Cummins/Onan DFGC — Specs, Engine, Parts & Maintenance

Service parts for the DFGC

Grouped by system, with how many of each the parts manual calls for.

Cooling system

1 required

Prices captured from merchant listings; some links are affiliate links. Confirm against your serial number before ordering.

Specifications

Fuel	diesel
Oil capacity	84.0 L
Voltage options	120/240 V, 110/220 V, 118/230 V, 120/208 V, 127/220 V, 110/180 V, 118/200 V, 220/380 V, 240/416 V, 254/440 V, 277/480 V, 230/400 V, 347/600 V
Phase	3
Battery cranking	975 CCA
Battery voltage	12 V
Battery quantity	4
Starting system	24 V DC
Coolant capacity	167.0 L

Engine

Cummins/Onan VTA28-G3

Oil capacity	84.0 L
Coolant capacity	167.0 L
Displacement	28.0 L
Aspiration	turbocharged

Filters for the Cummins/Onan VTA28-G3

Engine-mounted filters the filter manufacturers list for this engine family. These come from the engine, not from this generator set’s own parts list, so confirm against your serial number before ordering.

System	Filter	Description	Cross-references
Oil filter	P550777	Lube Filter, Spin-On Bypass	CUMMINS 3021658, CUMMINS 33004232, NAPA 1749, BALDWIN B7577	FridayParts $43.56
Oil filter	P551670	Lube Filter, Spin-On Full Flow	CUMMINS 298670, CUMMINS 299670, NAPA 1970, CARBOCOL 0026	FridayParts $26.68

Listed for this engine in only one kind of machine, so they may depend on how the engine was installed:

System	Filter	Description	Cross-references
Fuel filter	P557440	Fuel Filter, Spin-On Secondary	CUMMINS BM78672, BALDWIN BF970, LPM 00013505994, WALGAHN-MOTORENTECHN 00811464	FridayParts $189.69
Fuel / water separator	P558000	Fuel Filter, Water Separator Spin-On Twist&Drain	CUMMINS 3308638, CUMMINS 3308683, NAPA 3405, NAPA 3693	KuduParts $24.00 FridayParts $25.66

Maintenance & consumables

for the Cummins/Onan VTA28-G3

Item	Spec	Part #
Air filter		—
Fuel filter		—
Oil filter		—
Battery		—
Belt		—
Coolant		—
Coolant filter	COOLANT FILTERS	CS-1075-1	Amazon eBay
Oil		—
Spark plug		—

Service intervals

Item	Action	Hours	Months	Notes
crankcase oil	Change	50 hr		First service — Drain and replace the crankcase oil after the first 50 hours of operation on new generator sets (break-in)
Rupture basin leak detect switch	Test		12 mo	Check once a year; in some areas weekly inspections may be required by safety code regulations

