Home›Engines›Cummins/Onan 6CT8.3G

Cummins/Onan 6CT8.3G Engine

Name: Cummins/Onan 6CT8.3G Engine
Brand: Cummins/Onan

The Cummins/Onan 6CT8.3G is an engine. It powers generator sets from Cummins/Onan, including the DGEA. It holds 19 L (5.0 gal) of oil and 26 L (6.9 gal) of coolant.

Also known as: Cummins 6CT8.3G

19.0 L

Oil capacity

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

Engine specifications

Oil capacity	19.0 L
Coolant capacity	26.0 L

Generator sets powered by this engine

Cummins/Onan DGEA

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

Common problems

The FAULT 1 or FAULT 2 fault lamp lights. Engine shuts down immediately, engine runs for several seconds and then shuts down, or engine continues to run.
Fix: The standard undesignated fault functions are programmed to shut down the set when a fault is sensed. Fault 1 is time delayed while Fault 2 is immediate. The nature of the fault is an optional selection that is determined when the set installation is designed. The undesignated fault functions may also be programmed for non-shutdown or non-time delay.
SWITCH OFF lamp flashes.
Fix: Indicates Run/Stop/Remote switch is in the Stop position which will prevent automatic starting if an automatic transfer switch is used. Move the Run/Stop/Remote switch to the Remote position for automatic starting.
PRE LO OIL PRES lamp lights. Engine continues to operate.
Cause: Indicates engine has overheated (engine temperature has risen above 222°F/106°C) or coolant level is low (sets with coolant level sensor).
PRE HI ENGINE TEMP lamp lights. Engine continues to operate.
Cause: Indicates engine has begun to overheat and engine temperature has risen to approximately 215°F (102°C).
Fix: If generator is powering non-critical and critical loads and cannot be shut down, use the following: a. Reduce load if possible by turning off non-critical loads. b. Check air inlets and outlets and remove any obstructions to airflow.
OVERCRANK lamp lights and engine stops cranking.
Fix: A. Check for empty fuel tank, fuel leaks, or plugged fuel lines and correct as required. b. Check for dirty fuel filter and replace if necessary (see Maintenance section). c. Check for dirty or plugged air filter and replace if necessary (see Maintenance section). d. Reset the control and restart after correcting the problem. Contact an authorized service center for service if none of the above.
No AC output voltage.
Fix: Field breaker is tripped. Reset breaker. Contact an authorized service center if voltage buildup causes breaker to trip.
LO OIL PRES lamp lights. Engine shuts down.
Fix: Check oil level, lines and filters. If oil system is OK but oil level is low, replenish. Reset control and restart. Contact an authorized service center if oil pressure is not in the range of 25 to 40 psi (172 to 275 kPa).
LO FUEL LAMP lights. Engine shuts down and LO OIL PRES lamp lights.
Fix: Indicates engine has run out of fuel. Check fuel level and replenish as required.
LO FUEL lamp lights. Engine continues to run.
Fix: Indicates diesel fuel supply is running low. Check fuel supply and replenish as required.
LO ENG TEMP lamp lights. Set is in standby mode but is not operating.
Fix: A. Coolant heater not connected to power supply. Check for blown fuse or disconnected heater cord and correct as required. b. Check for low coolant level and replenish if required. Look for possible coolant leakage points and repair as required. c. Contact an authorized service center for service if none of the above.
Green RUN lamp does not light following engine startup.
Fix: Indicates possible Start/Disconnect relay failure. Contact an authorized service center for assistance.
Fault lamp lights but no fault exists. Engine gauges show oil pressure, engine temperature, and frequency (speed) are within normal limits.
Fix: The monitor board or a sensor may be at fault. Contact an authorized service center for service.
Engine will not crank.
Fix: A. Fault lamp on. Correct fault and reset control. b. Poor battery cable connections. Clean the battery cable terminals and tighten all connections. c. Discharged or defective battery. Recharge or replace the battery. d. Emergency stop button (if equipped) pushed in. To reset, pull switch out and move Run/Stop/Remote switch to Stop position. Then push test switch to Reset/Lamp position. e. Contact an authorized service center if none of the above.
Engine starts from generator control panel but will not start automatically or from a remote panel.
Fix: Remote circuit breaker is tripped. Reset breaker and restart. Contact an authorized service center if breaker trips after resetting.
Engine runs and then shuts down, OVERSPEED lamp lights.
Fix: Indicates engine has exceeded normal operating speed. Contact an authorized service center for service.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan 6CT8.3G.

