perform the Insulation Resistance (Megger) Test and PI Test for the desired windings.
Megger test: apply voltage for up to one minute.
PI test: apply voltage for ten minutes; record resistance at one minute and ten minutes.
PI is the ten-minute reading divided by the one-minute reading; ratio of two or greater is good.

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

Phase	Connection	Leads	Notes
	12 lead generator sets	Load wires are routed through the CTs	Reconnectable gensets (12 leads) have dual secondary CTs (3 pins); CT wire 2/3 to pin 2 (high voltage) or pin 3 (low voltage).
	6 lead generator sets	Generator output leads are routed through the CTs	Non-reconnectable gensets (6 leads) have single secondary CTs (2 pins).
	Cummins PowerCommand generic AC Reconnect Wiring Diagram 625-2755 (Rev. D) and 625-3100 (Rev. F)		Applies to models DFAA, DFAB, DFAC, DFBF, DFCB, DFCC, DFEB, DFEC, DFFB, DFGA, DFGB, DFJA, DFJB, DFJC, DFJD, DFLB, DFLC, DFLD, DFMB (625-2755) and models DFAA-DFMB plus DFCE, DFED, DQAA, DQAB, DQBA, DQBB (625-3100).
A (U)	CT21	U load leads (A phase)	CT dot must face the generator; CT terminal 1 connects to metering circuit, terminal 2/3 to ground.
B (V)	CT22	V load leads (B phase)	CT dot must face the generator; terminal 1 to metering circuit, terminal 2/3 to ground.
C (W)	CT23	W load leads (C phase)	CT dot must face the generator; terminal 1 to metering circuit, terminal 2/3 to ground.

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 QSX15 family

Part #	Description	Category
AF25544	Recommended air cleaner element - (heavy duty) primary element	air_filter
AF25545	Recommended air cleaner element - (heavy duty) secondary element	air_filter
0908-0101	Lead Acid Battery	battery
3375044	Torque Wrench	belt
19802521	ECM Dataplate	ecm
3331096	Cummins, Part No. 3331096	fuel_filter
3376807	Engine coolant and fuel filter wrench	fuel_filter
FS1007	Fleetguard® Nelson®, Part No. FS1007	fuel_filter
M-4376220	Juego Junta Superior N. ° de Pieza	gasket
M-4376221	Juego Junta Inferior N. ° de Pieza	gasket
3375049	Oil Filter Wrench	oil_filter
3406810	Combination Full-Flow/Bypass Lubricating Oil Filter Cummins Part No. 3406810	oil_filter
0908-0203		operator_manual
0908-0204		operator_manual
0908-0230	Generator Set Operator Manual	operator_manual
0908-0107	Radiator Information	other_service
0908-0110	Health and Safety (Diesel Generator Sets)	other_service
0908-0219	Alarm Module (option)	other_service
17200015	Engine Shutdown	other_service
17690172	Engine Braking System	other_service
17800006	Engine Model	other_service
3163156	Service cable for InPower™	other_service
3666423		other_service
3822735	Plastic bead blasting media	other_service
3886301	InPower™ electronic service tool	other_service
960-0174B		other_service
A035H139	Switch, Pushbutton	other_service
A040U808	Harness, Control − Door (Includes Items 30 & 31)	other_service
A046Y204	Shield, Wiring	other_service
M-3685996	Intake Valve	other_service
M-5473065	150mm Kit de Motor M-5473066	other_service
M-5473069	152mm Kit de Motor M-5473070	other_service
M-5473074	Kit de Motor M-5473075	other_service
TB3-5	Generator Set Control Panel Terminal Block	other_service
TB3-6	Generator Set Control Panel Terminal Block	other_service
ol204vt	Torque Peak	other_service
M-5473087	Piston Kit	piston_kit
M-5484414	Piston Pin	piston_pin
M-3686661	Valvula de escape - M-3686661	valve

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 QSX15-G8?

The Cummins/Onan QSX15-G8 engine has an oil capacity of 83.3 liters.

Which generators use the Cummins/Onan QSX15-G8 engine?

The Cummins/Onan QSX15-G8 powers 2 generator set(s), including Cummins/Onan 352DFEH, Cummins/Onan DFE.

What is a common problem with the Cummins/Onan QSX15-G8 engine?

A commonly reported issue on generators using the Cummins/Onan QSX15-G8 is: Over Current.