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	Angular alignment maximum T.I.R.	0.001	inch per inch of radius (center of shaft to indicator axis)	measuring deflection to bolt heads
Clearance	Clearance between exhaust pipes and combustible materials	12	inches (305 mm)	minimum
Clearance	Exhaust thimble diameter	12	inches (305 mm)	larger than diameter of exhaust pipe
Clearance	Float switch assembly float lift clearance below C-clip stop	1/8	inch (3 mm)	use a feeler gauge
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	Mounting base above floor	6	inches (152 mm)	minimum for maintenance access
Gap	MPU sensor to flywheel ring gear tooth	back it out one quarter turn	turn	sensor threaded in until it just touches gear tooth
Other	AVR Droop setting	5	% at full load, 0 PF
Other	AVR voltage regulation (load regulation)	approximately ±0.5	% RMS
Other	Angular alignment maximum T.I.R.	.001 inches per inch of radius	in/in	center of shaft to indicator axis
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, fully charged	approximately 1.260	specific gravity	at 80 F (27 C)
Other	Fuel lift height limit	6	feet	(1.8 meters) between fuel lift pump and bottom of dip tube
Other	GOV GAIN default value for paralleling applications	70	%
Other	Generator frequency	50 or 60	Hz	as nameplate rating
Other	Maximum cranking voltage drop	2	volts	difference between battery and starter terminals while cranking
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	Start delay adjustment range	0 to 300	seconds
Other	Stop delay adjustment range	0 to 600	seconds
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
Other	Under-frequency roll-off threshold (UFRO)	typically 59 Hz for 60 Hz applications and 49 Hz for 50 Hz applications	Hz	AVR UFRO pot preset
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	K19 engine idle oil pressure	20	psi (138 kPa)	idle
Pressure	K19 engine normal oil pressure	50-70	psi (345-482 kPa)	normal run
Pressure	K19 oil pressure shutdown/warning limits	shutdown 35 psi (241 kPa) run; warning 40 psi (276 kPa) run; shutdown 10 psi (69 kPa) idle; warning 15 psi (103 kPa) idle	psi (kPa)
Pressure	K38 engine idle oil pressure	20	psi (138 kPa)	idle
Pressure	K38 engine normal oil pressure	45-65	psi (310-448 kPa)	normal run
Pressure	K38 oil pressure shutdown/warning limits	shutdown 35 psi (241 kPa) run; warning 40 psi (276 kPa) run; shutdown 10 psi (69 kPa) idle; warning 15 psi (103 kPa) idle	psi (kPa)
Pressure	K50 engine idle oil pressure	20	psi (138 kPa)	idle
Pressure	K50 engine normal oil pressure	50-70	psi (345-482 kPa)	normal run
Pressure	K50 oil pressure shutdown/warning limits	shutdown 35 psi (241 kPa) run; warning 40 psi (276 kPa) run; shutdown 10 psi (69 kPa) idle; warning 15 psi (103 kPa) idle	psi (kPa)
Pressure	L10/M11 engine idle oil pressure	15	psi (103 kPa)	idle
Pressure	L10/M11 engine normal oil pressure	30-50	psi (207-345 kPa)	normal run
Pressure	L10/M11 oil pressure shutdown limit	20	psi (138 kPa)	run mode value
Pressure	L10/M11 oil pressure shutdown limit	8	psi (55 kPa)	idle mode value
Pressure	L10/M11 oil pressure warning limit	12	psi (83 kPa)	idle mode value
Pressure	L10/M11 oil pressure warning limit	25	psi (172 kPa)	run mode value
Pressure	Low oil pressure service limit while cranking	10	psi	service lubricating system if below
Pressure	Low oil pressure shutdown	below 14	psi (97 kPa)	time delayed ~10 seconds following starter disconnect
Pressure	Low oil pressure shutdown threshold	14	psi	less than this value shuts down
Pressure	Lubrication priming pressure	30	psi (207 kPa)	during system priming
Pressure	Maximum allowable exhaust back pressure	41	in H2O (10.2 kPa)	maximum
Pressure	NTA 855 engine normal oil pressure	35-50	psi (241-345 kPa)	normal run

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	soft water / E.G. / DCA mixture				Cooling system to be filled with soft water/E.G./DCA mixture (on-site review checklist).
Fuel	ASTM No. 2 Diesel				Check the engine manual for fuel specifications to determine acceptability. Never use galvanized or copper fuel lines, fittings or fuel tanks with diesel fuel systems.
Fuel	Diesel				Day tank fuel transfer pump maintains reservoir of diesel fuel in the day tank.
Grease	Lithium based grease	Mobilux No. 2 or Shell Alvania R3		2.74 oz (81 ml)	Generator end bearing. Temperature range -22F to +248F (-30C to +120C). Grease should be equally divided between the bearing, bearing cap cavity, and bearing cartridge cavity.
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.