Maintenance schedule

Item	Part #	Interval
Air filter	—	250 hr
Fuel filter	—	100 hr
Oil filter	LS1174s	250 hr	Amazon eBay
Battery	B-45	50 hr	Amazon eBay $39.64 KuduParts $135.00
Belt	—	300 hr
Coolant	—	100 hr
Oil	—	500 hr
Spark plug	—	1000 hr

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

Service intervals

Item	Action	Hours	Months	Notes
Check Coolant Level	Check	8 hr		Daily
Check Fuel Level	Check	8 hr		Daily
Check Oil Level	Check	8 hr		Daily
Coolant Heater	Check	8 hr		Verify hot coolant is being discharged from the outlet hose.
Coolant Level	Check	8 hr
Drain Water from Fuel Filter	Drain	8 hr		Daily; drain 1 cup or more of fuel to remove water and sediment.
Exhaust Condensate Trap	Drain	8 hr
Fuel Filter(s)	Drain	8 hr		Drain 1 cup or more of fuel to remove water and sediment. Refer to engine operation and maintenance manual for procedure.
Fuel Level	Check	8 hr
Fuel Tanks (water and sediment)	Drain	8 hr		Drain 1 cup or more of fuel to remove water and sediment.
Inspect Genset	Check	8 hr		Check for oil, fuel, cooling and exhaust system leaks. Check exhaust system audibly and visually with set running and repair any leaks immediately.
Inspect Set	Inspect	8 hr		Daily; check for oil, fuel, cooling, and exhaust system leaks.
Oil Level	Check	8 hr		Keep oil level near the dipstick high mark without overfilling.
Air Cleaner	Clean	50 hr		Clean if required. Perform more often in dusty conditions.
Battery Charging System	Check	50 hr
Charge Air Piping	Check	50 hr
Check Anti-freeze and DCA Concentration	Check	50 hr		Weekly
Check Battery Charging System	Check	50 hr		Weekly
Check Battery Level and Specific Gravity	Check	50 hr		Weekly
Check Coolant Heater	Check	50 hr		Weekly
Check Drive Belt Tension	Check	50 hr		Weekly; visually check belts for evidence of slippage.
Check Generator Air Outlet	Check	50 hr		Weekly
Crankcase Oil	Drain	50 hr		First service — Break-in: drain and replace the crankcase oil after the first 50 hours of operation on new generator sets.
Crankcase oil	Change	50 hr		First service — Drain and replace after first 50 hours of operation on new generator sets.
Drain Exhaust Condensate Trap	Drain	50 hr		Weekly
Drain Water and Sediment from Fuel Tanks	Drain	50 hr		Weekly; drain 1 cup or more.
Starting Batteries	Check	50 hr
Check Air Cleaner (clean if required)	Check	100 hr		Monthly; clean if required; perform more often in extremely dusty conditions.
Clean Generator Assembly	Clean	100 hr		Monthly
Anti-freeze and DCA Concentration	Check	250 hr	3 mo	Refer to engine operation and maintenance manual.
Crankcase Oil and Filter	Change	250 hr	3 mo	If genset is used for prime power applications, change oil and filter every 3 months or 250 hours. If used for standby applications, change oil every 12 months or 250 hours, whichever comes first.
Drive Belt Tension	Check	250 hr	3 mo	Visually check belt for evidence of wear or slippage. Replace if hard or brittle. Refer to engine operation and maintenance manual.
Fuel Filters	Change	250 hr	3 mo	Refer to engine operation and maintenance manual.
Governor Adjustment	Check	250 hr	3 mo
Radiator Hoses for Wear & Cracks	Check	250 hr	3 mo
Air Cleaner Element	Change	500 hr		Perform more often in dusty conditions. Replace yearly or sooner if service indicator button pops up.
Change Air Cleaner Element	Change	500 hr	6 mo	Perform more often in extremely dusty conditions.
Change Crankcase Oil and Filter	Change	500 hr	6 mo	Perform more often in extremely dusty conditions.
Change Fuel Filters	Change	500 hr	6 mo
Check Governor Adjustment	Check	500 hr	6 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
Clearance	Float switch lift below C-clip stop	1/8	inch (3 mm)
Clearance	Overspeed switch magnet-to-fly arm air gap (minimum)	0.005	inches (0.13 mm)
Gap	Mechanical overspeed switch air gap between magnet and fly arm (replace switch if less)	0.005	inches (0.13 mm)
Other	AVR DROOP preset at factory	five percent droop at full load and zero power factor
Other	Battery electrolyte corrected specific gravity (fully charged)	1.260		electrolyte temperature corrected
Other	Battery recharge threshold specific gravity	1.215
Other	Battery specific gravity	1.260		at 77°F (25°C)
Other	Battery specific gravity temperature correction	four gravity points (0.004) for every ten degrees above 80 F (27 C)
Other	Battery specific gravity, fully charged	approximately 1.260	at 80°F (27°C)
Other	Coolant level	50	mm	below radiator cap opening
Other	Cycle crank crank and rest time	7 to 20	seconds
Other	Cycle crank number of cycles	3, 4, or 5
Other	Cycle cranking (12-lamp control)	3 cycles of 15 seconds
Other	ECM fuse F1 (starter solenoid circuit)	20	amps
Other	ECM fuse F2 (fuel solenoid circuit)	20	amps
Other	ECM fuse F3 (continuous B+ to remote circuits)	15	amps
Other	ECM fuse F4 (ECM circuits)	5	amps
Other	ECM fuse F5 (engine gauge circuits)	5	amps
Other	Frequency adjustment range	±5%	%	genset running
Other	Fuse A31-F1 (control B+)	5	Amp	Engine Interface board
Other	Fuse A31-F3 (auxiliary B+)	5	Amp	Engine Interface board; panel lights, run and start relays
Other	Fuse A38-F1 (Network B+)	10	Amp	Governor Output Module
Other	Fuse A38-F2 (Switched B+)	10	Amp	Governor Output Module
Other	Fuse A38-F3 (Governor B+)	10	Amp	Governor Output Module
Other	Fuse TB-Bat F1 (Customer B+)	20	Amp	Engine Harness Assembly
Other	GOV RAMP adjustment range	0 through 10	seconds
Other	Governor droop adjustment range	within 5	percent of nominal frequency (3 Hz for 60Hz sets, 2.5 Hz for 50Hz sets)
Other	Low oil pressure / high engine temperature fault time delay	about 10	seconds	following starter disconnect and inhibited during cranking
Other	Overcrank limit (Sentinel)	60	seconds
Other	Overcrank option limit (Detector)	75	seconds
Other	Overcrank time limit	75	seconds
Other	Overspeed warning range 60 Hz sets	2000 to 2200	RPM
Other	REG VHZ adjustment range	1 through 50 (normal range 7 through 21)
Other	Random voltage variation	±1	%	for constant loads
Other	Response jumper setting - 90 to 550 kW	B to C
Other	Response jumper setting - over 550 kW	A to B
Other	Response jumper setting - under 90 kW	A to C
Other	Setup/calibration menu access code	574
Other	Standard cycle cranking (Detector)	three 15-second cranking cycles with two 15-second rest periods
Other	Start delay adjustment range	0 to 300	seconds	remote starting in Auto mode
Other	Starter disconnect speed	450 to 570	RPM
Other	Stop delay adjustment range	0 to 600	seconds	remote stopping in Auto mode
Other	Trailer brake shoe adjustment back-off	10	clicks
Other	Trailer surge brake actuator stroke length (service brakes if exceeds)	1	inch (25 mm)
Other	Under-frequency roll-off (UFRO) threshold, 50 Hz applications	49	Hz
Other	Under-frequency roll-off (UFRO) threshold, 60 Hz applications	59	Hz
Other	Voltage adjustment range	±5%	%	genset running
Other	Voltage regulation	±2	%	from no load to full load
Pressure	Engine oil pressure (normal)	30 to 65	psi (207 to 449 kPa)	at normal operating temperature
Pressure	Engine oil pressure range (low oil pressure troubleshooting)	25 to 65	psi (172 to 449 kPa)
Pressure	Fuel shutoff valve rating (TB1-8 and TB1-5)	not more than 0.5	amps	120 or 240 VAC
Pressure	Idle oil pressure	10 - 30	psi (69 - 207 kPa)	idle
Pressure	Idle oil pressure	10-30	psi (69-207 kPa)	idle
Pressure	Idle oil pressure (normal)	10-30	psi (69-207 kPa)	Engine model 6C, idle
Pressure	Idle oil pressure shutdown limit	8	psi (55 kPa)	idle
Pressure	Idle oil pressure warning limit	12	psi (83 kPa)	idle
Pressure	Low Oil Pressure shutdown threshold	14	psi (97 kPa)
Pressure	Low Oil Pressure shutdown threshold (less than)	14	psi
Pressure	Low oil pressure cutout switch test threshold (service lubricating system if less)	10	psi	while cranking
Pressure	Low oil pressure shutdown	14	psi