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
1	FAULT 2 - INPUT NON-TIMED	Engine monitor TB2 terminal assignment
10	PRE-HIGH ENGINE TEMPERATURE	Engine monitor TB2 terminal assignment
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	Indicates local or remote Emergency Stop.	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. Can be reset only at the PCC front panel.
11	PRE-LOW OIL PRESSURE	Engine monitor TB2 terminal assignment
12	SWITCH OFF	Engine monitor TB2 terminal assignment
13	LOW ENGINE TEMPERATURE	Engine monitor TB2 terminal assignment
14	LOW FUEL - INPUT	Engine monitor TB2 terminal assignment
15	LOW FUEL - OUTPUT	Engine monitor TB2 terminal assignment
16	SHUT-DOWN	Engine monitor TB2 terminal assignment
2	FAULT 2 - OUTPUT SHUTDOWN	Engine monitor TB2 terminal assignment
200	LOW OIL PRESSURE	Indicates engine oil pressure has dropped to an unacceptable level.	Warning	If generator is powering critical loads and cannot be shut down, wait until next shutdown period and then follow 201-SHUTDOWN procedure. Access the Oil Pressure menu prior to clearing the fault.
201	LOW OIL PRESSURE	Indicates engine oil pressure has dropped below the shutdown trip point.	Shutdown	Check oil level, lines and filters; replenish if low; reset control and restart.
204	OIL PRES SENDER	Indicates that the control has sensed that the engine oil pressure sender is out of its working range.	Warning	Check that the engine oil pressure sender is properly connected.
210	LOW COOLANT TEMP	Warning occurs when engine coolant temperature is 70°F (21°C) or lower.	Warning	Indicates engine coolant heater is not operating or is not circulating coolant. Check coolant heater power supply, low coolant level, and heater element current draw.
211	HIGH COOLANT TEMP	Indicates the engine coolant temperature is getting close to the recommended maximum temperature limit: 215° F (102° C) − standby or 207° F (97° C) − primary.	Warning	Reduce load if possible; check air inlets and outlets and remove obstructions to airflow.
212	HIGH COOLANT TEMP	Indicates engine has overheated (coolant temperature has risen above the shutdown trip point: 215 F (102 C) - standby or 207 F (97 C) - primary).	Shutdown	Check for obstructions to cooling airflow; check fan belt; check coolant mixture; check blower fan and circulation pumps; reset control and restart.
213	COOLANT SENDER	Resistance of the coolant temperature sender is out of range.	Warning	Check the resistance of the sender; should be 500 to 2k ohms.
214	LOW COOLANT LVL	Indicates engine coolant level has fallen below the trip point.	Warning	Check coolant level in radiator and coolant recovery bottle; replenish if low; look for leaks.
215	LOW COOLANT LVL	Indicates engine coolant level has fallen below the trip point.	Shutdown	Allow engine to cool; check coolant level and leakage points; reset control and restart.
220	MAG PICKUP	Mag pickup speed indication is not being sensed or does not match generator set output frequency.	Shutdown	Restart and check RPM; check PCC model setting; inspect and test MPU.
221	FAIL TO CRANK	Possible fault with control or starting system.	Shutdown	Check fuse F3 on the Engine Interface board; check battery cable connections; recharge or replace the battery.
222	OVERCRANK	Possible fuel system problem.	Shutdown	Check for empty fuel tank, leaks, plugged fuel lines; replace dirty fuel or air filter; reset and restart.
223	OVERSPEED	Indicates engine has exceeded normal operating speed. (115% ±1% of nominal).	Shutdown	Check mechanical fuel linkage and governor module/digital board duty cycle.
224	FAIL TO SYNCHRONIZE	Generator set has not synchronized to the system bus within the allowable time frame.	Warning	Check governor system stability; adjust governing and synchronizer parameters; check fuel system.
226	FAIL TO CLOSE	Paralleling breaker has been given a signal to close, but has not closed properly.	Shutdown	Verify breaker charging mechanism; check close signal; verify auxiliary contact signals.
230	LOW DC VOLTAGE	Indicates battery voltage is below 10 VDC.	Warning	Recharge or replace the battery; check the battery charger fuse. Clean and tighten battery cable connections. Check engine DC alternator; replace if normal charging voltage is not obtained. Check float level if applicable.