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	Notes
Coolant		soft water/E.G./DCA mixture		Installation review checklist item: cooling system must be filled with soft water/E.G./DCA mixture.
Coolant	50/50 mix of water and antifreeze	Balanced coolant mixture of water, antifreeze and coolant additives		Drain and replace the mixture every 6 months or after 500 hours of operation. Do not add cold coolant to a hot engine; allow engine to cool below 120 F (50 C) before adding coolant.
Engine oil		Refer to the Cummins engine Operation and Maintenance Manual for lubricating oil classification/recommendations/specifications		Gensets are shipped with oil added.
Engine oil	SAE 5W synthetic	API CC/CD; sulphated ash max 1.85%; pour point 9°F (5°C) below lowest expected temperature; viscosity max 10,000 mPa·s at -31°F (-35°C) and min 4.1 mm²/s at 212°F (100°C)	below -23°C	For ambient consistently below -10°F (-23°C) and no engine warm-up provision
Engine oil	10W-30	API CC/CD	-23°C to -10°C	For ambient -10°F (-23°C) to 14°F (-10°C)
Engine oil	15W-40	API CC/CD	above -10°C	For ambient 14°F (-10°C) and above
Engine oil	20W-40	API CC/CD	above 0°C	For ambient 32°F (0°C) and above
Fuel	No. 2 diesel			Engine primarily designed for No. 2 diesel; No. 1 fuel or similar acceptable if meets specifications
Fuel	diesel			Do not use zinc coated or copper fuel lines with diesel fuel.
Hydraulic oil	DOT-3			Trailer master cylinder reservoir - keep at least half full