231	HIGH DC VOLTAGE	Indicates battery voltage exceeds 32 VDC.	Warning	Lower battery charger float level if applicable; check engine DC alternator.
232	WEAK BATTERY	Indicates battery voltage drops below 60% of nominal for two seconds, during starting.	Warning	See LOW DC VOLTAGE 230.
240	LOW FUEL−DAY	Indicates day tank fuel supply is running low.	Warning	Check fuel supply and replenish as required.
241	LOW FUEL	Low fuel signal received.	Warning	Check fuel supply and replenish; check for short to ground in external wiring.
250	EEPROM ERROR	PCC memory error; data corruption of critical operating parameters.	Shutdown	Perform the initial start setup procedure; if the set shuts down on the same EEPROM ERROR message, replace the digital board (A32).
251	EEPROM ERROR	PCC memory error; data corruption of noncritical operating parameters.	Warning	Perform the adjustment procedures; if the same message occurs, perform calibration procedures; if the message persists, replace the digital board (A32).
252	EEPROM ERROR	PCC memory error; data corruption of noncritical operating parameters.	Warning	Verify values/choices selected and repeat the save operation; if the same message occurs, replace the digital board (A32).
260	CUSTOMER FAULT 1	When this customer defined input is closed to ground, the corresponding fault message is displayed. Programmable to initiate a shutdown or a warning.	Warning	Isolate source of false signal; repair external wiring or replace A34.
261	GROUND FAULT	When a customer defined input is closed to ground, the corresponding fault message is displayed. Default message; editable for customer site requirements.	Warning	Isolate source of false signal; repair external wiring or replace A34.
262	RUPTURE BASIN	When a customer defined input is closed to ground, the corresponding fault message is displayed. Default message; editable for customer site requirements.	Warning	Isolate source of false signal; repair external wiring or replace A34.
263	HIGH GEN TEMP	When a customer defined input is closed to ground, the corresponding fault message is displayed. Default message; editable for customer site requirements.	Warning	Isolate source of false signal; repair external wiring or replace A34.
270	PHASE ROTATION	The phase relationship between the generator set and the system bus is not matched.	Shutdown	Verify genset phase rotation matches bus; verify control wiring to bus PT module.
272	FIRST START	PowerCommand control is not receiving a proper signal from the system master first start sensor.	Warning	Verify Master First Start Sensor and interconnection wiring.
3	FAULT 1 - INPUT TIMED	Engine monitor TB2 terminal assignment
301	HIGH AC VOLTAGE	One or more phase voltages exceeded 130% of nominal, or exceeded 110% of nominal for 10 seconds.	Shutdown	Set display to GEN, VOLTS, L-N; determine if the output voltage the control sees is low or high; isolate PCC/alternator/excitation circuit.
303	LOW AC VOLTAGE	One or more phase voltages dropped below 85% of nominal for 10 seconds.	Shutdown	Check PMG/field wiring, rotating rectifier, load and connectors.
313	UNDER FREQUENCY	Indicates that engine speed has dropped below 90% of nominal for 10 seconds. Five seconds before shutdown, a Load Dump signal is initiated.	Shutdown	Check fuel supply, intake air supply and load.
320	OVERCURRENT	Indicates that generator output current has exceeded 110% of rated for 60 seconds.	Warning	Check load and load lead connections.
321	OVERCURRENT	Indicates that generator output current has exceeded 110% of rated, and that a PCC time/current calculation has initiated an overcurrent shutdown.	Shutdown	Check load and load lead connections.
322	SHORT CIRCUIT	Indicates that generator output current has exceeded 175% of rated.	Shutdown	Check load and load lead connections.
330	OVERLOAD	Three-phase power output exceeds 105% of standby (or 115% of prime) rating.	Warning	Check load and load lead connections.
335	REVERSE POWER	Power is flowing into the generator set rather than out from the unit.	Shutdown	Verify CT connections, load sharing lines, and generator set frequency/voltage.
337	LOSS OF EXCITATION	Alternator excitation system is improperly adjusted or has failed.	Shutdown	Check output voltage calibration, load sharing lines, and leading power factor loads.
4	FAULT 1 - OUTPUT SHUTDOWN	Engine monitor TB2 terminal assignment
5	LAMP TEST/RESET	Engine monitor TB2 terminal assignment
6	OVERCRANK	Engine monitor TB2 terminal assignment
7	OVERSPEED	Engine monitor TB2 terminal assignment
8	HIGH ENGINE TEMPERATURE	Engine monitor TB2 terminal assignment
9	LOW OIL PRESSURE	Engine monitor TB2 terminal assignment
FAULT 1	Fault 1 (Red)	Undedicated customer-defined fault; may be programmed as timed or non-timed shutdown or fault light only.	Shutdown	Service as required by the customer-supplied fault indicating switches.
FAULT 2	Fault 2 (Red)	Undedicated customer-defined fault, same features as Fault 1.	Shutdown	Service as required by the customer-supplied fault indicating switches.
GF	Ground Fault Alarm (Optional)	Ground fault relay monitors neutral to ground connection and line to neutral, activating a fault alarm when the connection is broken or a ground fault is sensed.	Warning	Clear fault condition by pushing the Run/Stop (Reset)/Remote switch to Reset (auto reset link set at factory).
HET	High Engine Temperature (Red)	Engine shut down because of excessively high engine coolant temperature (greater than 230 deg F).	Shutdown	Check coolant level and leaks; service cooling system; reset engine control.
HI ENG TEMP	High Engine Temperature	Engine shut down due to critically high coolant temperature (above 215F/102C).	Shutdown
LET	Low Engine Temperature (Yellow)	Engine temperature is less than 70 deg F and the engine might not start.	Warning	Plug in, repair or install engine coolant and oil heaters.
LO FUEL	Low Fuel	Fuel supply is marginally low, if equipped (Detector-12).	Warning
LO OIL PRES	Low Oil Pressure	Engine shut down due to critically low oil pressure (below 14 psi/97 kPa).	Shutdown
LOP	Low Oil Pressure (Red)	Engine shut down because of excessively low engine oil pressure (less than 14 psi).	Shutdown	Check oil level and oil leaks; service lubricating system; reset engine control.
LOW ENG TEMP	Low Engine Temperature	Engine water jacket temperature is 70F/21C or lower; indicates possible inoperative coolant heater (Detector-12).	Warning
LOW FUEL	Low Fuel (Yellow)	Fuel level in the supply tank has dropped below the reserve necessary to run the set at full load for the prescribed number of hours.	Warning	Fill the main fuel supply tank with the appropriate grade of fuel.
OC	Overcrank (Red)	Engine shut down because it did not start during the timed cranking period (approximately 75 seconds, including two rest periods).	Shutdown	Service the set as necessary; reset engine control.
OS	Overspeed (Red)	Engine shut down because of overspeed.	Shutdown	Adjust the Electronic Overspeed Module; check governor for binding; reset engine control.
OVERCRANK	Overcrank	Starter locked out because of excessive cranking time (limited to 75 seconds).	Shutdown
OVERSPEED	Overspeed	Engine shut down because of excessive speed.	Shutdown
PRE HI ENG TEMP	Pre-High Engine Temperature	Coolant temperature is marginally high (205F/97C or higher).	Warning	Attend to when generator set is shut down.
PRE LO OIL PRES	Pre-Low Oil Pressure	Engine oil pressure is marginally low (20 psi/138 kPa or less).	Warning	Attend to when generator set is shut down.
PRE-HET	Pre High Engine Temperature (Yellow)	Engine coolant temperature is abnormally high (greater than 220 deg F).	Warning	Shut down if possible or disconnect non-critical loads; service cooling system.
PRE-LOP	Pre Low Oil Pressure (Yellow)	Engine oil pressure is abnormally low (less than 20 psi).	Warning	Shut down if possible or disconnect non-critical loads; service lubricating system.
RUN	Run (Green)	Green lamp comes on when both primary and secondary starter circuits open after unit starts.	Info
SWITCH OFF	Switch-off (Flashing Red)	The Run/Stop/Remote switch is in the Stop position, preventing remote automatic operation.	Info	Push the Run-Stop-Remote switch to Remote.