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; generator build-up is inhibited and engine governed at 800 RPM.	Warning	Remove ground from the engine idle input to return to normal speed and voltage.
102	EMERGENCY STOP	Indicates local or remote Emergency Stop.	Shutdown	Pull the button out; move the Run/Off/Auto switch to Off; press the Reset switch; select Run or Auto as required. Can only be reset at the PCC front panel.
200	LOW OIL PRESSURE	Indicates engine oil pressure has dropped to an unacceptable level.	Warning	If powering critical loads, wait until next shutdown period and follow 201-SHUTDOWN procedure; check oil pressure via menu prior to clearing 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. Oil pressure limits in Table 4-3.
204	OIL PRESS SENDER	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, indicating the engine coolant heater is not operating or is not circulating coolant.	Warning	Indicates engine coolant heater is not operating or is not circulating coolant; check coolant heater power supply/fuse, low coolant level, and open heater element.
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) prime.	Warning	Reduce load if possible; check air inlets/outlets; follow 212-SHUTDOWN procedure if engine can be stopped.
212	HIGH COOLANT TEMP	Indicates engine has overheated (coolant temperature above the shutdown trip point: 223°F (106°C) standby or 215°F (102°C) prime).	Shutdown	Allow engine to cool; check for obstructions to cooling airflow, check fan belt, check coolant mixture, check blower fan and circulation pumps; reset control and restart after correcting problem.
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; look for leakage; reset control and restart.
215	LOW COOLANT LVL	Indicates engine coolant level has fallen below the trip point. LOW COOLANT LVL Shutdown will not occur if genset is in Idle mode (low coolant warning only).	Shutdown	Check coolant level in radiator and recovery bottle and replenish if low; check defective coolant bottle hose or radiator cap; reset control and restart after correcting problem. Will not occur in Idle mode.
220	MAG PICKUP	Mag pickup speed indication is not being sensed or does not match generator set output frequency.	Shutdown	Restart and check RPM on the digital display; isolate per troubleshooting table 4-18.
221	FAIL TO CRANK	Possible fault with control or starting system; engine will not crank.	Shutdown	Check fuse F3 on the Engine Interface board; clean battery cable connections; recharge or replace battery.
222	OVERCRANK	Possible fuel system problem; engine stops cranking.	Shutdown	Check for empty fuel tank, fuel leaks, or plugged fuel lines; check/replace dirty fuel filter and air filter; reset and restart.
223	OVERSPEED	Indicates engine has exceeded normal operating speed (115% ±1% of nominal).	Shutdown	Inspect the mechanical fuel linkage and repair or replace; check the EFC for binding or damage; monitor the PCC duty cycle display and replace A32 or A38 as indicated.
224	FAIL TO SYNCHRONIZE	The generator set has not synchronized to the system bus within the allowable time frame.		Check governor system stability and adjust governing/synchronizer parameters; check for fuel system problems causing engine instability; widen synchronizing window and reduce acceptance time delay.
226	FAIL TO CLOSE	Indicates that the paralleling breaker has been given a signal to close, but has not closed properly.		Verify charging mechanism of paralleling breaker; check the close signal to the breaker; verify auxiliary contact signals from the breaker to the control are operational.
230	LOW DC VOLTAGE	Indicates battery voltage is below 10 VDC.	Warning	Recharge or replace battery; clean/tighten connections; check engine DC alternator; check battery charger float level.
231	HIGH DC VOLTAGE	Indicates battery voltage exceeds 32 VDC.	Warning	Check voltage float level on battery charger if applicable (lower float level); check engine DC alternator and replace if normal battery charging voltage is not obtained.
232	WEAK BATTERY	Indicates battery voltage drops below 60% of nominal for two seconds, during starting.	Warning	Recharge or replace the battery; see 230 LOW DC VOLTAGE.
240	LOW FUEL-DAY	Indicates day tank fuel supply is running low.	Warning	Check fuel supply and replenish as required.
241	LOW FUEL	Indicates fuel supply is running low.	Warning	Check fuel supply and replenish as required.
250	EEPROM ERROR	PCC memory error; data corruption of critical operating parameters.	Shutdown	Perform the initial start setup procedure; if shutdown repeats, replace the digital board (A32).
251	EEPROM ERROR	PCC memory error; data corruption of noncritical operating parameters.	Warning	Perform the adjustment procedures and save; if the same EEPROM ERROR occurs, perform the calibration procedures; if it still occurs, 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 EEPROM ERROR message occurs, replace the digital board (A32).
260	CUSTOMER FAULT 1	Customer defined input closed to ground; the nature of the fault is an optional customer selection which can be programmed to initiate a shutdown or a warning. Default message is editable.	Warning	Isolate the source of the false signal; disconnect the signal lead near the control and reset; if the message drops out there is a short to ground in the external wiring; if it remains replace A34. Customer fault messages are editable.
261	GROUND FAULT	Customer defined input closed to ground; the nature of the fault is an optional customer selection. Default message is editable.	Warning	Isolate the source of the false signal; check the corresponding customer interface board LED; disconnect the signal lead and reset the control; replace A34 or A32 as indicated.
262	RUPTURE BASIN / DAY TANK	Customer defined input closed to ground; the nature of the fault is an optional customer selection. Default message is editable.	Warning	Isolate the source of the false signal; check the corresponding customer interface board LED; disconnect the signal lead and reset the control; replace A34 or A32 as indicated.