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 adjustment

⚠ Accidental starting of the generator set during this procedure presents the hazard of severe personal injury or death. Make sure to disconnect the negative (-) battery cable(s) before beginning.

Tools: Dial indicator, Wooden shims

Disconnect the negative (-) battery cable(s) before beginning.
Fasten a dial indicator to the generator shaft or cooling fan with sensing point on capscrew head or flat surface of drive disc at 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.
Record maximum positive and negative dial indicator readings as the engine completes one revolution.
T.I.R. equals the sum of the maximum positive and negative readings.
Maximum T.I.R. should not be more than .001 inch for each inch of radius.
Remove equal shims from under both generator mounting feet to lower the generator.

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 (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.

Governor Calibration Checks adjustment

Tools: Frequency meter or tachometer, Jumper wire

Start the generator set.
Adjust engine no-load speed to the desired allowable speed droop using the Run Speed potentiometer.
With no load, turn GAIN clockwise slowly until engine speed oscillates.
Reduce GAIN slowly counterclockwise until engine speed is stable.
Upset the governor by momentarily shorting terminals 7 and 10 on the governor control.
Apply and remove loads to check generator set response.

HC4-7 Axial Alignment Procedure adjustment

Tools: Dial indicator with magnetic base or clamp

Check only when an objectionable vibration is present.
Fasten dial indicator holding device to skid base, engine block, or generator shell with magnetic base or clamp.
Position sensor point on the generator shaft hub.
Bar the engine over in a clockwise rotation as viewed from engine flywheel through a couple of rotations.
Record indicator readings in eight equally spaced points around the shaft diameter.
Remove the capscrews connecting drive discs and flywheel and mark discs and flywheel.
Rotate engine or generator so drive disc holes are repositioned 180 degrees from original location.
Put capscrews back in and retorque. Recheck shaft alignment.
If runout unchanged, rotate discs to 30, 60 or 90 degrees from original location.
If T.I.R. does not improve, inspect flywheel pilot and drive disc runouts.

P7 Axial Alignment Procedure adjustment

Check only when an objectionable vibration is present.
Remove the capscrews connecting drive discs and flywheel.
Mark the drive discs and flywheel with respect to each other.
Rotate engine or generator so drive discs holes are repositioned two bolt holes from original location.
Put capscrews back in and retorque. Recheck/record vibration levels.
Repeat this test until drive disc holes are repositioned 180 degrees from original location.
Review vibration data and position drive disc in lowest recorded level location.

UFRO Adjustments adjustment

⚠ Use an insulated handle screw driver to prevent electrical shock.

Tools: Insulated handle screwdriver, Frequency meter or tachometer

Make a note of the no-load frequency.
Determine roll-off frequency by turning the governor speed pot until the LED lights; if okay go to step 5.
Adjust the governor speed pot to the proper roll-off frequency.
Turn the UFRO pot until LED goes off, then slowly turn it back until the LED just goes on.
Adjust the governor speed pot back to the initial frequency setting.

Voltage and Voltage Stability Adjustments adjustment

⚠ Touching uninsulated high voltage parts inside the control and power output boxes can result in severe personal injury or death.

Tools: Insulated handle screwdriver, AC voltmeter

Use the control panel mounted voltage trimmer, if provided, for small voltage adjustments.
Measure generator output voltage while running without load at nominal frequency.
If trimmer is insufficient, lock it at midpoint.
Turn the VOLTS pot fully counterclockwise and the STABILITY pot to its midpoint.
If the red LED lights, refer to Jumper Reconnections and UFRO Adjustments.
Turn the VOLTS pot clockwise until rated voltage is obtained.
If voltage becomes unstable with a large load, turn the STABILITY pot clockwise until stable.
Check and readjust the VOLTS pot each time the STABILITY pot is readjusted.

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.

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

Voltage	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.
110/180	3			Reconnection diagram (Figure 5-2); 50 Hz
110/220	1			Reconnection diagram (Figure 5-2); 50 Hz
118/200	3			Reconnection diagram (Figure 5-2); 50 Hz
118/230	3			Reconnection diagram (Figure 5-2); 50 Hz
120/208	3			Reconnection diagram (Figure 5-2); 60 Hz
120/240	1			Reconnection diagram (Figure 5-2); phase sequence U-V-W
127/220	3			Reconnection diagram (Figure 5-2); 60 Hz
220/380	3			Reconnection diagram (Figure 5-2); 60 Hz
230/400	3			Reconnection diagram (Figure 5-2); 50 Hz
240/416	3			Reconnection diagram (Figure 5-2); 60 Hz
254/440	3			Reconnection diagram (Figure 5-2); 60 Hz
277/480	3			Reconnection diagram (Figure 5-2); 60 Hz
347/600	3			Reconnection diagram (Figure 5-2); 60 Hz

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 engine is in the Cummins/Onan DFGC?

The Cummins/Onan DFGC is powered by the Cummins/Onan VTA28-G3 engine.

What fuel does the Cummins/Onan DFGC use?

The Cummins/Onan DFGC runs on diesel.

How much oil does the Cummins/Onan DFGC take?

The Cummins/Onan VTA28-G3 engine in the Cummins/Onan DFGC has an oil capacity of 84.0 liters.

How much coolant does the Cummins/Onan DFGC hold?

The Cummins/Onan DFGC cooling system holds 167 liters (44.1 US gallons) for the radiator system including the engine, per the manufacturer specification sheet.

What voltages is the Cummins/Onan DFGC available in?

The Cummins/Onan DFGC is offered in 120/240 V, 110/220 V, 118/230 V, 120/208 V, 127/220 V, 110/180 V, 3-phase.

How many cold cranking amps does the Cummins/Onan DFGC require?

The Cummins/Onan DFGC uses 4 batteryies, 12 V each, 975 CCA, per the manufacturer specification sheet. The starting system is 24 V DC.

Repair guides

Step-by-step procedures compiled from the Cummins/Onan service manual for this model.

Parts

Part #	Description	Qty	System
518-0548-24	Clamp, Hose	2	Hose	Amazon eBay
960-0504	PCC Control Service Manual	*	Service manual	Amazon eBay
960-0507	Detector Control Service Manual	**	Service manual	Amazon eBay $49.00
CS-1075-1	COOLANT FILTERS		Coolant filter	Amazon eBay
CS-1367-2	TYPICAL COOLANT HEATER		Coolant heater	Amazon eBay
EXS-1583-3	CONTROL HEATER		Control heater	Amazon eBay
332-2634	Clamp, Hose	1	Service part / kit	Amazon eBay
518-0548-42	Clamp, Retainer 4 Prior To December 1996 Production (Mounted On Top And Side Of Control Box Wrapper)	20	Service part / kit	Amazon eBay
EXS-1036-1	RAIN CAP		Service part / kit	Amazon eBay
M-1808-4	TYPICAL INSTALLATION		Service part / kit	Amazon eBay

Service, wear & replacement parts referenced for this model and its engine — confirm the exact part for your serial number. See the full parts catalog to search and cross-reference.

Available documents

Spec sheet — 0080258 (Cummins/Onan)Spec sheet — Cummins-installation-manual-DFAA-DFAB-DFAC-DFBC-DFBF-DFBD-DFBE-DFBF-DFCB-DFCC-DFCE-DFEB-DFEC-DFED-DFFA-DFFB-DFGA-DFGB-DFGC-DFJA-DFJB-DFJC-DFJD-DFLA-DFLB-DFLC-DFLD-DFLE-DFMB-DQAA-DQAB-DQBA-DQBB (Cummins/Onan)Parts manual — 0932-0112 Onan Post-Sale Literature Index (07-1998) (Cummins/Onan)Service manual — 960-0504 Onan DFxx series Generator Control Service Manual 04-1993 (Cummins/Onan)Service manual — 960-0507C Cummins DFAA thru DFMB DQAA Service Manual (2-2004) (Cummins/Onan)Service manual — 960-0611 Onan DFGA DFGB DFGC Installation Manual (8-1990) (Onan)Service manual — 960-0619D Cummins DFA DFB DFC DFE DFF DFG DFJ DFL DFM DQA DQB Installation (6-2003) (Cummins/Onan)Service manual — Cummins-3100-PowerCommand-DFAA-DFAB-DFAC-DFBC-DFBD-DFBE-DFBF-DFCB-DFCC-DFCE-DFEB-DFEC-DFED-DFFA-DFFB-DFGA-DFGB-DFGC-DFJA-DFJB-DFJC-DFJD-DFLA-DFLB-DFLC-DFLD-DFLE-DFMB-DQAA-DQAB-DQBB (Cummins/Onan)Service manual — DFxx Generator Set Service Manual PCC3100 (Cummins/Onan)Service manual — Detector Control Generator Set Service Manual (Cummins/Onan)

This page was generated from the 10 manufacturer documents above by automated extraction; every figure shown is copied from one of them. How the data is compiled.

Cummins/Onan DFGC Generator Set

Service parts for the DFGC

Cooling system

Specifications

Engine

Filters for the Cummins/Onan VTA28-G3

Maintenance & consumables

Service intervals

Service specifications

Recommended fluids

Fault codes

Procedures

Voltage reconnection

Common questions

Repair guides

Parts

Available documents