263	HIGH GEN TEMP	Customer defined input closed to ground; the nature of the fault is an optional customer selection. Default message is editable.	Warning	Isolate the source of the false signal; check the corresponding customer interface board LED; disconnect the signal lead and reset the control; replace A34 or A32 as indicated.
270	PHASE ROTATION	The phase relationship between the generator set and the system bus is not matched.	Shutdown	Using a phase rotation checker, verify that the generator set phase rotation matches the system bus; verify control wiring to the bus PT module is properly connected.
272	FIRST START	The PowerCommand control is not receiving a proper signal from the system master first start sensor.	Warning	Control reverts to fallback mode; verify the Master First Start Sensor is functioning and that the voltage pulse is present at the PowerCommand control (terminal TB1-50); check interconnection wiring.
301	HIGH AC VOLTAGE	One or more phase voltages has exceeded 130% of nominal, or has exceeded 110% of nominal for 10 seconds.	Shutdown	Set the display to GEN VOLTS L-N and observe; determine if the output voltage the control sees is low or high; isolate to the PCC, alternator, PT/CT module (A36), customer interface board (A34), analog board (A33) or digital board (A32).
303	LOW AC VOLTAGE	One or more of the phase voltages has dropped below 85% of nominal for 10 seconds.	Shutdown	Check and repair the PMG or field wiring; check rotating rectifier diodes; check the load and correct any overload; check connectors J8 and J9 on A36, J3 and J5 on A34, and J7 on A37; isolate to A33, A32, A37 or A31.
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; isolate governor output module (A38), A32 or A31.
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	Indicates that power is flowing into the generator set rather than out from the unit.	Shutdown	Verify connection of generator set CT's; verify proper connection of load sharing lines; verify correct frequency and voltage on all sets.
337	LOSS OF EXCITATION	Indicates that the alternator excitation system is improperly adjusted or has failed.	Shutdown	Check output voltage with calibrated meter and adjust; check load sharing lines; see Section 6 Servicing the Generator.
BASIN	Day tank BASIN lamp	Fuel has overflowed into the rupture basin, indicating possible failure of pump-off and hi-fuel float switches or a leak in the day tank	Warning	RESET the control after fuel in the basin is safely disposed of and cause of overflow corrected
BLANK	Blank lamp	For customer use
F1	ECM fuse F1	Starter solenoid circuit, 20 amps		Replace with a fuse of the same type and amp rating
F2	ECM fuse F2	Fuel solenoid (switched B+) circuits, 20 amps		Replace with a fuse of the same type and amp rating
F3	ECM fuse F3	Continuous B+ out to remote circuits, 15 amps		Replace with a fuse of the same type and amp rating
F4	ECM fuse F4	ECM circuits, 5 amps		Replace with a fuse of the same type and amp rating
F5	ECM fuse F5	Engine gauge circuits, 5 amps		Replace with a fuse of the same type and amp rating
Fault 1 (Red)	Fault 1 (Detector-12)	Engine shut down because of a system fault; part of a 10 second time delay shutdown circuit (customer connections)	Shutdown	Service as required; selection jumpers may choose warning only or non-timed shutdown
Fault 2 (Red)	Fault 2 (Detector-12)	Engine shut down because of a system fault; part of a non-time delay shutdown circuit (customer connections)	Shutdown	Service as required; selection jumpers may choose warning only or 10 second time delay shutdown
HI FUEL	Day tank HI FUEL lamp	Fuel in the day tank has reached an abnormally high level, indicating possible failure of the pump-off float switch	Warning	High-fuel float switch takes over as automatic pump-off switch; reset when level drops to normal
High Engine Temperature (Red)	High Engine Temperature shutdown	Engine shut down because of excessively high engine coolant temperature (greater than 230 F)	Shutdown	Reset ECM; fill coolant as necessary and repair all leaks
LO FUEL	Day tank LO FUEL lamp	Fuel in the day tank has dropped to an abnormally low level, indicating possible failure of the pump-on float switch	Warning	Lo-fuel float switch takes over as automatic pump-on switch; reset when level rises to normal
LO SHUTDOWN	Day tank LO SHUTDOWN lamp	Fuel has dropped to a level near the bottom of the tank (empty main tank, pump failure, or float switch failure)	Shutdown	Check and fill main fuel tank; RESET both pump control and engine control
Low Engine Temperature (Yellow)	Low Engine Temperature (Detector-12)	Engine temperature is less than 70 F; possibility the engine might not start	Warning	Plug in, repair or install engine coolant and engine oil heaters
Low Fuel (Yellow)	Low Fuel (Detector-12)	Fuel level in the supply tank has dropped below reserve necessary for full load	Warning	Fill the main fuel supply tank with the appropriate grade of fuel
Low Oil Pressure (Red)	Low Oil Pressure shutdown	Engine shut down because of excessively low engine oil pressure (less than 14 psi)	Shutdown	Reset ECM (Stop then Reset); fill engine oil as necessary and repair all oil leaks
Overcrank (Red)	Overcrank shutdown	Engine shut down because it did not start during the timed cranking period (approximately 75 seconds, including two rest periods)	Shutdown	Reset control (Stop then Reset), then push Run or Remote
Overspeed (Red)	Overspeed shutdown	Engine shut down because of overspeed	Shutdown	Adjust cutout speed or replace overspeed module/switch; check governor and speed pickup
Pre High Engine Temperature (Yellow)	Pre High Engine Temperature	Engine coolant temperature is abnormally high (greater than 220 F)	Warning	Shut down the set if possible or disconnect non-critical loads; service engine cooling system
Pre Low Oil Pressure (Yellow)	Pre Low Oil Pressure	Engine oil pressure is abnormally low (less than 20 psi)	Warning	Shut down the set if possible or disconnect non-critical loads; service the engine lubricating system
Run (Green)	Run lamp	Generator set is running and the starter has been disconnected	Info
Switch-off (Flashing Red)	Switch-off (Detector-12)	Run/Stop/Remote switch is in the Stop position, preventing remote automatic operation	Info	Push the Run-Stop-Remote switch to Run or 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

Convert Day Tank Controller 240 VAC to 120 VAC adjustment

Remove the two jumpers between terminals TB1-6 and TB1-7.
Connect one jumper between TB1-5 and TB1-6 and the other between TB1-7 and TB1-8.
Move selector switch S103 on the control PCB to the up position for 120V.
If equipped with a transformer, remove jumpers between H2 and H3 and connect one between H1 and H3 and the other between H2 and H4.

Day Tank Controller Conversion 240 VAC to 120 VAC adjustment

Remove the two jumpers between terminals TB1-6 and TB1-7 and connect one between TB1-5 and TB1-6 and the other between TB1-7 and TB1-8.
Move selector switch S103 on the control PCB to the up position for 120V.
On the control transformer, remove the two jumpers between terminals H2 and H3 and connect one between H1 and H3 and the other between H2 and H4.

Dip Adjustment adjustment

Turn the DIP pot clockwise to increase the voltage vs frequency slope for frequencies below the UFRO threshold.
Greater slope gives greater voltage roll off as frequency drops, easing large load pickup but increasing voltage dip.
Turn the pot fully counterclockwise to make the slope the same above and below the threshold frequency.

Dwell Adjustment adjustment

Turn the DWELL pot clockwise to increase dwell time (voltage recovery time when frequency dips below threshold).
Turn the DWELL pot fully counterclockwise to eliminate dwell.
With no dwell, voltage recovery follows engine speed recovery.

Governor Adjustments (Type A Electric Governor) adjustment

Set selector switch S1 to OFF, S2 to appropriate model position.
Set pots initially: Gain 20%, I 20%, D 30%, Droop 0%.
Start set, adjust Speed pot for required frequency (60Hz=1800RPM or 50Hz=1500RPM) at operating temperature.
Disconnect load, turn Gain pot to 100% or until unstable, then back off until stable.
Adjust D and I pots similarly; readjust Speed if necessary.
Push throttle to minimum speed, release and observe overshoot (2-5 Hz acceptable); adjust I pot to reduce overshoot or hunting.

Initial Start Setup adjustment

⚠ Selecting this menu resets all operating parameters to default values; perform only by technically qualified personnel.

Press RESET, MENU and PHASE SELECT simultaneously to invoke the Initial Start Setup menu.
Toggle the Standby/Prime option.
Select the correct generator set model, frequency and kW rating.
Select the correct nominal line-to-line output voltage.
Select DELTA or WYE.
Select SAVE to save changes; MAIN MENU is then displayed.

Operating PowerCommand in Droop Mode adjustment

Set the no load speed and voltage at the desired level (bus must be de-energized or disconnect Bus PT module).
Apply 100% load and adjust KW load sharing gain for desired full load frequency; adjust KVAR load sharing gain for desired full load voltage.
Repeat the process for other generator sets in the system.
Test the system with all available load and verify approximately equal load sharing at no load and maximum load.

Over / Under Voltage Module Recalibration adjustment

Remove the two screws securing the top to the case and withdraw the top assembly.
Adjust the UNDER setpoint SET pot to 75 percent.
Apply single-phase, 60 Hertz, 104.25 VAC across terminals L and N.
Adjust pot R25 on the PC board until the relay trips (de-energizes).
Adjust the OVER setpoint SET pot to 125 percent.
Apply single-phase, 60 Hertz, 173.75 VAC across terminals L and N.
Adjust pot R26 on the PC board until the relay trips (energizes).
Repeat until no adjustments are necessary, then reassemble the module.

Torque Tester / Current Transformer Installation Check adjustment

Verify the dot on the CT faces toward the generator.
Verify CT21 is on U load leads, CT22 on V load leads, CT23 on W load leads.
Verify the correct CT secondary terminal (pin 2 high voltage / pin 3 low voltage) is used.
Check CT/PT wiring if a 335 Reverse Power shutdown occurs.

UFRO (Under Frequency Roll Off) Adjustment adjustment

⚠ High voltage - use insulating protection

Note the red LED on the board lights when frequency dips below threshold.
Turn the UFRO pot clockwise to raise the threshold frequency.
Turn the UFRO pot counterclockwise to lower the threshold frequency.
Determine threshold frequency by lowering generator frequency until the LED lights.

Voltage and Voltage Stability Adjustments (AVR) adjustment

⚠ High voltage - use dry wooden platform or rubber insulating mat, dry clothing, no jewelry, elbow length insulating gloves

Measure generator output voltage while running without load at nominal frequency.
Lock the control panel voltage trimmer at its midpoint if it cannot provide enough adjustment.
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 under large load, turn the STABILITY pot clockwise until stable.
Check and readjust the VOLTS pot each time the STABILITY pot is readjusted.

Servicing the PMG diagnostic

⚠ Touching uninsulated high voltage parts can result in severe personal injury or death.

Tools: Wheatstone bridge, digital ohmmeter

Disconnect leads P2, P3, P4 from voltage regulator.
Start engine and let speed stabilize.
Measure voltage across lead pairs P2-P3, P3-P4, P4-P2; should be at least 150 VAC (50Hz) or 180 VAC (60Hz).
Stop set and measure resistance across same lead pairs; each winding approximately 4.4 ohms.
Torque PMG rotor center bolt to 40 ft-lbs (54 Nm) when reassembling; stator leads must be at 12 o'clock.

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
		AVR response jumper	A to C	For generator output 90 kW or less (SX440 and MX321)
		Auxiliary terminal board TB21	K1, K2, P2, P3, P4, S2, S1, A2, A1	A1 and A2 connect a VAR/power factor controller when paralleling with a utility; S1 and S2 connect a droop compensating CT when paralleling with a generator set or utility
		Day tank LO SHUTDOWN engine shutdown connection	TB1-14 to engine block ground; TB1-15 to TB2-16 on the ECM
		Fault relay K8/K9 (Dry Contact Module)	K8=Over Crank, Low Oil Pressure, High Engine Temperature, Low Coolant Level, Low Fuel Level; K9=Low Fuel Level, Rupture Basin	Contact ratings: 40A max carry/break N.O. 12V coil, 30A N.C. 12V coil, 20A N.O./10A N.C. 24V coil
		MX321 PMG-excited jumper positions	2-3, 4-5 and 6-7	These jumpers must be in these positions
		MX321 voltage regulator frequency jumper	3-2 for 50 Hz; 3-1 for 60 Hz
		SX440 voltage regulator frequency jumper	C-50 for 50 Hz; C-60 for 60 Hz
		TB3 (ECM alternative RUN/STOP/REMOTE connection)	TB3-1=REMOTE, TB3-2=RUN, TB3-3=STOP	Provides alternative direct connection to ECM for troubleshooting or customer connection
		Voltage trimmer R21	voltage regulator terminals 1 and 2	There must be a jumper between terminals 1 and 2 when voltage trimmer R21 is not used
	single phase	QSG-Series power distribution panel voltage selector switch S1 position	main output terminals	Rotary switch under lockable cover selects 120/240 VAC single phase
	single phase	Voltage regulator terminal 6	jumpered to terminal 8	When the generator is connected for single-phase output, terminal 6 is not connected to the isolation transformer
	three phase	QSG-Series power distribution panel voltage selector switch S1 position	main output terminals	Rotary switch selects 120/208 VAC three phase
120	single phase	Day tank fuel pump control power reconnection	move jumpers from TB1-6/TB1-7 to TB1-5/TB1-6 and TB1-7/TB1-8	Move selector switch S103 on the control PCB to the up position for 120 V (factory set for 240 V, S103 down)
24		Day tank fuel pump control logic power (two lead harness, no transformer)	TB1-19 to positive (+) 24 V starter motor solenoid; TB-20 to negative (-)	Provides 24 VDC for the control circuit
240	single phase	Day tank fuel pump control default factory connection	jumpers between terminals TB1-6 and TB1-7	Selector switch S103 on the control PCB in the down position for 240 V

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 6CT8.3G?

The Cummins/Onan 6CT8.3G engine has an oil capacity of 19.0 liters.

Which generators use the Cummins/Onan 6CT8.3G engine?

The Cummins/Onan 6CT8.3G powers 1 generator set(s), including Cummins/Onan DGEA.

How often should you change the oil in the Cummins/Onan 6CT8.3G?

The Cummins/Onan 6CT8.3G oil change interval is every 500 hours.

What is a common problem with the Cummins/Onan 6CT8.3G engine?

A commonly reported issue on generators using the Cummins/Onan 6CT8.3G is: The FAULT 1 or FAULT 2 fault lamp lights. Engine shuts down immediately, engine runs for several seconds and then shuts down, or engine continues to run.. Fix: The standard undesignated fault functions are programmed to shut down the set when a fault is sensed. Fault 1 is time delayed while Fault 2 is immediate. The nature of the fault is an optional selection that is determined when the set installation is designed. The undesignated fault functions may also be programmed for non-shutdown or non-time delay..